On 01.06.2018 01:16, Stefan Agner wrote: > Add support for the NAND flash controller found on NVIDIA > Tegra 2 SoCs. This implementation does not make use of the > command queue feature. Regular operations/data transfers are > done in PIO mode. Page read/writes with hardware ECC make > use of the DMA for data transfer. > > Signed-off-by: Lucas Stach <dev@xxxxxxxxxx> > Signed-off-by: Stefan Agner <stefan@xxxxxxxx> > --- > MAINTAINERS | 7 + > drivers/mtd/nand/raw/Kconfig | 6 + > drivers/mtd/nand/raw/Makefile | 1 + > drivers/mtd/nand/raw/tegra_nand.c | 1143 +++++++++++++++++++++++++++++ > 4 files changed, 1157 insertions(+) > create mode 100644 drivers/mtd/nand/raw/tegra_nand.c > > diff --git a/MAINTAINERS b/MAINTAINERS > index 58b9861ccf99..c2e5571c85d4 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -13844,6 +13844,13 @@ M: Laxman Dewangan <ldewangan@xxxxxxxxxx> > S: Supported > F: drivers/input/keyboard/tegra-kbc.c > > +TEGRA NAND DRIVER > +M: Stefan Agner <stefan@xxxxxxxx> > +M: Lucas Stach <dev@xxxxxxxxxx> > +S: Maintained > +F: Documentation/devicetree/bindings/mtd/nvidia-tegra20-nand.txt > +F: drivers/mtd/nand/raw/tegra_nand.c > + > TEGRA PWM DRIVER > M: Thierry Reding <thierry.reding@xxxxxxxxx> > S: Supported > diff --git a/drivers/mtd/nand/raw/Kconfig b/drivers/mtd/nand/raw/Kconfig > index 19a2b283fbbe..e9093f52371e 100644 > --- a/drivers/mtd/nand/raw/Kconfig > +++ b/drivers/mtd/nand/raw/Kconfig > @@ -534,4 +534,10 @@ config MTD_NAND_MTK > Enables support for NAND controller on MTK SoCs. > This controller is found on mt27xx, mt81xx, mt65xx SoCs. > > +config MTD_NAND_TEGRA > + tristate "Support for NAND controller on NVIDIA Tegra" > + depends on ARCH_TEGRA || COMPILE_TEST > + help > + Enables support for NAND flash controller on NVIDIA Tegra SoC. > + > endif # MTD_NAND > diff --git a/drivers/mtd/nand/raw/Makefile b/drivers/mtd/nand/raw/Makefile > index 165b7ef9e9a1..d5a5f9832b88 100644 > --- a/drivers/mtd/nand/raw/Makefile > +++ b/drivers/mtd/nand/raw/Makefile > @@ -56,6 +56,7 @@ obj-$(CONFIG_MTD_NAND_HISI504) += hisi504_nand.o > obj-$(CONFIG_MTD_NAND_BRCMNAND) += brcmnand/ > obj-$(CONFIG_MTD_NAND_QCOM) += qcom_nandc.o > obj-$(CONFIG_MTD_NAND_MTK) += mtk_ecc.o mtk_nand.o > +obj-$(CONFIG_MTD_NAND_TEGRA) += tegra_nand.o > > nand-objs := nand_base.o nand_bbt.o nand_timings.o nand_ids.o > nand-objs += nand_amd.o > diff --git a/drivers/mtd/nand/raw/tegra_nand.c b/drivers/mtd/nand/raw/tegra_nand.c > new file mode 100644 > index 000000000000..e9664f2938a3 > --- /dev/null > +++ b/drivers/mtd/nand/raw/tegra_nand.c > @@ -0,0 +1,1143 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright (C) 2018 Stefan Agner <stefan@xxxxxxxx> > + * Copyright (C) 2014-2015 Lucas Stach <dev@xxxxxxxxxx> > + * Copyright (C) 2012 Avionic Design GmbH > + */ > + > +#include <linux/clk.h> > +#include <linux/completion.h> > +#include <linux/delay.h> > +#include <linux/dma-mapping.h> > +#include <linux/err.h> > +#include <linux/gpio/consumer.h> > +#include <linux/interrupt.h> > +#include <linux/io.h> > +#include <linux/module.h> > +#include <linux/mtd/partitions.h> > +#include <linux/mtd/rawnand.h> > +#include <linux/of.h> > +#include <linux/platform_device.h> > +#include <linux/reset.h> > + > +#define CMD 0x00 > +#define CMD_GO BIT(31) > +#define CMD_CLE BIT(30) > +#define CMD_ALE BIT(29) > +#define CMD_PIO BIT(28) > +#define CMD_TX BIT(27) > +#define CMD_RX BIT(26) > +#define CMD_SEC_CMD BIT(25) > +#define CMD_AFT_DAT BIT(24) > +#define CMD_TRANS_SIZE(x) (((x - 1) & 0xf) << 20) > +#define CMD_A_VALID BIT(19) > +#define CMD_B_VALID BIT(18) > +#define CMD_RD_STATUS_CHK BIT(17) > +#define CMD_RBSY_CHK BIT(16) > +#define CMD_CE(x) BIT((8 + ((x) & 0x7))) > +#define CMD_CLE_SIZE(x) (((x - 1) & 0x3) << 4) > +#define CMD_ALE_SIZE(x) (((x - 1) & 0xf) << 0) > + > +#define STATUS 0x04 > + > +#define ISR 0x08 > +#define ISR_CORRFAIL_ERR BIT(24) > +#define ISR_UND BIT(7) > +#define ISR_OVR BIT(6) > +#define ISR_CMD_DONE BIT(5) > +#define ISR_ECC_ERR BIT(4) > + > +#define IER 0x0c > +#define IER_ERR_TRIG_VAL(x) (((x) & 0xf) << 16) > +#define IER_UND BIT(7) > +#define IER_OVR BIT(6) > +#define IER_CMD_DONE BIT(5) > +#define IER_ECC_ERR BIT(4) > +#define IER_GIE BIT(0) > + > +#define CFG 0x10 > +#define CFG_HW_ECC BIT(31) > +#define CFG_ECC_SEL BIT(30) > +#define CFG_ERR_COR BIT(29) > +#define CFG_PIPE_EN BIT(28) > +#define CFG_TVAL_4 (0 << 24) > +#define CFG_TVAL_6 (1 << 24) > +#define CFG_TVAL_8 (2 << 24) > +#define CFG_SKIP_SPARE BIT(23) > +#define CFG_BUS_WIDTH_16 BIT(21) > +#define CFG_COM_BSY BIT(20) > +#define CFG_PS_256 (0 << 16) > +#define CFG_PS_512 (1 << 16) > +#define CFG_PS_1024 (2 << 16) > +#define CFG_PS_2048 (3 << 16) > +#define CFG_PS_4096 (4 << 16) > +#define CFG_SKIP_SPARE_SIZE_4 (0 << 14) > +#define CFG_SKIP_SPARE_SIZE_8 (1 << 14) > +#define CFG_SKIP_SPARE_SIZE_12 (2 << 14) > +#define CFG_SKIP_SPARE_SIZE_16 (3 << 14) > +#define CFG_TAG_BYTE_SIZE(x) ((x) & 0xff) > + > +#define TIMING_1 0x14 > +#define TIMING_TRP_RESP(x) (((x) & 0xf) << 28) > +#define TIMING_TWB(x) (((x) & 0xf) << 24) > +#define TIMING_TCR_TAR_TRR(x) (((x) & 0xf) << 20) > +#define TIMING_TWHR(x) (((x) & 0xf) << 16) > +#define TIMING_TCS(x) (((x) & 0x3) << 14) > +#define TIMING_TWH(x) (((x) & 0x3) << 12) > +#define TIMING_TWP(x) (((x) & 0xf) << 8) > +#define TIMING_TRH(x) (((x) & 0x3) << 4) > +#define TIMING_TRP(x) (((x) & 0xf) << 0) > + > +#define RESP 0x18 > + > +#define TIMING_2 0x1c > +#define TIMING_TADL(x) ((x) & 0xf) > + > +#define CMD_1 0x20 > +#define CMD_2 0x24 > +#define ADDR_1 0x28 > +#define ADDR_2 0x2c > + > +#define DMA_CTRL 0x30 > +#define DMA_CTRL_GO BIT(31) > +#define DMA_CTRL_IN (0 << 30) > +#define DMA_CTRL_OUT BIT(30) > +#define DMA_CTRL_PERF_EN BIT(29) > +#define DMA_CTRL_IE_DONE BIT(28) > +#define DMA_CTRL_REUSE BIT(27) > +#define DMA_CTRL_BURST_1 (2 << 24) > +#define DMA_CTRL_BURST_4 (3 << 24) > +#define DMA_CTRL_BURST_8 (4 << 24) > +#define DMA_CTRL_BURST_16 (5 << 24) > +#define DMA_CTRL_IS_DONE BIT(20) > +#define DMA_CTRL_EN_A BIT(2) > +#define DMA_CTRL_EN_B BIT(1) > + > +#define DMA_CFG_A 0x34 > +#define DMA_CFG_B 0x38 > + > +#define FIFO_CTRL 0x3c > +#define FIFO_CTRL_CLR_ALL BIT(3) > + > +#define DATA_PTR 0x40 > +#define TAG_PTR 0x44 > +#define ECC_PTR 0x48 > + > +#define DEC_STATUS 0x4c > +#define DEC_STATUS_A_ECC_FAIL BIT(1) > +#define DEC_STATUS_ERR_COUNT_MASK 0x00ff0000 > +#define DEC_STATUS_ERR_COUNT_SHIFT 16 > + > +#define HWSTATUS_CMD 0x50 > +#define HWSTATUS_MASK 0x54 > +#define HWSTATUS_RDSTATUS_MASK(x) (((x) & 0xff) << 24) > +#define HWSTATUS_RDSTATUS_VALUE(x) (((x) & 0xff) << 16) > +#define HWSTATUS_RBSY_MASK(x) (((x) & 0xff) << 8) > +#define HWSTATUS_RBSY_VALUE(x) (((x) & 0xff) << 0) > + > +#define BCH_CONFIG 0xcc > +#define BCH_ENABLE BIT(0) > +#define BCH_TVAL_4 (0 << 4) > +#define BCH_TVAL_8 (1 << 4) > +#define BCH_TVAL_14 (2 << 4) > +#define BCH_TVAL_16 (3 << 4) > + > +#define DEC_STAT_RESULT 0xd0 > +#define DEC_STAT_BUF 0xd4 > +#define DEC_STAT_BUF_FAIL_SEC_FLAG_MASK 0xff000000 > +#define DEC_STAT_BUF_FAIL_SEC_FLAG_SHIFT 24 > +#define DEC_STAT_BUF_CORR_SEC_FLAG_MASK 0x00ff0000 > +#define DEC_STAT_BUF_CORR_SEC_FLAG_SHIFT 16 > +#define DEC_STAT_BUF_MAX_CORR_CNT_MASK 0x00001f00 > +#define DEC_STAT_BUF_MAX_CORR_CNT_SHIFT 8 > + > +#define OFFSET(val, off) ((val) < (off) ? 0 : (val) - (off)) > + > +#define SKIP_SPARE_BYTES 4 > +#define BITS_PER_STEP_RS 18 > +#define BITS_PER_STEP_BCH 13 > + > +struct tegra_nand_controller { > + struct nand_hw_control controller; > + void __iomem *regs; > + struct clk *clk; > + struct device *dev; > + struct completion command_complete; > + struct completion dma_complete; > + bool last_read_error; > + int cur_chip; > + struct nand_chip *chip; > +}; > + > +struct tegra_nand_chip { > + struct nand_chip chip; > + struct gpio_desc *wp_gpio; > + struct mtd_oob_region tag; > +}; > + > +static inline struct tegra_nand_controller *to_tegra_ctrl( > + struct nand_hw_control *hw_ctrl) > +{ > + return container_of(hw_ctrl, struct tegra_nand_controller, controller); > +} > + > +static inline struct tegra_nand_chip *to_tegra_chip(struct nand_chip *chip) > +{ > + return container_of(chip, struct tegra_nand_chip, chip); > +} > + > +static int tegra_nand_ooblayout_rs_ecc(struct mtd_info *mtd, int section, > + struct mtd_oob_region *oobregion) > +{ > + struct nand_chip *chip = mtd_to_nand(mtd); > + int bytes_per_step = DIV_ROUND_UP(BITS_PER_STEP_RS * chip->ecc.strength, > + BITS_PER_BYTE); > + > + if (section > 0) > + return -ERANGE; > + > + oobregion->offset = SKIP_SPARE_BYTES; > + oobregion->length = round_up(bytes_per_step * chip->ecc.steps, 4); > + > + return 0; > +} > + > +static int tegra_nand_ooblayout_rs_free(struct mtd_info *mtd, int section, > + struct mtd_oob_region *oobregion) > +{ > + struct nand_chip *chip = mtd_to_nand(mtd); > + int bytes_per_step = DIV_ROUND_UP(BITS_PER_STEP_RS * chip->ecc.strength, > + BITS_PER_BYTE); > + > + if (section > 0) > + return -ERANGE; > + > + oobregion->offset = SKIP_SPARE_BYTES + > + round_up(bytes_per_step * chip->ecc.steps, 4); > + oobregion->length = mtd->oobsize - oobregion->offset; > + > + return 0; > +} > + > +static const struct mtd_ooblayout_ops tegra_nand_oob_rs_ops = { > + .ecc = tegra_nand_ooblayout_rs_ecc, > + .free = tegra_nand_ooblayout_rs_free, > +}; > + > +static int tegra_nand_ooblayout_bch_ecc(struct mtd_info *mtd, int section, > + struct mtd_oob_region *oobregion) > +{ > + struct nand_chip *chip = mtd_to_nand(mtd); > + int bytes_per_step = DIV_ROUND_UP(BITS_PER_STEP_BCH * chip->ecc.strength, > + BITS_PER_BYTE); > + > + if (section > 0) > + return -ERANGE; > + > + oobregion->offset = SKIP_SPARE_BYTES; > + oobregion->length = round_up(bytes_per_step * chip->ecc.steps, 4); > + > + return 0; > +} > + > +static int tegra_nand_ooblayout_bch_free(struct mtd_info *mtd, int section, > + struct mtd_oob_region *oobregion) > +{ > + struct nand_chip *chip = mtd_to_nand(mtd); > + int bytes_per_step = DIV_ROUND_UP(BITS_PER_STEP_BCH * chip->ecc.strength, > + BITS_PER_BYTE); > + > + if (section > 0) > + return -ERANGE; > + > + oobregion->offset = SKIP_SPARE_BYTES + > + round_up(bytes_per_step * chip->ecc.steps, 4); > + oobregion->length = mtd->oobsize - oobregion->offset; > + > + return 0; > +} > + > +/* > + * Layout with tag bytes is > + * > + * -------------------------------------------------------------------------- > + * | main area | skip bytes | tag bytes | parity | .. | > + * -------------------------------------------------------------------------- > + * > + * If not tag bytes are written, parity moves right after skip bytes! > + */ > +static const struct mtd_ooblayout_ops tegra_nand_oob_bch_ops = { > + .ecc = tegra_nand_ooblayout_bch_ecc, > + .free = tegra_nand_ooblayout_bch_free, > +}; > + > +static irqreturn_t tegra_nand_irq(int irq, void *data) > +{ > + struct tegra_nand_controller *ctrl = data; > + u32 isr, dma; > + > + isr = readl_relaxed(ctrl->regs + ISR); > + dma = readl_relaxed(ctrl->regs + DMA_CTRL); > + dev_dbg(ctrl->dev, "isr %08x\n", isr); > + > + if (!isr && !(dma & DMA_CTRL_IS_DONE)) > + return IRQ_NONE; > + > + /* > + * The bit name is somewhat missleading: This is also set when > + * HW ECC was successful. The data sheet states: > + * Correctable OR Un-correctable errors occurred in the DMA transfer... > + */ > + if (isr & ISR_CORRFAIL_ERR) > + ctrl->last_read_error = true; > + > + if (isr & ISR_CMD_DONE) > + complete(&ctrl->command_complete); > + > + if (isr & ISR_UND) > + dev_err(ctrl->dev, "FIFO underrun\n"); > + > + if (isr & ISR_OVR) > + dev_err(ctrl->dev, "FIFO overrun\n"); > + > + /* handle DMA interrupts */ > + if (dma & DMA_CTRL_IS_DONE) { > + writel_relaxed(dma, ctrl->regs + DMA_CTRL); > + complete(&ctrl->dma_complete); > + } > + > + /* clear interrupts */ > + writel_relaxed(isr, ctrl->regs + ISR); > + > + return IRQ_HANDLED; > +} > + > +static const char * const tegra_nand_reg_names[] = { > + "COMMAND", > + "STATUS", > + "ISR", > + "IER", > + "CONFIG", > + "TIMING", > + NULL, > + "TIMING2", > + "CMD_REG1", > + "CMD_REG2", > + "ADDR_REG1", > + "ADDR_REG2", > + "DMA_MST_CTRL", > + "DMA_CFG_A", > + "DMA_CFG_B", > + "FIFO_CTRL", > +}; > + > +static void tegra_nand_dump_reg(struct tegra_nand_controller *ctrl) > +{ > + u32 reg; > + int i; > + > + dev_err(ctrl->dev, "Tegra NAND controller register dump\n"); > + for (i = 0; i < ARRAY_SIZE(tegra_nand_reg_names); i++) { > + const char *reg_name = tegra_nand_reg_names[i]; > + > + if (!reg_name) > + continue; > + > + reg = readl_relaxed(ctrl->regs + (i * 4)); > + dev_err(ctrl->dev, "%s: 0x%08x\n", reg_name, reg); > + } > +} > + > +static int tegra_nand_cmd(struct nand_chip *chip, > + const struct nand_subop *subop) > +{ > + const struct nand_op_instr *instr; > + const struct nand_op_instr *instr_data_in = NULL; > + struct tegra_nand_controller *ctrl = to_tegra_ctrl(chip->controller); > + unsigned int op_id, size = 0, offset = 0; > + bool first_cmd = true; > + u32 reg, cmd = 0; > + int ret; > + > + for (op_id = 0; op_id < subop->ninstrs; op_id++) { > + unsigned int naddrs, i; > + const u8 *addrs; > + u32 addr1 = 0, addr2 = 0; > + > + instr = &subop->instrs[op_id]; > + > + switch (instr->type) { > + case NAND_OP_CMD_INSTR: > + if (first_cmd) { > + cmd |= CMD_CLE; > + writel_relaxed(instr->ctx.cmd.opcode, > + ctrl->regs + CMD_1); > + } else { > + cmd |= CMD_SEC_CMD; > + writel_relaxed(instr->ctx.cmd.opcode, > + ctrl->regs + CMD_2); > + } > + first_cmd = false; > + break; > + case NAND_OP_ADDR_INSTR: > + offset = nand_subop_get_addr_start_off(subop, op_id); > + naddrs = nand_subop_get_num_addr_cyc(subop, op_id); > + addrs = &instr->ctx.addr.addrs[offset]; > + > + cmd |= CMD_ALE | CMD_ALE_SIZE(naddrs); > + for (i = 0; i < min_t(unsigned int, 4, naddrs); i++) > + addr1 |= *addrs++ << (BITS_PER_BYTE * i); > + naddrs -= i; > + for (i = 0; i < min_t(unsigned int, 4, naddrs); i++) > + addr2 |= *addrs++ << (BITS_PER_BYTE * i); > + writel_relaxed(addr1, ctrl->regs + ADDR_1); > + writel_relaxed(addr2, ctrl->regs + ADDR_2); > + break; > + > + case NAND_OP_DATA_IN_INSTR: > + size = nand_subop_get_data_len(subop, op_id); > + offset = nand_subop_get_data_start_off(subop, op_id); > + > + cmd |= CMD_TRANS_SIZE(size) | CMD_PIO | CMD_RX | > + CMD_A_VALID; > + > + instr_data_in = instr; > + break; > + > + case NAND_OP_DATA_OUT_INSTR: > + size = nand_subop_get_data_len(subop, op_id); > + offset = nand_subop_get_data_start_off(subop, op_id); > + > + cmd |= CMD_TRANS_SIZE(size) | CMD_PIO | CMD_TX | > + CMD_A_VALID; > + > + memcpy(®, instr->ctx.data.buf.out + offset, size); > + writel_relaxed(reg, ctrl->regs + RESP); > + > + break; > + case NAND_OP_WAITRDY_INSTR: > + cmd |= CMD_RBSY_CHK; > + break; > + > + } > + } > + > + cmd |= CMD_GO | CMD_CE(ctrl->cur_chip); > + writel_relaxed(cmd, ctrl->regs + CMD); > + ret = wait_for_completion_timeout(&ctrl->command_complete, > + msecs_to_jiffies(500)); > + if (!ret) { > + dev_err(ctrl->dev, "CMD timeout\n"); > + tegra_nand_dump_reg(ctrl); > + return -ETIMEDOUT; > + } - wait_for_completion_timeout() could fail - HW shall be reset - completion shall be re-inited because IRQ could fire just after the completion timeout I'd write it something like this: #define INT_MASK (IER_UND | IER_OVR | IER_CMD_DONE | IER_GIE) #define HWSTATUS_MASK (HWSTATUS_RDSTATUS_MASK(1) | \ HWSTATUS_RDSTATUS_VALUE(0) | \ HWSTATUS_RBSY_MASK(NAND_STATUS_READY) | \ HWSTATUS_RBSY_VALUE(NAND_STATUS_READY)) #define HW_TIMEOUT 500 void tegra_nand_controller_reset(struct tegra_nand_controller *ctrl) { int err; disable_irq(ctrl->irq); err = reset_control_reset(ctrl->rst); if (err) { dev_err(ctrl->dev, "Failed to reset HW: %d\n", err); msleep(HW_TIMEOUT); } writel_relaxed(NAND_CMD_STATUS, ctrl->regs + HWSTATUS_CMD); writel_relaxed(HWSTATUS_MASK, ctrl->regs + HWSTATUS_MASK); writel_relaxed(INT_MASK, ctrl->regs + ISR); reinit_completion(&ctrl->command_complete); reinit_completion(&ctrl->dma_complete); enable_irq(ctrl->irq); } ... ret = wait_for_completion_timeout(&ctrl->command_complete, msecs_to_jiffies(HW_TIMEOUT)); if (ret <= 0) { if (ret == 0) { dev_err(ctrl->dev, "CMD timeout\n"); tegra_nand_dump_reg(ctrl); ret = -ETIMEDOUT; } else { dev_err(ctrl->dev, "Failed to wait for CMD completion: %d\n", ret); } tegra_nand_controller_reset(ctrl); return ret; } > + > + if (instr_data_in) { > + reg = readl_relaxed(ctrl->regs + RESP); > + memcpy(instr_data_in->ctx.data.buf.in + offset, ®, size); > + } > + > + return 0; > +} > + > +static const struct nand_op_parser tegra_nand_op_parser = NAND_OP_PARSER( > + NAND_OP_PARSER_PATTERN(tegra_nand_cmd, > + NAND_OP_PARSER_PAT_CMD_ELEM(true), > + NAND_OP_PARSER_PAT_ADDR_ELEM(true, 8), > + NAND_OP_PARSER_PAT_CMD_ELEM(true), > + NAND_OP_PARSER_PAT_WAITRDY_ELEM(true)), > + NAND_OP_PARSER_PATTERN(tegra_nand_cmd, > + NAND_OP_PARSER_PAT_DATA_OUT_ELEM(false, 4)), > + NAND_OP_PARSER_PATTERN(tegra_nand_cmd, > + NAND_OP_PARSER_PAT_CMD_ELEM(true), > + NAND_OP_PARSER_PAT_ADDR_ELEM(true, 8), > + NAND_OP_PARSER_PAT_CMD_ELEM(true), > + NAND_OP_PARSER_PAT_WAITRDY_ELEM(true), > + NAND_OP_PARSER_PAT_DATA_IN_ELEM(true, 4)), > + ); > + > +static int tegra_nand_exec_op(struct nand_chip *chip, > + const struct nand_operation *op, > + bool check_only) > +{ > + return nand_op_parser_exec_op(chip, &tegra_nand_op_parser, op, > + check_only); > +} > +static void tegra_nand_select_chip(struct mtd_info *mtd, int chip_nr) > +{ > + struct nand_chip *chip = mtd_to_nand(mtd); > + struct tegra_nand_controller *ctrl = to_tegra_ctrl(chip->controller); > + > + ctrl->cur_chip = chip_nr; > +} > + > +static void tegra_nand_hw_ecc(struct tegra_nand_controller *ctrl, > + struct nand_chip *chip, bool enable) > +{ > + u32 reg; > + > + switch (chip->ecc.algo) { > + case NAND_ECC_RS: > + reg = readl_relaxed(ctrl->regs + CFG); > + if (enable) > + reg |= CFG_HW_ECC | CFG_ERR_COR; > + else > + reg &= ~(CFG_HW_ECC | CFG_ERR_COR); > + writel_relaxed(reg, ctrl->regs + CFG); > + break; > + case NAND_ECC_BCH: > + reg = readl_relaxed(ctrl->regs + BCH_CONFIG); > + if (enable) > + reg |= BCH_ENABLE; > + else > + reg &= ~BCH_ENABLE; > + writel_relaxed(reg, ctrl->regs + BCH_CONFIG); > + break; > + default: > + dev_err(ctrl->dev, "Unsupported hardware ECC algorithm\n"); > + break; > + } > +} > + > +static int tegra_nand_page_xfer(struct mtd_info *mtd, struct nand_chip *chip, > + void *buf, int oob_required, int page, > + bool read) > +{ > + struct tegra_nand_controller *ctrl = to_tegra_ctrl(chip->controller); > + struct tegra_nand_chip *nand = to_tegra_chip(chip); > + enum dma_data_direction dir = read ? DMA_FROM_DEVICE : DMA_TO_DEVICE; > + dma_addr_t dma_addr; > + u32 cmd, dma_ctrl; > + int ret, dma_len; > + > + if (read) { > + writel_relaxed(NAND_CMD_READ0, ctrl->regs + CMD_1); > + writel_relaxed(NAND_CMD_READSTART, ctrl->regs + CMD_2); > + } else { > + writel_relaxed(NAND_CMD_SEQIN, ctrl->regs + CMD_1); > + writel_relaxed(NAND_CMD_PAGEPROG, ctrl->regs + CMD_2); > + } > + cmd = CMD_CLE | CMD_SEC_CMD; > + > + /* Lower 16-bits are column, always 0 */ > + writel_relaxed(page << 16, ctrl->regs + ADDR_1); > + > + if (chip->options & NAND_ROW_ADDR_3) { > + writel_relaxed(page >> 16, ctrl->regs + ADDR_2); > + cmd |= CMD_ALE | CMD_ALE_SIZE(5); > + } else { > + cmd |= CMD_ALE | CMD_ALE_SIZE(4); > + } > + > + dma_len = mtd->writesize + (oob_required ? mtd->oobsize : 0); > + dma_addr = dma_map_single(ctrl->dev, buf, dma_len, dir); > + ret = dma_mapping_error(ctrl->dev, dma_addr); > + if (ret) { > + dev_err(ctrl->dev, "dma mapping error\n"); > + return -EINVAL; > + } > + > + writel_relaxed(mtd->writesize - 1, ctrl->regs + DMA_CFG_A); > + writel_relaxed(dma_addr, ctrl->regs + DATA_PTR); > + > + if (oob_required) { > + dma_addr_t dma_addr_tag = dma_addr + mtd->writesize; > + > + writel_relaxed(nand->tag.length - 1, ctrl->regs + DMA_CFG_B); > + writel_relaxed(dma_addr_tag + nand->tag.offset, > + ctrl->regs + TAG_PTR); > + } else { > + writel_relaxed(0, ctrl->regs + DMA_CFG_B); > + writel_relaxed(0, ctrl->regs + TAG_PTR); > + } > + > + dma_ctrl = DMA_CTRL_GO | DMA_CTRL_PERF_EN | > + DMA_CTRL_IE_DONE | DMA_CTRL_IS_DONE | > + DMA_CTRL_BURST_16 | DMA_CTRL_EN_A; > + if (oob_required) > + dma_ctrl |= DMA_CTRL_EN_B; > + if (read) > + dma_ctrl |= DMA_CTRL_IN | DMA_CTRL_REUSE; > + else > + dma_ctrl |= DMA_CTRL_OUT; > + > + writel_relaxed(dma_ctrl, ctrl->regs + DMA_CTRL); > + > + cmd |= CMD_GO | CMD_RBSY_CHK | CMD_TRANS_SIZE(9) | > + CMD_CE(ctrl->cur_chip) | CMD_A_VALID; > + if (oob_required) > + cmd |= CMD_B_VALID; > + if (read) > + cmd |= CMD_RX; > + else > + cmd |= CMD_TX | CMD_AFT_DAT; > + > + writel_relaxed(cmd, ctrl->regs + CMD); > + > + ret = wait_for_completion_timeout(&ctrl->command_complete, > + msecs_to_jiffies(500)); > + if (!ret) { > + dev_err(ctrl->dev, "CMD timeout\n"); > + tegra_nand_dump_reg(ctrl); > + ret = -ETIMEDOUT; > + goto err_unmap_dma; > + } > + > + ret = wait_for_completion_timeout(&ctrl->dma_complete, > + msecs_to_jiffies(500)); > + if (!ret) { > + dev_err(ctrl->dev, "DMA timeout\n"); > + tegra_nand_dump_reg(ctrl); > + ret = -ETIMEDOUT; > + goto err_unmap_dma; > + } > + ret = 0; Same as the above comment regarding the wait_for_completion_timeout(). > + > +err_unmap_dma: > + dma_unmap_single(ctrl->dev, dma_addr, dma_len, dir); > + > + return ret; > +} > + > +static int tegra_nand_read_page_hwecc(struct mtd_info *mtd, > + struct nand_chip *chip, > + uint8_t *buf, int oob_required, int page) > +{ > + struct tegra_nand_controller *ctrl = to_tegra_ctrl(chip->controller); > + u32 dec_stat, max_corr_cnt; > + unsigned long fail_sec_flag; > + int ret; > + > + tegra_nand_hw_ecc(ctrl, chip, true); > + ret = tegra_nand_page_xfer(mtd, chip, buf, oob_required, page, true); > + tegra_nand_hw_ecc(ctrl, chip, false); > + if (ret) > + return ret; > + > + /* No correctable or un-correctable errors, page must have 0 bitflips */ > + if (!ctrl->last_read_error) > + return 0; > + > + /* > + * Correctable or un-correctable errors occurred. Use DEC_STAT_BUF > + * which contains information for all ECC selections. > + * > + * Note that since we do not use Command Queues DEC_RESULT does not > + * state the number of pages we can read from the DEC_STAT_BUF. But > + * since CORRFAIL_ERR did occur during page read we do have a valid > + * result in DEC_STAT_BUF. > + */ > + ctrl->last_read_error = false; > + dec_stat = readl_relaxed(ctrl->regs + DEC_STAT_BUF); > + > + fail_sec_flag = (dec_stat & DEC_STAT_BUF_FAIL_SEC_FLAG_MASK) >> > + DEC_STAT_BUF_FAIL_SEC_FLAG_SHIFT; > + > + max_corr_cnt = (dec_stat & DEC_STAT_BUF_MAX_CORR_CNT_MASK) >> > + DEC_STAT_BUF_MAX_CORR_CNT_SHIFT; > + > + if (fail_sec_flag) { > + int bit, max_bitflips = 0; > + > + /* > + * Check if all sectors in a page failed. If only some failed > + * its definitly not an erased page and we can return error > + * stats right away. > + * > + * E.g. controller might return fail_sec_flag with 0x4, which > + * would mean only the third sector failed to correct. > + */ > + if (fail_sec_flag ^ GENMASK(chip->ecc.steps - 1, 0)) { > + mtd->ecc_stats.failed += hweight8(fail_sec_flag); > + return max_corr_cnt; > + } > + > + /* > + * All sectors failed to correct, but the ECC isn't smart > + * enough to figure out if a page is really completely erased. > + * We check the read data here to figure out if it's a > + * legitimate ECC error or only an erased page. > + */ > + for_each_set_bit(bit, &fail_sec_flag, chip->ecc.steps) { > + u8 *data = buf + (chip->ecc.size * bit); > + > + ret = nand_check_erased_ecc_chunk(data, chip->ecc.size, > + NULL, 0, > + NULL, 0, > + chip->ecc.strength); > + if (ret < 0) > + mtd->ecc_stats.failed++; > + else > + max_bitflips = max(ret, max_bitflips); > + } > + > + return max_t(unsigned int, max_corr_cnt, max_bitflips); > + } else { > + int corr_sec_flag; > + > + corr_sec_flag = (dec_stat & DEC_STAT_BUF_CORR_SEC_FLAG_MASK) >> > + DEC_STAT_BUF_CORR_SEC_FLAG_SHIFT; > + > + /* > + * The value returned in the register is the maximum of > + * bitflips encountered in any of the ECC regions. As there is > + * no way to get the number of bitflips in a specific regions > + * we are not able to deliver correct stats but instead > + * overestimate the number of corrected bitflips by assuming > + * that all regions where errors have been corrected > + * encountered the maximum number of bitflips. > + */ > + mtd->ecc_stats.corrected += max_corr_cnt * hweight8(corr_sec_flag); > + > + return max_corr_cnt; > + } > + > +} > + > +static int tegra_nand_write_page_hwecc(struct mtd_info *mtd, > + struct nand_chip *chip, > + const uint8_t *buf, int oob_required, > + int page) > +{ > + struct tegra_nand_controller *ctrl = to_tegra_ctrl(chip->controller); > + int ret; > + > + tegra_nand_hw_ecc(ctrl, chip, true); > + ret = tegra_nand_page_xfer(mtd, chip, (void *)buf, oob_required, page, > + false); > + tegra_nand_hw_ecc(ctrl, chip, false); > + > + return ret; > +} > + > +static void tegra_nand_setup_timing(struct tegra_nand_controller *ctrl, > + const struct nand_sdr_timings *timings) > +{ > + /* > + * The period (and all other timings in this function) is in ps, > + * so need to take care here to avoid integer overflows. > + */ > + unsigned int rate = clk_get_rate(ctrl->clk) / 1000000; > + unsigned int period = DIV_ROUND_UP(1000000, rate); > + u32 val, reg = 0; > + > + val = DIV_ROUND_UP(max3(timings->tAR_min, timings->tRR_min, > + timings->tRC_min), period); > + reg |= TIMING_TCR_TAR_TRR(OFFSET(val, 3)); > + > + val = DIV_ROUND_UP(max(max(timings->tCS_min, timings->tCH_min), > + max(timings->tALS_min, timings->tALH_min)), > + period); > + reg |= TIMING_TCS(OFFSET(val, 2)); > + > + val = DIV_ROUND_UP(max(timings->tRP_min, timings->tREA_max) + 6000, > + period); > + reg |= TIMING_TRP(OFFSET(val, 1)) | TIMING_TRP_RESP(OFFSET(val, 1)); > + > + reg |= TIMING_TWB(OFFSET(DIV_ROUND_UP(timings->tWB_max, period), 1)); > + reg |= TIMING_TWHR(OFFSET(DIV_ROUND_UP(timings->tWHR_min, period), 1)); > + reg |= TIMING_TWH(OFFSET(DIV_ROUND_UP(timings->tWH_min, period), 1)); > + reg |= TIMING_TWP(OFFSET(DIV_ROUND_UP(timings->tWP_min, period), 1)); > + reg |= TIMING_TRH(OFFSET(DIV_ROUND_UP(timings->tREH_min, period), 1)); > + > + writel_relaxed(reg, ctrl->regs + TIMING_1); > + > + val = DIV_ROUND_UP(timings->tADL_min, period); > + reg = TIMING_TADL(OFFSET(val, 3)); > + > + writel_relaxed(reg, ctrl->regs + TIMING_2); > +} > + > +static int tegra_nand_setup_data_interface(struct mtd_info *mtd, int csline, > + const struct nand_data_interface *conf) > +{ > + struct nand_chip *chip = mtd_to_nand(mtd); > + struct tegra_nand_controller *ctrl = to_tegra_ctrl(chip->controller); > + const struct nand_sdr_timings *timings; > + > + timings = nand_get_sdr_timings(conf); > + if (IS_ERR(timings)) > + return PTR_ERR(timings); > + > + if (csline == NAND_DATA_IFACE_CHECK_ONLY) > + return 0; > + > + tegra_nand_setup_timing(ctrl, timings); > + > + return 0; > +} > + > + > +const int rs_strength_bootable[] = { 4 }; > +const int rs_strength[] = { 4, 6, 8 }; > +const int bch_strength_bootable[] = { 8, 16 }; > +const int bch_strength[] = { 4, 8, 14, 16 }; These const's shall be 'static'. > + > +static int tegra_nand_get_strength(struct nand_chip *chip, const int *strength, > + int strength_len, int oobsize) > +{ > + bool maximize = chip->ecc.options & NAND_ECC_MAXIMIZE; > + int i; > + > + /* > + * Loop through available strengths. Backwards in case we try to > + * maximize the BCH strength. > + */ > + for (i = 0; i < strength_len; i++) { > + int strength_sel, bytes_per_step, bytes_per_page; > + > + if (maximize) { > + strength_sel = strength[strength_len - i - 1]; > + } else { > + strength_sel = strength[i]; > + > + if (strength_sel < chip->ecc_strength_ds) > + continue; > + } > + > + bytes_per_step = DIV_ROUND_UP(BITS_PER_STEP_BCH * strength_sel, > + BITS_PER_BYTE); > + bytes_per_page = round_up(bytes_per_step * chip->ecc.steps, 4); > + > + /* Check whether strength fits OOB */ > + if (bytes_per_page < (oobsize - SKIP_SPARE_BYTES)) > + return strength_sel; > + } > + > + return -EINVAL; > +} > + > +static int tegra_nand_select_strength(struct nand_chip *chip, int oobsize) > +{ > + const int *strength; > + int strength_len; > + > + switch (chip->ecc.algo) { > + case NAND_ECC_RS: > + if (chip->options & NAND_IS_BOOT_MEDIUM) { > + strength = rs_strength_bootable; > + strength_len = ARRAY_SIZE(rs_strength_bootable); > + } else { > + strength = rs_strength; > + strength_len = ARRAY_SIZE(rs_strength); > + } > + break; > + case NAND_ECC_BCH: > + if (chip->options & NAND_IS_BOOT_MEDIUM) { > + strength = bch_strength_bootable; > + strength_len = ARRAY_SIZE(bch_strength_bootable); > + } else { > + strength = bch_strength; > + strength_len = ARRAY_SIZE(bch_strength); > + } > + break; > + default: > + return -EINVAL; > + } > + > + return tegra_nand_get_strength(chip, strength, strength_len, oobsize); > +} > + > +static int tegra_nand_chips_init(struct device *dev, > + struct tegra_nand_controller *ctrl) > +{ > + struct device_node *np = dev->of_node; > + struct device_node *np_nand; > + int nchips = of_get_child_count(np); > + struct tegra_nand_chip *nand; > + struct mtd_info *mtd; > + struct nand_chip *chip; > + unsigned long config, bch_config = 0; > + int bits_per_step; > + int ret; > + > + if (nchips != 1) { > + dev_err(dev, "Currently only one NAND chip supported\n"); > + return -EINVAL; > + } > + > + np_nand = of_get_next_child(np, NULL); > + > + nand = devm_kzalloc(dev, sizeof(*nand), GFP_KERNEL); > + if (!nand) > + return -ENOMEM; > + > + nand->wp_gpio = devm_gpiod_get_optional(dev, "wp", GPIOD_OUT_LOW); > + > + if (IS_ERR(nand->wp_gpio)) { > + ret = PTR_ERR(nand->wp_gpio); > + dev_err(dev, "Failed to request WP GPIO: %d\n", ret); > + return ret; > + } > + > + chip = &nand->chip; > + chip->controller = &ctrl->controller; > + > + mtd = nand_to_mtd(chip); > + > + mtd->dev.parent = dev; > + if (!mtd->name) > + mtd->name = "tegra_nand"; > + mtd->owner = THIS_MODULE; > + > + nand_set_flash_node(chip, np_nand); > + > + chip->options = NAND_NO_SUBPAGE_WRITE | NAND_USE_BOUNCE_BUFFER; > + chip->exec_op = tegra_nand_exec_op; > + chip->select_chip = tegra_nand_select_chip; > + chip->setup_data_interface = tegra_nand_setup_data_interface; > + > + ret = nand_scan_ident(mtd, 1, NULL); > + if (ret) > + return ret; > + > + if (chip->bbt_options & NAND_BBT_USE_FLASH) > + chip->bbt_options |= NAND_BBT_NO_OOB; > + > + chip->ecc.mode = NAND_ECC_HW; > + chip->ecc.size = 512; > + chip->ecc.steps = mtd->writesize / chip->ecc.size; > + if (chip->ecc_step_ds != 512) { > + dev_err(dev, "Unsupported step size %d\n", chip->ecc_step_ds); > + return -EINVAL; > + } > + > + chip->ecc.read_page = tegra_nand_read_page_hwecc; > + chip->ecc.write_page = tegra_nand_write_page_hwecc; > + > + config = readl_relaxed(ctrl->regs + CFG); > + config |= CFG_PIPE_EN | CFG_SKIP_SPARE | CFG_SKIP_SPARE_SIZE_4; > + > + if (chip->options & NAND_BUSWIDTH_16) > + config |= CFG_BUS_WIDTH_16; > + > + if (chip->ecc.algo == NAND_ECC_UNKNOWN) { > + if (mtd->writesize < 2048) > + chip->ecc.algo = NAND_ECC_RS; > + else > + chip->ecc.algo = NAND_ECC_BCH; > + } > + > + if (chip->ecc.algo == NAND_ECC_BCH && mtd->writesize < 2048) { > + dev_err(dev, "BCH supportes 2K or 4K page size only\n"); > + return -EINVAL; > + } > + > + if (!chip->ecc.strength) { > + ret = tegra_nand_select_strength(chip, mtd->oobsize); > + if (ret < 0) { > + dev_err(dev, "No valid strenght found, minimum %d\n", > + chip->ecc_strength_ds); > + return ret; > + } > + > + chip->ecc.strength = ret; > + } > + > + switch (chip->ecc.algo) { > + case NAND_ECC_RS: > + bits_per_step = BITS_PER_STEP_RS * chip->ecc.strength; > + mtd_set_ooblayout(mtd, &tegra_nand_oob_rs_ops); > + switch (chip->ecc.strength) { > + case 4: > + config |= CFG_ECC_SEL | CFG_TVAL_4; > + break; > + case 6: > + config |= CFG_ECC_SEL | CFG_TVAL_6; > + break; > + case 8: > + config |= CFG_ECC_SEL | CFG_TVAL_8; > + break; > + default: > + dev_err(dev, "ECC strength %d not supported\n", > + chip->ecc.strength); > + return -EINVAL; > + } > + break; > + case NAND_ECC_BCH: > + bits_per_step = BITS_PER_STEP_BCH * chip->ecc.strength; > + mtd_set_ooblayout(mtd, &tegra_nand_oob_bch_ops); > + switch (chip->ecc.strength) { > + case 4: > + bch_config = BCH_TVAL_4; > + break; > + case 8: > + bch_config = BCH_TVAL_8; > + break; > + case 14: > + bch_config = BCH_TVAL_14; > + break; > + case 16: > + bch_config = BCH_TVAL_16; > + break; > + default: > + dev_err(dev, "ECC strength %d not supported\n", > + chip->ecc.strength); > + return -EINVAL; > + } > + break; > + default: > + dev_err(dev, "ECC algorithm not supported\n"); > + return -EINVAL; > + } > + > + dev_info(dev, "Using %s with strength %d per 512 byte step\n", > + chip->ecc.algo == NAND_ECC_BCH ? "BCH" : "RS", > + chip->ecc.strength); > + > + chip->ecc.bytes = DIV_ROUND_UP(bits_per_step, BITS_PER_BYTE); > + > + switch (mtd->writesize) { > + case 256: > + config |= CFG_PS_256; > + break; > + case 512: > + config |= CFG_PS_512; > + break; > + case 1024: > + config |= CFG_PS_1024; > + break; > + case 2048: > + config |= CFG_PS_2048; > + break; > + case 4096: > + config |= CFG_PS_4096; > + break; > + default: > + dev_err(dev, "Unsupported writesize %d\n", mtd->writesize); > + return -ENODEV; > + } > + > + writel_relaxed(config, ctrl->regs + CFG); > + writel_relaxed(bch_config, ctrl->regs + BCH_CONFIG); > + > + ret = nand_scan_tail(mtd); > + if (ret) > + return ret; > + > + mtd_ooblayout_free(mtd, 0, &nand->tag); > + > + config |= CFG_TAG_BYTE_SIZE(nand->tag.length - 1); > + writel_relaxed(config, ctrl->regs + CFG); > + > + ret = mtd_device_register(mtd, NULL, 0); > + if (ret) { > + dev_err(dev, "Failed to register mtd device: %d\n", ret); > + nand_cleanup(chip); > + return ret; > + } > + > + ctrl->chip = chip; > + > + return 0; > +} > + > +static int tegra_nand_probe(struct platform_device *pdev) > +{ > + struct reset_control *rst; > + struct tegra_nand_controller *ctrl; > + struct resource *res; > + unsigned long reg; > + int irq, err = 0; > + > + ctrl = devm_kzalloc(&pdev->dev, sizeof(*ctrl), GFP_KERNEL); > + if (!ctrl) > + return -ENOMEM; > + > + ctrl->dev = &pdev->dev; > + nand_hw_control_init(&ctrl->controller); > + > + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); > + ctrl->regs = devm_ioremap_resource(&pdev->dev, res); > + if (IS_ERR(ctrl->regs)) > + return PTR_ERR(ctrl->regs); > + > + rst = devm_reset_control_get(&pdev->dev, "nand"); > + if (IS_ERR(rst)) > + return PTR_ERR(rst); > + > + ctrl->clk = devm_clk_get(&pdev->dev, "nand"); > + if (IS_ERR(ctrl->clk)) > + return PTR_ERR(ctrl->clk); > + > + err = clk_prepare_enable(ctrl->clk); > + if (err) > + return err; > + > + err = reset_control_reset(rst); > + if (err) > + goto err_disable_clk; > + > + reg = HWSTATUS_RDSTATUS_MASK(1) | HWSTATUS_RDSTATUS_VALUE(0) | > + HWSTATUS_RBSY_MASK(NAND_STATUS_READY) | > + HWSTATUS_RBSY_VALUE(NAND_STATUS_READY); > + writel_relaxed(NAND_CMD_STATUS, ctrl->regs + HWSTATUS_CMD); > + writel_relaxed(reg, ctrl->regs + HWSTATUS_MASK); > + > + init_completion(&ctrl->command_complete); > + init_completion(&ctrl->dma_complete); > + > + /* clear interrupts */ > + reg = readl_relaxed(ctrl->regs + ISR); > + writel_relaxed(reg, ctrl->regs + ISR); > + > + irq = platform_get_irq(pdev, 0); > + err = devm_request_irq(&pdev->dev, irq, tegra_nand_irq, 0, > + dev_name(&pdev->dev), ctrl); > + if (err) > + goto err_disable_clk; > + > + writel_relaxed(DMA_CTRL_IS_DONE, ctrl->regs + DMA_CTRL); > + > + /* enable interrupts */ > + reg = IER_UND | IER_OVR | IER_CMD_DONE | IER_GIE; > + writel_relaxed(reg, ctrl->regs + IER); > + > + /* reset config */ > + writel_relaxed(0, ctrl->regs + CFG); > + > + err = tegra_nand_chips_init(ctrl->dev, ctrl); > + if (err) > + goto err_disable_clk; > + > + platform_set_drvdata(pdev, ctrl); > + > + return 0; > + > +err_disable_clk: > + clk_disable_unprepare(ctrl->clk); > + return err; > +} > + > +static int tegra_nand_remove(struct platform_device *pdev) > +{ > + struct tegra_nand_controller *ctrl = platform_get_drvdata(pdev); > + > + nand_release(nand_to_mtd(ctrl->chip)); > + > + clk_disable_unprepare(ctrl->clk); > + > + return 0; > +} > + > +static const struct of_device_id tegra_nand_of_match[] = { > + { .compatible = "nvidia,tegra20-nand" }, > + { /* sentinel */ } > +}; > + > +static struct platform_driver tegra_nand_driver = { > + .driver = { > + .name = "tegra-nand", > + .of_match_table = tegra_nand_of_match, > + }, > + .probe = tegra_nand_probe, > + .remove = tegra_nand_remove, > +}; > +module_platform_driver(tegra_nand_driver); > + > +MODULE_DESCRIPTION("NVIDIA Tegra NAND driver"); > +MODULE_AUTHOR("Thierry Reding <thierry.reding@xxxxxxxxxx>"); > +MODULE_AUTHOR("Lucas Stach <dev@xxxxxxxxxx>"); > +MODULE_AUTHOR("Stefan Agner <stefan@xxxxxxxx>"); > +MODULE_LICENSE("GPL v2"); > +MODULE_DEVICE_TABLE(of, tegra_nand_of_match); > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html