On 3/7/25 7:13 AM, Troy Mitchell wrote:
This patch introduces basic I2C support for the SpacemiT K1 SoC,
utilizing interrupts for transfers.
The driver has been tested using i2c-tools on a Bananapi-F3 board,
and basic I2C read/write operations have been confirmed to work.
Signed-off-by: Troy Mitchell <troymitchell988@xxxxxxxxx>
I have a bunch of really small suggestions. Please consider
them, but whatever you choose to do this looks good to me.
Reviewed-by: Alex Elder <elder@xxxxxxxxxxxx>
---
drivers/i2c/busses/Kconfig | 17 ++
drivers/i2c/busses/Makefile | 1 +
drivers/i2c/busses/i2c-k1.c | 601 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 619 insertions(+)
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index fc438f4457713d5559d163840a7b11e8cdbb8f58..12d0e99566d8625aa374279956b71a4034ded4ac 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -783,6 +783,23 @@ config I2C_JZ4780
If you don't know what to do here, say N.
+config I2C_K1
+ tristate "Spacemit K1 I2C adapter"
+ depends on ARCH_SPACEMIT || COMPILE_TEST
+ depends on OF
+ help
+ This option enables support for the I2C interface on the Spacemit K1
+ platform.
+
+ If you enable this configuration, the kernel will include support for
+ the I2C adapter specific to the Spacemit K1 platform. This driver can
+ be used to manage I2C bus transactions, which are necessary for
+ interfacing with I2C peripherals such as sensors, EEPROMs, and other
+ devices.
Does SpacemiT prefer to have the T at the end of their name
capitalized?
+
+ This driver can also be built as a module. If so, the
+ module will be called `i2c-k1`.
+
config I2C_KEBA
tristate "KEBA I2C controller support"
depends on HAS_IOMEM
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 1c2a4510abe44a689dfe67d2d64cf0cf3434f510..c1252e2b779e2e47492d66179b442f2202ec0416 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -74,6 +74,7 @@ obj-$(CONFIG_I2C_IMX) += i2c-imx.o
obj-$(CONFIG_I2C_IMX_LPI2C) += i2c-imx-lpi2c.o
obj-$(CONFIG_I2C_IOP3XX) += i2c-iop3xx.o
obj-$(CONFIG_I2C_JZ4780) += i2c-jz4780.o
+obj-$(CONFIG_I2C_K1) += i2c-k1.o
obj-$(CONFIG_I2C_KEBA) += i2c-keba.o
obj-$(CONFIG_I2C_KEMPLD) += i2c-kempld.o
obj-$(CONFIG_I2C_LPC2K) += i2c-lpc2k.o
diff --git a/drivers/i2c/busses/i2c-k1.c b/drivers/i2c/busses/i2c-k1.c
new file mode 100644
index 0000000000000000000000000000000000000000..1ef98a303fb14ce10d283225ce0617a0b9f405f7
--- /dev/null
+++ b/drivers/i2c/busses/i2c-k1.c
@@ -0,0 +1,601 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Troy Mitchell <troymitchell988@xxxxxxxxx>
Maybe update your copyright date(s) to include this year before
your final version of the patch.
+ */
+
+ #include <linux/clk.h>
+ #include <linux/i2c.h>
+ #include <linux/iopoll.h>
+ #include <linux/module.h>
+ #include <linux/of_address.h>
+ #include <linux/platform_device.h>
+
+/* spacemit i2c registers */
+#define SPACEMIT_ICR 0x0 /* Control Register */
s/Register/register/
+#define SPACEMIT_ISR 0x4 /* Status Register */
s/Register/register/
+#define SPACEMIT_IDBR 0xc /* Data Buffer Register */
s/Buffer Re/buffer re/
+#define SPACEMIT_IBMR 0x1c /* Bus monitor register */
+
+/* SPACEMIT_ICR register fields */
+#define SPACEMIT_CR_START BIT(0) /* start bit */
+#define SPACEMIT_CR_STOP BIT(1) /* stop bit */
+#define SPACEMIT_CR_ACKNAK BIT(2) /* send ACK(0) or NAK(1) */
+#define SPACEMIT_CR_TB BIT(3) /* transfer byte bit */
+/* Bits 4-7 are reserved */
+#define SPACEMIT_CR_MODE_FAST BIT(8) /* bus mode (master operation) */
+/* Bit 9 is reserved */
+#define SPACEMIT_CR_UR BIT(10) /* unit reset */
+/* Bits 11-12 are reserved */
+#define SPACEMIT_CR_SCLE BIT(13) /* master clock enable */
+#define SPACEMIT_CR_IUE BIT(14) /* unit enable */
+/* Bits 15-17 are reserved */
+#define SPACEMIT_CR_ALDIE BIT(18) /* enable arbitration interrupt */
+#define SPACEMIT_CR_DTEIE BIT(19) /* enable tx interrupts */
+#define SPACEMIT_CR_DRFIE BIT(20) /* enable rx interrupts */
+#define SPACEMIT_CR_GCD BIT(21) /* general call disable */
+#define SPACEMIT_CR_BEIE BIT(22) /* enable bus error ints */
+/* Bits 23-24 are reserved */
+#define SPACEMIT_CR_MSDIE BIT(25) /* master STOP detected int enable */
+#define SPACEMIT_CR_MSDE BIT(26) /* master STOP detected enable */
+#define SPACEMIT_CR_TXDONEIE BIT(27) /* transaction done int enable */
+#define SPACEMIT_CR_TXEIE BIT(28) /* transmit FIFO empty int enable */
+#define SPACEMIT_CR_RXHFIE BIT(29) /* receive FIFO half-full int enable */
+#define SPACEMIT_CR_RXFIE BIT(30) /* receive FIFO full int enable */
+#define SPACEMIT_CR_RXOVIE BIT(31) /* receive FIFO overrun int enable */
+
+#define SPACEMIT_I2C_INT_CTRL_MASK (SPACEMIT_CR_ALDIE | SPACEMIT_CR_DTEIE | \
+ SPACEMIT_CR_DRFIE | SPACEMIT_CR_BEIE | \
+ SPACEMIT_CR_TXDONEIE | SPACEMIT_CR_TXEIE | \
+ SPACEMIT_CR_RXHFIE | SPACEMIT_CR_RXFIE | \
+ SPACEMIT_CR_RXOVIE | SPACEMIT_CR_MSDIE)
+
+/* SPACEMIT_ISR register fields */
+/* Bits 0-13 are reserved */
+#define SPACEMIT_SR_ACKNAK BIT(14) /* ACK/NACK status */
+#define SPACEMIT_SR_UB BIT(15) /* unit busy */
+#define SPACEMIT_SR_IBB BIT(16) /* i2c bus busy */
+#define SPACEMIT_SR_EBB BIT(17) /* early bus busy */
+#define SPACEMIT_SR_ALD BIT(18) /* arbitration loss detected */
+#define SPACEMIT_SR_ITE BIT(19) /* tx buffer empty */
+#define SPACEMIT_SR_IRF BIT(20) /* rx buffer full */
+#define SPACEMIT_SR_GCAD BIT(21) /* general call address detected */
+#define SPACEMIT_SR_BED BIT(22) /* bus error no ACK/NAK */
+#define SPACEMIT_SR_SAD BIT(23) /* slave address detected */
+#define SPACEMIT_SR_SSD BIT(24) /* slave stop detected */
+/* Bit 25 is reserved */
+#define SPACEMIT_SR_MSD BIT(26) /* master stop detected */
+#define SPACEMIT_SR_TXDONE BIT(27) /* transaction done */
+#define SPACEMIT_SR_TXE BIT(28) /* tx FIFO empty */
+#define SPACEMIT_SR_RXHF BIT(29) /* rx FIFO half-full */
+#define SPACEMIT_SR_RXF BIT(30) /* rx FIFO full */
+#define SPACEMIT_SR_RXOV BIT(31) /* RX FIFO overrun */
s/RX FIFO/rx FIFO/
Or preferably, use "TX" and "RX" an all the comments (and anywhere
else you use "tx" and "rx" in the file).
+
+#define SPACEMIT_I2C_INT_STATUS_MASK (SPACEMIT_SR_RXOV | SPACEMIT_SR_RXF | SPACEMIT_SR_RXHF | \
+ SPACEMIT_SR_TXE | SPACEMIT_SR_TXDONE | SPACEMIT_SR_MSD | \
+ SPACEMIT_SR_SSD | SPACEMIT_SR_SAD | SPACEMIT_SR_BED | \
+ SPACEMIT_SR_GCAD | SPACEMIT_SR_IRF | SPACEMIT_SR_ITE | \
+ SPACEMIT_SR_ALD)
+
+/* SPACEMIT_IBMR register fields */
+#define SPACEMIT_BMR_SDA BIT(0) /* SDA line level */
+#define SPACEMIT_BMR_SCL BIT(1) /* SCL line level */
+
+/* i2c bus recover timeout: us */
+#define SPACEMIT_I2C_BUS_BUSY_TIMEOUT 100000
Align the 100000 above with the frequency values below.
+
+#define SPACEMIT_SR_ERR (SPACEMIT_SR_BED | SPACEMIT_SR_RXOV | SPACEMIT_SR_ALD)
+
Maybe it's obvious but you could comment that the unit
for these values is Hz.
+#define SPACEMIT_I2C_MAX_STANDARD_MODE_FREQ 100000
+#define SPACEMIT_I2C_MAX_FAST_MODE_FREQ 400000
+
+enum spacemit_i2c_state {
+ STATE_IDLE,
+ STATE_START,
+ STATE_READ,
+ STATE_WRITE,
+};
+
+/* i2c-spacemit driver's main struct */
+struct spacemit_i2c_dev {
+ struct device *dev;
+ struct i2c_adapter adapt;
+
+ /* hardware resources */
+ void __iomem *base;
+ int irq;
+ u32 clock_freq;
+
+ struct i2c_msg *msgs;
+ int msg_num;
You'll never have a negative number of messages. (I see
it's assigned an int value, but my statement is still true.)
So this can be unsigned (u32).
+
+ /* index of the current message being processed */
+ int msg_idx;
msg_idx can also be unsigned.
+ u8 *msg_buf;
+ /* the number of unprocessed bytes remaining in each message */
s/each/the current/
+ size_t unprocessed;
Why is unprocessed a size_t? It's OK, but msg_idx is a
simple (unsigned) int.
+
+ enum spacemit_i2c_state state;
+ bool read;
+ struct completion complete;
+ u32 status;
+};
+
+static void spacemit_i2c_enable(struct spacemit_i2c_dev *i2c)
+{
+ u32 val;
+
+ val = readl(i2c->base + SPACEMIT_ICR);
+ val |= SPACEMIT_CR_IUE;
+ writel(val, i2c->base + SPACEMIT_ICR);
+}
+
+static void spacemit_i2c_disable(struct spacemit_i2c_dev *i2c)
+{
+ u32 val;
+
+ val = readl(i2c->base + SPACEMIT_ICR);
+ val &= ~SPACEMIT_CR_IUE;
+ writel(val, i2c->base + SPACEMIT_ICR);
+}
+
+static void spacemit_i2c_reset(struct spacemit_i2c_dev *i2c)
+{
+ writel(SPACEMIT_CR_UR, i2c->base + SPACEMIT_ICR);
+ udelay(5);
+ writel(0, i2c->base + SPACEMIT_ICR);
+}
+
+static int spacemit_i2c_handle_err(struct spacemit_i2c_dev *i2c)
+{
+ dev_dbg(i2c->dev, "i2c error status: 0x%08x\n", i2c->status);
+
+ if (i2c->status & (SPACEMIT_SR_BED | SPACEMIT_SR_ALD)) {
+ spacemit_i2c_reset(i2c);
+ return -EAGAIN;
+ }
+
+ return i2c->status & SPACEMIT_SR_ACKNAK ? -ENXIO : -EIO;
+}
+
+static void spacemit_i2c_conditionally_reset_bus(struct spacemit_i2c_dev *i2c)
+{
+ u32 status;
+
+ /* if bus is locked, reset unit. 0: locked */
+ status = readl(i2c->base + SPACEMIT_IBMR);
+ if ((status & SPACEMIT_BMR_SDA) && (status & SPACEMIT_BMR_SCL))
+ return;
+
+ spacemit_i2c_reset(i2c);
+ usleep_range(10, 20);
+
+ /* check scl status again */
+ status = readl(i2c->base + SPACEMIT_IBMR);
+ if (!(status & SPACEMIT_BMR_SCL))
+ dev_warn_ratelimited(i2c->dev, "unit reset failed\n");
+}
+
I think this is waiting for the bus to *not* be busy.
So spacemit_i2c_wait_bus_free() (or maybe _idle()) would
make more sense.
+static int spacemit_i2c_wait_bus_busy(struct spacemit_i2c_dev *i2c)
+{
+ int ret;
+ u32 val;
+
+ val = readl(i2c->base + SPACEMIT_ISR);
+ if (!(val & (SPACEMIT_SR_UB | SPACEMIT_SR_IBB)))
+ return 0;
+
+ ret = readl_poll_timeout(i2c->base + SPACEMIT_ISR,
+ val, !(val & (SPACEMIT_SR_UB | SPACEMIT_SR_IBB)),
+ 1500, SPACEMIT_I2C_BUS_BUSY_TIMEOUT);
+ if (ret)
+ spacemit_i2c_reset(i2c);
+
+ return ret;
+}
+
+static void spacemit_i2c_check_bus_release(struct spacemit_i2c_dev *i2c)
+{
+ /* in case bus is not released after transfer completes */
+ if (readl(i2c->base + SPACEMIT_ISR) & SPACEMIT_SR_EBB) {
+ spacemit_i2c_conditionally_reset_bus(i2c);
+ usleep_range(90, 150);
+ }
+}
+
+static void spacemit_i2c_init(struct spacemit_i2c_dev *i2c)
+{
+ u32 val;
+
+ /*
+ * Unmask interrupt bits for all xfer mode:
+ * bus error, arbitration loss detected.
+ * For transaction complete signal, we use master stop
+ * interrupt, so we don't need to unmask SPACEMIT_CR_TXDONEIE.
+ */
+ val = SPACEMIT_CR_BEIE | SPACEMIT_CR_ALDIE;
+
+ /*
+ * Unmask interrupt bits for interrupt xfer mode:
+ * DBR rx full.
+ * For tx empty interrupt SPACEMIT_CR_DTEIE, we only
+ * need to enable when trigger byte transfer to start
+ * data sending.
+ */
+ val |= SPACEMIT_CR_DRFIE;
+
+ if (i2c->clock_freq == SPACEMIT_I2C_MAX_FAST_MODE_FREQ)
+ val |= SPACEMIT_CR_MODE_FAST;
+
+ /* disable response to general call */
+ val |= SPACEMIT_CR_GCD;
+
+ /* enable SCL clock output */
+ val |= SPACEMIT_CR_SCLE;
+
+ /* enable master stop detected */
+ val |= SPACEMIT_CR_MSDE | SPACEMIT_CR_MSDIE;
+
+ writel(val, i2c->base + SPACEMIT_ICR);
+}
+
+static inline void
s/inline //
+spacemit_i2c_clear_int_status(struct spacemit_i2c_dev *i2c, u32 mask)
+{
+ writel(mask & SPACEMIT_I2C_INT_STATUS_MASK, i2c->base + SPACEMIT_ISR);
+}
+
+static void spacemit_i2c_start(struct spacemit_i2c_dev *i2c)
+{
+ u32 slave_addr_rw, val;
+ struct i2c_msg *cur_msg = i2c->msgs + i2c->msg_idx;
+
+ i2c->read = !!(cur_msg->flags & I2C_M_RD);
+
+ i2c->state = STATE_START;
+
+ slave_addr_rw = (cur_msg->addr & 0x7f) << 1;
+ if (cur_msg->flags & I2C_M_RD)
+ slave_addr_rw |= 1;
+
+ writel(slave_addr_rw, i2c->base + SPACEMIT_IDBR);
+
+ /* send start pulse */
+ val = readl(i2c->base + SPACEMIT_ICR);
+ val &= ~SPACEMIT_CR_STOP;
+ val |= SPACEMIT_CR_START | SPACEMIT_CR_TB | SPACEMIT_CR_DTEIE;
+ writel(val, i2c->base + SPACEMIT_ICR);
+}
+
+static void spacemit_i2c_stop(struct spacemit_i2c_dev *i2c)
+{
+ u32 val;
+
+ val = readl(i2c->base + SPACEMIT_ICR);
+ val |= SPACEMIT_CR_STOP | SPACEMIT_CR_ALDIE | SPACEMIT_CR_TB;
+
+ if (i2c->read)
+ val |= SPACEMIT_CR_ACKNAK;
+
+ writel(val, i2c->base + SPACEMIT_ICR);
+}
+
+static int spacemit_i2c_xfer_msg(struct spacemit_i2c_dev *i2c)
+{
+ unsigned long time_left;
+
+ for (i2c->msg_idx = 0; i2c->msg_idx < i2c->msg_num; i2c->msg_idx++) {
+ i2c->msg_buf = (i2c->msgs + i2c->msg_idx)->buf;
+ i2c->status = 0;
+ i2c->unprocessed = (i2c->msgs + i2c->msg_idx)->len;
I think this might be more understandable. The array syntax
shows it's really an array; and the local variable simplifies
the right-hand sides.
struct i2c_msg *msg = &i2c->msgs[i2c->msg_idx];
i2c->msg_buf = msg->buf;
i2c->unprocessed = msg->len;
i2c->status = 0;
+
+ reinit_completion(&i2c->complete);
+
+ spacemit_i2c_start(i2c);
+
+ time_left = wait_for_completion_timeout(&i2c->complete,
+ i2c->adapt.timeout);
+ if (time_left == 0) {
if (!time_left) {
+ dev_err(i2c->dev, "msg completion timeout\n");
+ spacemit_i2c_conditionally_reset_bus(i2c);
+ spacemit_i2c_reset(i2c);
+ return -ETIMEDOUT;
+ }
+
+ if (i2c->status & SPACEMIT_SR_ERR)
+ return spacemit_i2c_handle_err(i2c);
+ }
+
+ return 0;
+}
. . .
+static void spacemit_i2c_calc_timeout(struct spacemit_i2c_dev *i2c)
+{
+ unsigned long timeout;
+ int idx = 0, cnt = 0;
+
+ while (idx < i2c->msg_num) {
+ cnt += (i2c->msgs + idx)->len + 1;
+ idx++;
+ }
+
+ /*
+ * multiply by 9 because each byte in I2C transmission requires
+ * 9 clock cycles: 8 bits of data plus 1 ACK/NACK bit.
+ */
+ timeout = cnt * 9 * USEC_PER_SEC / i2c->clock_freq;
+
+ i2c->adapt.timeout = usecs_to_jiffies(timeout + USEC_PER_SEC / 2) / i2c->msg_num;
I think the half second pad on your timeout will essentially
always dominate the timeout period. If you transfer a
maximally-sized message at 100000 Hz it'll take almost
6 seconds. But in practice I'm sure transfers are under
32 bytes (maybe 256?). At 256 bytes you're looking at
23 milliseconds (plus 500000) at 100 KHz.
I looked around and the timeouts used for I2C adapters are
all over the map. 50 seconds, 1 second, 100 milliseconds,
and so on, so I guess what you're doing is fine.
That said, it might not be very important to be as precise
as you are here.
+}
+
. . .
+static const struct i2c_algorithm spacemit_i2c_algo = {
+ .xfer = spacemit_i2c_xfer,
+ .functionality = spacemit_i2c_func,
+};
+
+static int spacemit_i2c_probe(struct platform_device *pdev)
+{
+ struct clk *clk;
+ struct device *dev = &pdev->dev;
+ struct device_node *of_node = pdev->dev.of_node;
+ struct spacemit_i2c_dev *i2c;
+ int ret;
+
+ i2c = devm_kzalloc(dev, sizeof(*i2c), GFP_KERNEL);
+ if (!i2c)
+ return -ENOMEM;
+
+ ret = of_property_read_u32(of_node, "clock-frequency", &i2c->clock_freq);
+ if (ret)
+ return dev_err_probe(dev, ret, "failed to read clock-frequency property");
Your binding doesn't say that the "clock-frequency" property is
required. If it's not found, you should default to 400000 Hz.
There should be no error here.
+
+ /* For now, this driver doesn't support high-speed. */
The clock frequency is unsigned, so:
if (!i2c->clock_freq || ...) {
+ if (i2c->clock_freq < 1 || i2c->clock_freq > SPACEMIT_I2C_MAX_FAST_MODE_FREQ) {
+ dev_warn(dev, "unsupport clock frequency: %d, default: %d",
dev_warn(dev, "unsupported clock frequency %u; using %u\n",
+ i2c->clock_freq, SPACEMIT_I2C_MAX_FAST_MODE_FREQ);
+ i2c->clock_freq = SPACEMIT_I2C_MAX_FAST_MODE_FREQ;
+ } else if (i2c->clock_freq < SPACEMIT_I2C_MAX_STANDARD_MODE_FREQ) {
I would issue the same warning message here.
+ i2c->clock_freq = SPACEMIT_I2C_MAX_STANDARD_MODE_FREQ;
+ }
+
+ i2c->dev = &pdev->dev;
+
+ i2c->base = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(i2c->base))
+ return dev_err_probe(dev, PTR_ERR(i2c->base), "failed to do ioremap");
+
+ i2c->irq = platform_get_irq(pdev, 0);
+ if (i2c->irq < 0)
+ return dev_err_probe(dev, i2c->irq, "failed to get irq resource");
+
+ ret = devm_request_irq(i2c->dev, i2c->irq, spacemit_i2c_irq_handler,
+ IRQF_NO_SUSPEND | IRQF_ONESHOT, dev_name(i2c->dev), i2c);
+ if (ret)
+ return dev_err_probe(dev, ret, "failed to request irq");
+
+ clk = devm_clk_get_enabled(dev, "func");
+ if (IS_ERR(clk))
+ return dev_err_probe(dev, PTR_ERR(clk), "failed to enable func clock");
+
+ clk = devm_clk_get_enabled(dev, "bus");
+ if (IS_ERR(clk))
+ return dev_err_probe(dev, PTR_ERR(clk), "failed to enable bus clock");
+
+ spacemit_i2c_reset(i2c);
+
+ i2c_set_adapdata(&i2c->adapt, i2c);
+ i2c->adapt.owner = THIS_MODULE;
+ i2c->adapt.algo = &spacemit_i2c_algo;
+ i2c->adapt.dev.parent = i2c->dev;
+ i2c->adapt.nr = pdev->id;
+
+ i2c->adapt.dev.of_node = of_node;
+ i2c->adapt.algo_data = i2c;
I don't think you ever use i2c->adapt.algo_data. All you
need is the i2c pointer you set with i2c_set_adapdata().
That's it!
-Alex
+
+ strscpy(i2c->adapt.name, "spacemit-i2c-adapter", sizeof(i2c->adapt.name));
+
+ init_completion(&i2c->complete);
+
+ platform_set_drvdata(pdev, i2c);
+
+ ret = i2c_add_numbered_adapter(&i2c->adapt);
+ if (ret)
+ return dev_err_probe(&pdev->dev, ret, "failed to add i2c adapter");
+
+ return 0;
+}
+
+static void spacemit_i2c_remove(struct platform_device *pdev)
+{
+ struct spacemit_i2c_dev *i2c = platform_get_drvdata(pdev);
+
+ i2c_del_adapter(&i2c->adapt);
+}
+
+static const struct of_device_id spacemit_i2c_of_match[] = {
+ { .compatible = "spacemit,k1-i2c", },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, spacemit_i2c_of_match);
+
+static struct platform_driver spacemit_i2c_driver = {
+ .probe = spacemit_i2c_probe,
+ .remove = spacemit_i2c_remove,
+ .driver = {
+ .name = "i2c-k1",
+ .of_match_table = spacemit_i2c_of_match,
+ },
+};
+module_platform_driver(spacemit_i2c_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("I2C bus driver for SpacemiT K1 SoC");
