Allwinner NAND controllers can make use of DMA to enhance the I/O
throughput thanks to ECC pipelining. DMA handling with A33 NAND IP
is a bit different than with the older SoCs, hence the introduction of
a new compatible to handle:
* the differences between register offsets,
* the burst length change from 4 to minimum 8,
* drive SRAM accesses through the AHB bus instead of the MBUS.
Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
---
Changes in v2:
* Enumerate the SoCs already supported (A10, A10s, A13 and A20)
instead of using the inaccurate acronym 'A10+'.
* s/p.12 of the user manual/p.12 of the *NFC* user manual/
* s/sun8i/A33/
drivers/mtd/nand/raw/sunxi_nand.c | 38 +++++++++++++++++++++++++++++--
1 file changed, 36 insertions(+), 2 deletions(-)
diff --git a/drivers/mtd/nand/raw/sunxi_nand.c b/drivers/mtd/nand/raw/sunxi_nand.c
index 7b824c245083..18fa30175d67 100644
--- a/drivers/mtd/nand/raw/sunxi_nand.c
+++ b/drivers/mtd/nand/raw/sunxi_nand.c
@@ -43,6 +43,7 @@
#define NFC_REG_RCMD_SET 0x0028
#define NFC_REG_WCMD_SET 0x002C
#define NFC_REG_A10_IO_DATA 0x0030
+#define NFC_REG_A33_IO_DATA 0x0300
#define NFC_REG_ECC_CTL 0x0034
#define NFC_REG_ECC_ST 0x0038
#define NFC_REG_DEBUG 0x003C
@@ -204,10 +205,14 @@ static inline struct sunxi_nand_chip *to_sunxi_nand(struct nand_chip *nand)
* NAND Controller capabilities structure: stores NAND controller capabilities
* for distinction between compatible strings.
*
+ * @sram_through_ahb: On A33, we choose to access the internal RAM through AHB
+ * instead of MBUS (less configuration). A10, A10s, A13 and
+ * A20 use the MBUS but no extra configuration is needed.
* @reg_io_data: I/O data register
* @dma_maxburst: DMA maxburst
*/
struct sunxi_nfc_caps {
+ bool sram_through_ahb;
unsigned int reg_io_data;
unsigned int dma_maxburst;
};
@@ -363,10 +368,29 @@ static int sunxi_nfc_dma_op_prepare(struct sunxi_nfc *nfc, const void *buf,
goto err_unmap_buf;
}
- writel(readl(nfc->regs + NFC_REG_CTL) | NFC_RAM_METHOD,
- nfc->regs + NFC_REG_CTL);
+ /*
+ * On A33, we suppose the "internal RAM" (p.12 of the NFC user manual)
+ * refers to the NAND controller's internal SRAM. This memory is mapped
+ * and so is accessible from the AHB. It seems that it can also be
+ * accessed by the MBUS. MBUS accesses are mandatory when using the
+ * internal DMA instead of the external DMA engine.
+ *
+ * During DMA I/O operation, either we access this memory from the AHB
+ * by clearing the NFC_RAM_METHOD bit, or we set the bit and use the
+ * MBUS. In this case, we should also configure the MBUS DMA length
+ * NFC_REG_MDMA_CNT(0xC4) to be chunksize * nchunks. NAND I/O over MBUS
+ * are also limited to 32kiB pages.
+ */
+ if (nfc->caps->sram_through_ahb)
+ writel(readl(nfc->regs + NFC_REG_CTL) & ~NFC_RAM_METHOD,
+ nfc->regs + NFC_REG_CTL);
+ else
+ writel(readl(nfc->regs + NFC_REG_CTL) | NFC_RAM_METHOD,
+ nfc->regs + NFC_REG_CTL);
+
writel(nchunks, nfc->regs + NFC_REG_SECTOR_NUM);
writel(chunksize, nfc->regs + NFC_REG_CNT);
+
dmat = dmaengine_submit(dmad);
ret = dma_submit_error(dmat);
@@ -2176,11 +2200,21 @@ static const struct sunxi_nfc_caps sunxi_nfc_a10_caps = {
.dma_maxburst = 4,
};
+static const struct sunxi_nfc_caps sunxi_nfc_a33_caps = {
+ .sram_through_ahb = true,
+ .reg_io_data = NFC_REG_A33_IO_DATA,
+ .dma_maxburst = 8,
+};
+
static const struct of_device_id sunxi_nfc_ids[] = {
{
.compatible = "allwinner,sun4i-a10-nand",
.data = &sunxi_nfc_a10_caps,
},
+ {
+ .compatible = "allwinner,sun8i-a33-nand-controller",
+ .data = &sunxi_nfc_a33_caps,
+ },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, sunxi_nfc_ids);
--
2.19.1
