[RFC PATCH] memory: renesas-rpc-if: Correct QSPI data transfer in Manual mode

[Wolfram Sang <wsa+renesas@sang-engineering.com>]

This patch fixes 2 problems:
[1] The output warning logs and data loss when performing
mount/umount then remount the device with jffs2 format.
[2] The access width of SMWDR[0:1]/SMRDR[0:1] register is wrong.

This is the sample warning logs when performing mount/umount then
remount the device with jffs2 format:
jffs2: jffs2_scan_inode_node(): CRC failed on node at 0x031c51d4:
Read 0x00034e00, calculated 0xadb272a7

The reason for issue [1] is that the writing data seems to
get messed up.
Data is only completed when the number of bytes is divisible by 4.
If you only have 3 bytes of data left to write, 1 garbage byte
is inserted after the end of the write stream.
If you only have 2 bytes of data left to write, 2 bytes of '00'
are added into the write stream.
If you only have 1 byte of data left to write, 2 bytes of '00'
are added into the write stream. 1 garbage byte is inserted after
the end of the write stream.

To solve problem [1], data must be written continuously in serial
and the write stream ends when data is out.

Following HW manual 62.2.15, access to SMWDR0 register should be
in the same size as the transfer size specified in the SPIDE[3:0]
bits in the manual mode enable setting register (SMENR).
Be sure to access from address 0.

So, in 16-bit transfer (SPIDE[3:0]=b'1100), SMWDR0 should be
accessed by 16-bit width.
Similar to SMWDR1, SMDDR0/1 registers.
In current code, SMWDR0 register is accessed by regmap_write()
that only set up to do 32-bit width.

To solve problem [2], data must be written 16-bit or 8-bit when
transferring 1-byte or 2-byte.

Signed-off-by: Duc Nguyen <duc.nguyen.ub@renesas.com>
[wsa: refactored to use regmap only via reg_read/reg_write]
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---

Hi,

I could reproduce the issue by a simple:

  $ echo "Hello" > /dev/mtd10

The original BSP patch fixed the issue but mixed regmap-acces with
ioread/iowrite accesses. So, I refactored it to use custom regmap
accessors. This keeps the code more readable IMO. With this patch, my
custom test cases work as well as the JFFS2 remount mentioned in the
commit message. Tested on a Renesas Condor board (R-Car V3M) and a
Falcon board (R-Car V3U). I send this as RFC because this is my first
patch for the RPC code and hope for feedback. The BSP team has been
contacted as well for comments and testing. Nonetheless, this addresses
a serious issue which has caused broken boards because of writing to
unintended locations. So, I'd like to see this discussed and applied
soon if possible.

Thanks everyone,

   Wolfram


 drivers/memory/renesas-rpc-if.c | 113 ++++++++++++++++++++++----------
 include/memory/renesas-rpc-if.h |   1 +
 2 files changed, 79 insertions(+), 35 deletions(-)

diff --git a/drivers/memory/renesas-rpc-if.c b/drivers/memory/renesas-rpc-if.c
index 45eed659b0c6..77a011d5ff8c 100644
--- a/drivers/memory/renesas-rpc-if.c
+++ b/drivers/memory/renesas-rpc-if.c
@@ -160,10 +160,62 @@ static const struct regmap_access_table rpcif_volatile_table = {
 	.n_yes_ranges	= ARRAY_SIZE(rpcif_volatile_ranges),
 };
 
+
+/*
+ * Custom accessor functions to ensure SMRDR0 and SMWDR0 are always accessed
+ * with proper width. Requires SMENR_SPIDE to be correctly set before!
+ */
+static int rpcif_reg_read(void *context, unsigned int reg, unsigned int *val)
+{
+	struct rpcif *rpc = context;
+
+	if (reg == RPCIF_SMRDR0 || reg == RPCIF_SMWDR0) {
+		u32 spide = readl(rpc->base + RPCIF_SMENR) & RPCIF_SMENR_SPIDE(0xF);
+
+		if (spide == 0x8) {
+			*val = readb(rpc->base + reg);
+			return 0;
+		} else if (spide == 0xC) {
+			*val = readw(rpc->base + reg);
+			return 0;
+		} else if (spide != 0xF) {
+			return -EILSEQ;
+		}
+	}
+
+	*val = readl(rpc->base + reg);
+	return 0;
+
+}
+
+static int rpcif_reg_write(void *context, unsigned int reg, unsigned int val)
+{
+	struct rpcif *rpc = context;
+
+	if (reg == RPCIF_SMRDR0 || reg == RPCIF_SMWDR0) {
+		u32 spide = readl(rpc->base + RPCIF_SMENR) & RPCIF_SMENR_SPIDE(0xF);
+
+		if (spide == 0x8) {
+			writeb(val, rpc->base + reg);
+			return 0;
+		} else if (spide == 0xC) {
+			writew(val, rpc->base + reg);
+			return 0;
+		} else if (spide != 0xF) {
+			return -EILSEQ;
+		}
+	}
+
+	writel(val, rpc->base + reg);
+	return 0;
+}
+
 static const struct regmap_config rpcif_regmap_config = {
 	.reg_bits	= 32,
 	.val_bits	= 32,
 	.reg_stride	= 4,
+	.reg_read	= rpcif_reg_read,
+	.reg_write	= rpcif_reg_write,
 	.fast_io	= true,
 	.max_register	= RPCIF_PHYINT,
 	.volatile_table	= &rpcif_volatile_table,
@@ -173,17 +225,15 @@ int rpcif_sw_init(struct rpcif *rpc, struct device *dev)
 {
 	struct platform_device *pdev = to_platform_device(dev);
 	struct resource *res;
-	void __iomem *base;
 
 	rpc->dev = dev;
 
 	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "regs");
-	base = devm_ioremap_resource(&pdev->dev, res);
-	if (IS_ERR(base))
-		return PTR_ERR(base);
+	rpc->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(rpc->base))
+		return PTR_ERR(rpc->base);
 
-	rpc->regmap = devm_regmap_init_mmio(&pdev->dev, base,
-					    &rpcif_regmap_config);
+	rpc->regmap = devm_regmap_init(&pdev->dev, NULL, rpc, &rpcif_regmap_config);
 	if (IS_ERR(rpc->regmap)) {
 		dev_err(&pdev->dev,
 			"failed to init regmap for rpcif, error %ld\n",
@@ -354,20 +404,16 @@ void rpcif_prepare(struct rpcif *rpc, const struct rpcif_op *op, u64 *offs,
 			nbytes = op->data.nbytes;
 		rpc->xferlen = nbytes;
 
-		rpc->enable |= RPCIF_SMENR_SPIDE(rpcif_bits_set(rpc, nbytes)) |
-			RPCIF_SMENR_SPIDB(rpcif_bit_size(op->data.buswidth));
+		rpc->enable |= RPCIF_SMENR_SPIDB(rpcif_bit_size(op->data.buswidth));
 	}
 }
 EXPORT_SYMBOL(rpcif_prepare);
 
 int rpcif_manual_xfer(struct rpcif *rpc)
 {
-	u32 smenr, smcr, pos = 0, max = 4;
+	u32 smenr, smcr, pos = 0, max = rpc->bus_size == 2 ? 8 : 4;
 	int ret = 0;
 
-	if (rpc->bus_size == 2)
-		max = 8;
-
 	pm_runtime_get_sync(rpc->dev);
 
 	regmap_update_bits(rpc->regmap, RPCIF_PHYCNT,
@@ -378,37 +424,36 @@ int rpcif_manual_xfer(struct rpcif *rpc)
 	regmap_write(rpc->regmap, RPCIF_SMOPR, rpc->option);
 	regmap_write(rpc->regmap, RPCIF_SMDMCR, rpc->dummy);
 	regmap_write(rpc->regmap, RPCIF_SMDRENR, rpc->ddr);
+	regmap_write(rpc->regmap, RPCIF_SMADR, rpc->smadr);
 	smenr = rpc->enable;
 
 	switch (rpc->dir) {
 	case RPCIF_DATA_OUT:
 		while (pos < rpc->xferlen) {
-			u32 nbytes = rpc->xferlen - pos;
-			u32 data[2];
+			u32 bytes_left = rpc->xferlen - pos;
+			u32 nbytes, data[2];
 
 			smcr = rpc->smcr | RPCIF_SMCR_SPIE;
-			if (nbytes > max) {
-				nbytes = max;
+
+			/* nbytes may only be 1, 2, 4, or 8 */
+			nbytes = bytes_left >= max ? max : (1 << ilog2(bytes_left));
+			if (bytes_left > nbytes)
 				smcr |= RPCIF_SMCR_SSLKP;
-			}
+
+			smenr |= RPCIF_SMENR_SPIDE(rpcif_bits_set(rpc, nbytes));
+			regmap_write(rpc->regmap, RPCIF_SMENR, smenr);
 
 			memcpy(data, rpc->buffer + pos, nbytes);
-			if (nbytes > 4) {
+			if (nbytes == 8) {
 				regmap_write(rpc->regmap, RPCIF_SMWDR1,
 					     data[0]);
 				regmap_write(rpc->regmap, RPCIF_SMWDR0,
 					     data[1]);
-			} else if (nbytes > 2) {
+			} else {
 				regmap_write(rpc->regmap, RPCIF_SMWDR0,
 					     data[0]);
-			} else	{
-				regmap_write(rpc->regmap, RPCIF_SMWDR0,
-					     data[0] << 16);
 			}
 
-			regmap_write(rpc->regmap, RPCIF_SMADR,
-				     rpc->smadr + pos);
-			regmap_write(rpc->regmap, RPCIF_SMENR, smenr);
 			regmap_write(rpc->regmap, RPCIF_SMCR, smcr);
 			ret = wait_msg_xfer_end(rpc);
 			if (ret)
@@ -448,14 +493,16 @@ int rpcif_manual_xfer(struct rpcif *rpc)
 			break;
 		}
 		while (pos < rpc->xferlen) {
-			u32 nbytes = rpc->xferlen - pos;
-			u32 data[2];
+			u32 bytes_left = rpc->xferlen - pos;
+			u32 nbytes, data[2];
 
-			if (nbytes > max)
-				nbytes = max;
+			/* nbytes may only be 1, 2, 4, or 8 */
+			nbytes = bytes_left >= max ? max : (1 << ilog2(bytes_left));
 
 			regmap_write(rpc->regmap, RPCIF_SMADR,
 				     rpc->smadr + pos);
+			smenr &= ~RPCIF_SMENR_SPIDE(0xF);
+			smenr |= RPCIF_SMENR_SPIDE(rpcif_bits_set(rpc, nbytes));
 			regmap_write(rpc->regmap, RPCIF_SMENR, smenr);
 			regmap_write(rpc->regmap, RPCIF_SMCR,
 				     rpc->smcr | RPCIF_SMCR_SPIE);
@@ -463,18 +510,14 @@ int rpcif_manual_xfer(struct rpcif *rpc)
 			if (ret)
 				goto err_out;
 
-			if (nbytes > 4) {
+			if (nbytes == 8) {
 				regmap_read(rpc->regmap, RPCIF_SMRDR1,
 					    &data[0]);
 				regmap_read(rpc->regmap, RPCIF_SMRDR0,
 					    &data[1]);
-			} else if (nbytes > 2) {
-				regmap_read(rpc->regmap, RPCIF_SMRDR0,
-					    &data[0]);
-			} else	{
+			} else {
 				regmap_read(rpc->regmap, RPCIF_SMRDR0,
 					    &data[0]);
-				data[0] >>= 16;
 			}
 			memcpy(rpc->buffer + pos, data, nbytes);
 
diff --git a/include/memory/renesas-rpc-if.h b/include/memory/renesas-rpc-if.h
index e3e770f76f34..77c694a19149 100644
--- a/include/memory/renesas-rpc-if.h
+++ b/include/memory/renesas-rpc-if.h
@@ -59,6 +59,7 @@ struct rpcif_op {
 
 struct rpcif {
 	struct device *dev;
+	void __iomem *base;
 	void __iomem *dirmap;
 	struct regmap *regmap;
 	struct reset_control *rstc;
-- 
2.30.2