memory: renesas-rpc-if: Fix HF/OSPI data transfer in Manual Mode

HyperFlash devices fail to probe:

    rpc-if-hyperflash rpc-if-hyperflash: probing of hyperbus device failed

In HyperFlash or Octal-SPI Flash mode, the Transfer Data Enable bits
(SPIDE) in the Manual Mode Enable Setting Register (SMENR) are derived
from half of the transfer size, cfr. the rpcif_bits_set() helper
function.  However, rpcif_reg_{read,write}() does not take the bus size
into account, and does not double all Manual Mode Data Register access
sizes when communicating with a HyperFlash or Octal-SPI Flash device.

Fix this, and avoid the back-and-forth conversion between transfer size
and Transfer Data Enable bits, by explicitly storing the transfer size
in struct rpcif, and using that value to determine access size in
rpcif_reg_{read,write}().

Enforce that the "high" Manual Mode Read/Write Data Registers
(SM[RW]DR1) are only used for 8-byte data accesses.
While at it, forbid writing to the Manual Mode Read Data Registers,
as they are read-only.

Fixes: fff53a55 ("memory: renesas-rpc-if: Correct QSPI data transfer in Manual mode")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/cde9bfacf704c81865f57b15d1b48a4793da4286.1649681476.git.geert+renesas@glider.be
Link: https://lore.kernel.org/r/20220420070526.9367-1-krzysztof.kozlowski@linaro.org'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/memory/renesas-rpc-if.c

@@ -164,25 +164,39 @@ static const struct regmap_access_table rpcif_volatile_table = {
 
 
 /*
- * Custom accessor functions to ensure SMRDR0 and SMWDR0 are always accessed
- * with proper width. Requires SMENR_SPIDE to be correctly set before!
+ * Custom accessor functions to ensure SM[RW]DR[01] are always accessed with
+ * proper width.  Requires rpcif.xfer_size 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) {
+	switch (reg) {
+	case RPCIF_SMRDR0:
+	case RPCIF_SMWDR0:
+		switch (rpc->xfer_size) {
+		case 1:
 			*val = readb(rpc->base + reg);
 			return 0;
-		} else if (spide == 0xC) {
+
+		case 2:
 			*val = readw(rpc->base + reg);
 			return 0;
-		} else if (spide != 0xF) {
+
+		case 4:
+		case 8:
+			*val = readl(rpc->base + reg);
+			return 0;
+
+		default:
 			return -EILSEQ;
 		}
+
+	case RPCIF_SMRDR1:
+	case RPCIF_SMWDR1:
+		if (rpc->xfer_size != 8)
+			return -EILSEQ;
+		break;
 	}
 
 	*val = readl(rpc->base + reg);
@@ -193,18 +207,34 @@ 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) {
+	switch (reg) {
+	case RPCIF_SMWDR0:
+		switch (rpc->xfer_size) {
+		case 1:
 			writeb(val, rpc->base + reg);
 			return 0;
-		} else if (spide == 0xC) {
+
+		case 2:
 			writew(val, rpc->base + reg);
 			return 0;
-		} else if (spide != 0xF) {
+
+		case 4:
+		case 8:
+			writel(val, rpc->base + reg);
+			return 0;
+
+		default:
 			return -EILSEQ;
 		}
+
+	case RPCIF_SMWDR1:
+		if (rpc->xfer_size != 8)
+			return -EILSEQ;
+		break;
+
+	case RPCIF_SMRDR0:
+	case RPCIF_SMRDR1:
+		return -EPERM;
 	}
 
 	writel(val, rpc->base + reg);
@@ -469,6 +499,7 @@ int rpcif_manual_xfer(struct rpcif *rpc)
 
 			smenr |= RPCIF_SMENR_SPIDE(rpcif_bits_set(rpc, nbytes));
 			regmap_write(rpc->regmap, RPCIF_SMENR, smenr);
+			rpc->xfer_size = nbytes;
 
 			memcpy(data, rpc->buffer + pos, nbytes);
 			if (nbytes == 8) {
@@ -533,6 +564,7 @@ int rpcif_manual_xfer(struct rpcif *rpc)
 			regmap_write(rpc->regmap, RPCIF_SMENR, smenr);
 			regmap_write(rpc->regmap, RPCIF_SMCR,
 				     rpc->smcr | RPCIF_SMCR_SPIE);
+			rpc->xfer_size = nbytes;
 			ret = wait_msg_xfer_end(rpc);
 			if (ret)
 				goto err_out;

include/memory/renesas-rpc-if.h

@@ -72,6 +72,7 @@ struct rpcif {
 	enum rpcif_type type;
 	enum rpcif_data_dir dir;
 	u8 bus_size;
+	u8 xfer_size;
 	void *buffer;
 	u32 xferlen;
 	u32 smcr;