sfc: Use fixed-size buffers for MCDI NVRAM requests

The low-level MCDI code always uses 32-bit MMIO operations, and
callers must pad input and output buffers to multiples of 4 bytes.
The MCDI NVRAM functions are not doing this.  Also, their buffers are
declared as variable-length arrays with no explicit maximum length.

Switch to a fixed buffer size based on the chunk size used by the
MTD driver (which is a multiple of 4).
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/sfc/mcdi.c

@@ -804,7 +804,7 @@ int efx_mcdi_nvram_read(struct efx_nic *efx, unsigned int type,
 			loff_t offset, u8 *buffer, size_t length)
 {
 	u8 inbuf[MC_CMD_NVRAM_READ_IN_LEN];
-	u8 outbuf[MC_CMD_NVRAM_READ_OUT_LEN(length)];
+	u8 outbuf[MC_CMD_NVRAM_READ_OUT_LEN(EFX_MCDI_NVRAM_LEN_MAX)];
 	size_t outlen;
 	int rc;
 
@@ -828,7 +828,7 @@ int efx_mcdi_nvram_read(struct efx_nic *efx, unsigned int type,
 int efx_mcdi_nvram_write(struct efx_nic *efx, unsigned int type,
 			   loff_t offset, const u8 *buffer, size_t length)
 {
-	u8 inbuf[MC_CMD_NVRAM_WRITE_IN_LEN(length)];
+	u8 inbuf[MC_CMD_NVRAM_WRITE_IN_LEN(EFX_MCDI_NVRAM_LEN_MAX)];
 	int rc;
 
 	MCDI_SET_DWORD(inbuf, NVRAM_WRITE_IN_TYPE, type);
@@ -838,7 +838,8 @@ int efx_mcdi_nvram_write(struct efx_nic *efx, unsigned int type,
 
 	BUILD_BUG_ON(MC_CMD_NVRAM_WRITE_OUT_LEN != 0);
 
-	rc = efx_mcdi_rpc(efx, MC_CMD_NVRAM_WRITE, inbuf, sizeof(inbuf),
+	rc = efx_mcdi_rpc(efx, MC_CMD_NVRAM_WRITE, inbuf,
+			  ALIGN(MC_CMD_NVRAM_WRITE_IN_LEN(length), 4),
 			  NULL, 0, NULL);
 	if (rc)
 		goto fail;

drivers/net/sfc/mcdi.h

@@ -111,6 +111,7 @@ extern int efx_mcdi_nvram_read(struct efx_nic *efx, unsigned int type,
 extern int efx_mcdi_nvram_write(struct efx_nic *efx, unsigned int type,
 				loff_t offset, const u8 *buffer,
 				size_t length);
+#define EFX_MCDI_NVRAM_LEN_MAX 128
 extern int efx_mcdi_nvram_erase(struct efx_nic *efx, unsigned int type,
 				loff_t offset, size_t length);
 extern int efx_mcdi_nvram_update_finish(struct efx_nic *efx,

drivers/net/sfc/mtd.c

@@ -23,7 +23,6 @@
 #include "mcdi_pcol.h"
 
 #define EFX_SPI_VERIFY_BUF_LEN 16
-#define EFX_MCDI_CHUNK_LEN 128
 
 struct efx_mtd_partition {
 	struct mtd_info mtd;
@@ -428,7 +427,7 @@ static int siena_mtd_read(struct mtd_info *mtd, loff_t start,
 	int rc = 0;
 
 	while (offset < end) {
-		chunk = min_t(size_t, end - offset, EFX_MCDI_CHUNK_LEN);
+		chunk = min_t(size_t, end - offset, EFX_MCDI_NVRAM_LEN_MAX);
 		rc = efx_mcdi_nvram_read(efx, part->mcdi.nvram_type, offset,
 					 buffer, chunk);
 		if (rc)
@@ -491,7 +490,7 @@ static int siena_mtd_write(struct mtd_info *mtd, loff_t start,
 	}
 
 	while (offset < end) {
-		chunk = min_t(size_t, end - offset, EFX_MCDI_CHUNK_LEN);
+		chunk = min_t(size_t, end - offset, EFX_MCDI_NVRAM_LEN_MAX);
 		rc = efx_mcdi_nvram_write(efx, part->mcdi.nvram_type, offset,
 					  buffer, chunk);
 		if (rc)