mtd: spi-nor: sfdp: save a copy of the SFDP data

Due to possible mode switching to 8D-8D-8D, it might not be possible to
read the SFDP after the initial probe. To be able to dump the SFDP via
sysfs afterwards, make a complete copy of it.
Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Tested-by: Heiko Thiery <heiko.thiery@gmail.com>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>

drivers/mtd/spi-nor/core.h

@@ -461,6 +461,16 @@ struct spi_nor_manufacturer {
 	const struct spi_nor_fixups *fixups;
 };
 
+/**
+ * struct sfdp - SFDP data
+ * @num_dwords: number of entries in the dwords array
+ * @dwords: array of double words of the SFDP data
+ */
+struct sfdp {
+	size_t	num_dwords;
+	u32	*dwords;
+};
+
 /* Manufacturer drivers. */
 extern const struct spi_nor_manufacturer spi_nor_atmel;
 extern const struct spi_nor_manufacturer spi_nor_catalyst;

drivers/mtd/spi-nor/sfdp.c

@@ -16,6 +16,7 @@
 	(((p)->parameter_table_pointer[2] << 16) | \
 	 ((p)->parameter_table_pointer[1] <<  8) | \
 	 ((p)->parameter_table_pointer[0] <<  0))
+#define SFDP_PARAM_HEADER_PARAM_LEN(p) ((p)->length * 4)
 
 #define SFDP_BFPT_ID		0xff00	/* Basic Flash Parameter Table */
 #define SFDP_SECTOR_MAP_ID	0xff81	/* Sector Map Table */
@@ -1245,6 +1246,8 @@ int spi_nor_parse_sfdp(struct spi_nor *nor)
 	struct sfdp_parameter_header *param_headers = NULL;
 	struct sfdp_header header;
 	struct device *dev = nor->dev;
+	struct sfdp *sfdp;
+	size_t sfdp_size;
 	size_t psize;
 	int i, err;
 
@@ -1267,6 +1270,9 @@ int spi_nor_parse_sfdp(struct spi_nor *nor)
 	    bfpt_header->major != SFDP_JESD216_MAJOR)
 		return -EINVAL;
 
+	sfdp_size = SFDP_PARAM_HEADER_PTP(bfpt_header) +
+		    SFDP_PARAM_HEADER_PARAM_LEN(bfpt_header);
+
 	/*
 	 * Allocate memory then read all parameter headers with a single
 	 * Read SFDP command. These parameter headers will actually be parsed
@@ -1293,6 +1299,58 @@ int spi_nor_parse_sfdp(struct spi_nor *nor)
 		}
 	}
 
+	/*
+	 * Cache the complete SFDP data. It is not (easily) possible to fetch
+	 * SFDP after probe time and we need it for the sysfs access.
+	 */
+	for (i = 0; i < header.nph; i++) {
+		param_header = &param_headers[i];
+		sfdp_size = max_t(size_t, sfdp_size,
+				  SFDP_PARAM_HEADER_PTP(param_header) +
+				  SFDP_PARAM_HEADER_PARAM_LEN(param_header));
+	}
+
+	/*
+	 * Limit the total size to a reasonable value to avoid allocating too
+	 * much memory just of because the flash returned some insane values.
+	 */
+	if (sfdp_size > PAGE_SIZE) {
+		dev_dbg(dev, "SFDP data (%zu) too big, truncating\n",
+			sfdp_size);
+		sfdp_size = PAGE_SIZE;
+	}
+
+	sfdp = devm_kzalloc(dev, sizeof(*sfdp), GFP_KERNEL);
+	if (!sfdp) {
+		err = -ENOMEM;
+		goto exit;
+	}
+
+	/*
+	 * The SFDP is organized in chunks of DWORDs. Thus, in theory, the
+	 * sfdp_size should be a multiple of DWORDs. But in case a flash
+	 * is not spec compliant, make sure that we have enough space to store
+	 * the complete SFDP data.
+	 */
+	sfdp->num_dwords = DIV_ROUND_UP(sfdp_size, sizeof(*sfdp->dwords));
+	sfdp->dwords = devm_kcalloc(dev, sfdp->num_dwords,
+				    sizeof(*sfdp->dwords), GFP_KERNEL);
+	if (!sfdp->dwords) {
+		err = -ENOMEM;
+		devm_kfree(dev, sfdp);
+		goto exit;
+	}
+
+	err = spi_nor_read_sfdp(nor, 0, sfdp_size, sfdp->dwords);
+	if (err < 0) {
+		dev_dbg(dev, "failed to read SFDP data\n");
+		devm_kfree(dev, sfdp->dwords);
+		devm_kfree(dev, sfdp);
+		goto exit;
+	}
+
+	nor->sfdp = sfdp;
+
 	/*
 	 * Check other parameter headers to get the latest revision of
 	 * the basic flash parameter table.

include/linux/mtd/spi-nor.h

@@ -383,6 +383,7 @@ struct spi_nor_flash_parameter;
  * @read_proto:		the SPI protocol for read operations
  * @write_proto:	the SPI protocol for write operations
  * @reg_proto:		the SPI protocol for read_reg/write_reg/erase operations
+ * @sfdp:		the SFDP data of the flash
  * @controller_ops:	SPI NOR controller driver specific operations.
  * @params:		[FLASH-SPECIFIC] SPI NOR flash parameters and settings.
  *                      The structure includes legacy flash parameters and
@@ -412,6 +413,7 @@ struct spi_nor {
 	bool			sst_write_second;
 	u32			flags;
 	enum spi_nor_cmd_ext	cmd_ext_type;
+	struct sfdp		*sfdp;
 
 	const struct spi_nor_controller_ops *controller_ops;