[PATCH 1/2] mtd: spi-nor: sfdp: save a copy of the SFDP data

[Michael Walle]

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 at walle.cc>
---
 drivers/mtd/spi-nor/core.h  | 10 ++++++++
 drivers/mtd/spi-nor/sfdp.c  | 49 +++++++++++++++++++++++++++++++++++++
 include/linux/mtd/spi-nor.h |  3 +++
 3 files changed, 62 insertions(+)

diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
index 4a3f7f150b5d..668f22011b1d 100644
--- a/drivers/mtd/spi-nor/core.h
+++ b/drivers/mtd/spi-nor/core.h
@@ -407,6 +407,16 @@ 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;
diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
index 25142ec4737b..2b6c96e02532 100644
--- a/drivers/mtd/spi-nor/sfdp.c
+++ b/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 */
@@ -1263,6 +1264,8 @@ 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;
 
@@ -1285,6 +1288,9 @@ 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
@@ -1311,6 +1317,49 @@ 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;
+	}
+
+	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;
+		goto exit;
+	}
+
+	err = spi_nor_read_sfdp_dma_unsafe(nor, 0, sfdp_size, sfdp->dwords);
+	if (err < 0) {
+		dev_dbg(dev, "failed to read SFDP data\n");
+		goto exit;
+	}
+
+	nor->sfdp = sfdp;
+
 	/*
 	 * Check other parameter headers to get the latest revision of
 	 * the basic flash parameter table.
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index a0d572855444..55c550208949 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -351,6 +351,7 @@ enum spi_nor_cmd_ext {
 struct flash_info;
 struct spi_nor_manufacturer;
 struct spi_nor_flash_parameter;
+struct sfdp;
 
 /**
  * struct spi_nor - Structure for defining the SPI NOR layer
@@ -375,6 +376,7 @@ 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
@@ -404,6 +406,7 @@ 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;
 
-- 
2.20.1