[RFC PATCH v5 6/6] mtd: spi-nor: parse SFDP 4-byte Address Instruction Table

[Cyrille Pitchen <cyrille.pitchen@atmel.com>]

This patch adds supports for SFDP (JESD216B) 4-byte Address Instruction
Table. This table is optional but when available, we parse it to get the
4-byte address op codes supported by the memory.
Using these op codes is stateless as opposed to entering the 4-byte
address mode or setting the Base Address Register (BAR).

Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
---
 drivers/mtd/spi-nor/spi-nor.c | 166 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 165 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index ce8722055a9c..ea044efc4e6d 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -1899,6 +1899,7 @@ struct sfdp_parameter_header {
 
 
 #define SFDP_BFPT_ID		0xff00u	/* Basic Flash Parameter Table */
+#define SFDP_4BAIT_ID		0xff84u	/* 4-byte Address Instruction Table */
 
 #define SFDP_SIGNATURE		0x50444653u
 #define SFDP_JESD216_MAJOR	1
@@ -2241,6 +2242,149 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
 	return 0;
 }
 
+struct sfdp_4bait {
+	/* The hardware capability. */
+	u32		hwcaps;
+
+	/*
+	 * The <supported_bit> bit in DWORD1 of the 4BAIT tells us whether
+	 * the associated 4-byte address op code is supported.
+	 */
+	u32		supported_bit;
+};
+
+static int spi_nor_parse_4bait(struct spi_nor *nor,
+			       const struct sfdp_parameter_header *param_header,
+			       struct spi_nor_flash_parameter *params)
+{
+	static const struct sfdp_4bait reads[] = {
+		{ SNOR_HWCAPS_READ,		BIT(0) },
+		{ SNOR_HWCAPS_READ_FAST,	BIT(1) },
+		{ SNOR_HWCAPS_READ_1_1_2,	BIT(2) },
+		{ SNOR_HWCAPS_READ_1_2_2,	BIT(3) },
+		{ SNOR_HWCAPS_READ_1_1_4,	BIT(4) },
+		{ SNOR_HWCAPS_READ_1_4_4,	BIT(5) },
+		{ SNOR_HWCAPS_READ_1_1_1_DTR,	BIT(13) },
+		{ SNOR_HWCAPS_READ_1_2_2_DTR,	BIT(14) },
+		{ SNOR_HWCAPS_READ_1_4_4_DTR,	BIT(15) },
+	};
+	static const struct sfdp_4bait programs[] = {
+		{ SNOR_HWCAPS_PP,		BIT(6) },
+		{ SNOR_HWCAPS_PP_1_1_4,		BIT(7) },
+		{ SNOR_HWCAPS_PP_1_4_4,		BIT(8) },
+	};
+	static const struct sfdp_4bait erases[SNOR_CMD_ERASE_MAX] = {
+		{ 0u /* not used */,		BIT(9) },
+		{ 0u /* not used */,		BIT(10) },
+		{ 0u /* not used */,		BIT(11) },
+		{ 0u /* not used */,		BIT(12) },
+	};
+	u32 dwords[2], addr, discard_hwcaps, read_hwcaps, pp_hwcaps, erase_mask;
+	struct spi_nor_erase_map *map = &nor->erase_map;
+	int i, err;
+
+	if (param_header->major != SFDP_JESD216_MAJOR ||
+	    param_header->length < ARRAY_SIZE(dwords))
+		return -EINVAL;
+
+	/* Read the 4-byte Address Instruction Table. */
+	addr = SFDP_PARAM_HEADER_PTP(param_header);
+	err = spi_nor_read_sfdp(nor, addr, sizeof(dwords), dwords);
+	if (err)
+		return err;
+
+	/* Fix endianness of the 4BAIT DWORDs. */
+	for (i = 0; i < ARRAY_SIZE(dwords); i++)
+		dwords[i] = le32_to_cpu(dwords[i]);
+
+	/*
+	 * Compute the subset of (Fast) Read commands for which the 4-byte
+	 * version is supported.
+	 */
+	discard_hwcaps = 0;
+	read_hwcaps = 0;
+	for (i = 0; i < ARRAY_SIZE(reads); i++) {
+		const struct sfdp_4bait *read = &reads[i];
+
+		discard_hwcaps |= read->hwcaps;
+		if ((params->hwcaps.mask & read->hwcaps) &&
+		    (dwords[0] & read->supported_bit))
+			read_hwcaps |= read->hwcaps;
+	}
+
+	/*
+	 * Compute the subset of Page Program commands for which the 4-byte
+	 * version is supported.
+	 */
+	pp_hwcaps = 0;
+	for (i = 0; i < ARRAY_SIZE(programs); i++) {
+		const struct sfdp_4bait *program = &programs[i];
+
+		discard_hwcaps |= program->hwcaps;
+		if ((params->hwcaps.mask & program->hwcaps) &&
+		    (dwords[0] & program->supported_bit))
+			pp_hwcaps |= program->hwcaps;
+	}
+
+	/*
+	 * Compute the subet of Sector Erase commands for which the 4-byte
+	 * version is supported.
+	 */
+	erase_mask = 0;
+	for (i = 0; i < SNOR_CMD_ERASE_MAX; i++) {
+		const struct sfdp_4bait *erase = &erases[i];
+
+		if ((map->commands[i].size > 0) &&
+		    (dwords[0] & erase->supported_bit))
+			erase_mask |= BIT(i);
+	}
+
+	/*
+	 * We need at least one 4-byte op code per read, program and erase
+	 * operation; the .read(), .write() and .erase() hooks share the
+	 * nor->addr_width value.
+	 */
+	if (!read_hwcaps || !pp_hwcaps || !erase_mask)
+		return 0;
+
+	/*
+	 * Discard all operations from the 4-byte instruction set which are
+	 * not supported by this memory.
+	 */
+	params->hwcaps.mask &= ~discard_hwcaps;
+	params->hwcaps.mask |= (read_hwcaps | pp_hwcaps);
+
+	/* Use the 4-byte address instruction set. */
+	for (i = 0; i < SNOR_CMD_READ_MAX; i++) {
+		struct spi_nor_read_command *read_cmd = &params->reads[i];
+
+		read_cmd->opcode = spi_nor_convert_3to4_read(read_cmd->opcode);
+	}
+	for (i = 0; i < SNOR_CMD_PP_MAX; i++) {
+		struct spi_nor_pp_command *pp_cmd = &params->page_programs[i];
+
+		pp_cmd->opcode = spi_nor_convert_3to4_program(pp_cmd->opcode);
+	}
+	for (i = 0; i < SNOR_CMD_ERASE_MAX; i++) {
+		struct spi_nor_erase_command *erase_cmd = &map->commands[i];
+
+		if (erase_mask & BIT(i))
+			erase_cmd->opcode = (dwords[1] >> (i * 8)) & 0xFF;
+		else
+			spi_nor_set_erase_command(erase_cmd, 0u, 0xFF);
+	}
+
+	/*
+	 * We set nor->addr_width here to skip spi_nor_set_4byte_opcodes()
+	 * later because this latest function implements a legacy quirk for
+	 * the erase size of Spansion memory. However this quirk is no longer
+	 * needed with new SFDP compliant memories.
+	 */
+	nor->addr_width = 4;
+	nor->flags |= SNOR_F_4B_OPCODES;
+	return 0;
+}
+
 static int spi_nor_parse_sfdp(struct spi_nor *nor,
 			      struct spi_nor_flash_parameter *params)
 {
@@ -2308,6 +2452,23 @@ static int spi_nor_parse_sfdp(struct spi_nor *nor,
 	if (err)
 		goto exit;
 
+	/* Parse other parameter headers. */
+	for (i = 0; i < header.nph; i++) {
+		param_header = &param_headers[i];
+
+		switch (SFDP_PARAM_HEADER_ID(param_header)) {
+		case SFDP_4BAIT_ID:
+			err = spi_nor_parse_4bait(nor, param_header, params);
+			break;
+
+		default:
+			break;
+		}
+
+		if (err)
+			goto exit;
+	}
+
 exit:
 	kfree(param_headers);
 	return err;
@@ -2885,7 +3046,10 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
 	if (ret)
 		return ret;
 
-	if (info->addr_width)
+	if (nor->addr_width)
+		/* already configured by spi_nor_setup() */
+		;
+	else if (info->addr_width)
 		nor->addr_width = info->addr_width;
 	else if (mtd->size > 0x1000000) {
 		/* enable 4-byte addressing if the device exceeds 16MiB */
-- 
2.9.3