linux-kernel - [PATCH v2 1/3] mtd: spi-nor: sfdp: introduce smpt_read

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Message-Id: <20251105-s25fs-s-smpt-fixup-v2-1-c0fbd0f05ce7@infineon.com>
Date: Wed, 05 Nov 2025 16:47:58 +0900
From: Takahiro Kuwano <tkuw584924@...il.com>
To: Tudor Ambarus <tudor.ambarus@...aro.org>, 
 Pratyush Yadav <pratyush@...nel.org>, Michael Walle <mwalle@...nel.org>, 
 Miquel Raynal <miquel.raynal@...tlin.com>, 
 Richard Weinberger <richard@....at>, Vignesh Raghavendra <vigneshr@...com>, 
 Marek Vasut <marek.vasut+renesas@...lbox.org>
Cc: linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 Takahiro Kuwano <Takahiro.Kuwano@...ineon.com>, tkuw584924@...il.com
Subject: [PATCH v2 1/3] mtd: spi-nor: sfdp: introduce smpt_read_dummy fixup
 hook

SMPT contains config detection info that describes opcode, address, and
dummy cycles to read sector map config. The dummy cycles parameter can
be SMPT_CMD_READ_DUMMY_IS_VARIABLE and in that case nor->read_dummy
(initialized as 0) is used. In Infineon flash chips, Read Any Register
command with variable dummy cycle is defined in SMPT. S25Hx/S28Hx flash
has 0 dummy cycle by default to read volatile regiters and
nor->read_dummy can work. S25FS-S flash has 8 dummy cycles so we need a
hook that can fix dummy cycles with actually used value.

Inroduce smpt_read_dummy() in struct spi_nor_fixups. It is called when
the dummy cycle field in SMPT config detection is 'varialble'.

Reviewed-by: Tudor Ambarus <tudor.ambarus@...aro.org>
Tested-by: Marek Vasut <marek.vasut+renesas@...lbox.org> # S25FS512S
Signed-off-by: Takahiro Kuwano <Takahiro.Kuwano@...ineon.com>
---
 drivers/mtd/spi-nor/core.h |  3 +++
 drivers/mtd/spi-nor/sfdp.c | 18 ++++++++++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
index ceff412f7d65ab7b856795ca5c092cddbf598cd6..5ad46d95d09cc9d527f71579a71eed210e726f68 100644
--- a/drivers/mtd/spi-nor/core.h
+++ b/drivers/mtd/spi-nor/core.h
@@ -409,6 +409,8 @@ struct spi_nor_flash_parameter {
  *                flash parameters when information provided by the flash_info
  *                table is incomplete or wrong.
  * @post_bfpt: called after the BFPT table has been parsed
+ * @smpt_read_dummy: called during SMPT table is being parsed. Used to fix the
+ *                   number of dummy cycles in read register ops.
  * @post_sfdp: called after SFDP has been parsed (is also called for SPI NORs
  *             that do not support RDSFDP). Typically used to tweak various
  *             parameters that could not be extracted by other means (i.e.
@@ -426,6 +428,7 @@ struct spi_nor_fixups {
 	int (*post_bfpt)(struct spi_nor *nor,
 			 const struct sfdp_parameter_header *bfpt_header,
 			 const struct sfdp_bfpt *bfpt);
+	void (*smpt_read_dummy)(const struct spi_nor *nor, u8 *read_dummy);
 	int (*post_sfdp)(struct spi_nor *nor);
 	int (*late_init)(struct spi_nor *nor);
 };
diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c
index 21727f9a4ac6926080a116e30830c9533122fdad..9a47dcaca06ae2ad85ac8503658083b1d56d8b96 100644
--- a/drivers/mtd/spi-nor/sfdp.c
+++ b/drivers/mtd/spi-nor/sfdp.c
@@ -699,6 +699,17 @@ static u8 spi_nor_smpt_addr_nbytes(const struct spi_nor *nor, const u32 settings
 	}
 }
 
+static void spi_nor_smpt_read_dummy_fixups(const struct spi_nor *nor,
+					   u8 *read_dummy)
+{
+	if (nor->manufacturer && nor->manufacturer->fixups &&
+	    nor->manufacturer->fixups->smpt_read_dummy)
+		nor->manufacturer->fixups->smpt_read_dummy(nor, read_dummy);
+
+	if (nor->info->fixups && nor->info->fixups->smpt_read_dummy)
+		nor->info->fixups->smpt_read_dummy(nor, read_dummy);
+}
+
 /**
  * spi_nor_smpt_read_dummy() - return the configuration detection command read
  *			       latency, in clock cycles.
@@ -711,8 +722,11 @@ static u8 spi_nor_smpt_read_dummy(const struct spi_nor *nor, const u32 settings)
 {
 	u8 read_dummy = SMPT_CMD_READ_DUMMY(settings);
 
-	if (read_dummy == SMPT_CMD_READ_DUMMY_IS_VARIABLE)
-		return nor->read_dummy;
+	if (read_dummy == SMPT_CMD_READ_DUMMY_IS_VARIABLE) {
+		read_dummy = nor->read_dummy;
+		spi_nor_smpt_read_dummy_fixups(nor, &read_dummy);
+	}
+
 	return read_dummy;
 }
 

-- 
2.34.1