[PATCH v2] mtd: spi-nor: core: Check read CR support

* [PATCH v2] mtd: spi-nor: core: Check read CR support
@ 2025-09-19 18:15 Jakub Czapiga
  2025-11-18 12:34 ` Pratyush Yadav
  0 siblings, 1 reply; 4+ messages in thread
From: Jakub Czapiga @ 2025-09-19 18:15 UTC (permalink / raw)
  To: Tudor Ambarus
  Cc: Pratyush Yadav, Michael Walle, Miquel Raynal, Richard Weinberger,
	Vignesh Raghavendra, linux-mtd, linux-kernel, Konrad Adamczyk,
	Adeel Arshad, Mika Westerberg, Kornel Duleba, Jakub Czapiga

Some SPI controllers like Intel's one on the PCI bus do not support
opcode 35h. This opcode is used to read the Configuration Register on
SPI-NOR chips that have 16-bit Status Register configured regardless
of the controller support for it. Adding a check call in the setup step
allows disabling use of the 35h opcode and falling back to the manual
Status Registers management.

Before:
openat(AT_FDCWD, "/dev/mtd0", O_RDWR)   = 4
ioctl(4, MIXER_WRITE(6) or MEMUNLOCK, {start=0, length=0x2000000}) = -1
EOPNOTSUPP

After:
openat(AT_FDCWD, "/dev/mtd0", O_RDWR)   = 4
ioctl(4, MIXER_WRITE(6) or MEMUNLOCK, {start=0, length=0x2000000}) = 0
ioctl(4, MIXER_WRITE(5) or MEMLOCK, {start=0x1800000, length=0x800000}) = 0

Suggested-by: Adeel Arshad <adeel.arshad@intel.com>
Signed-off-by: Jakub Czapiga <czapiga@google.com>
---
Changes since v1:
- Use spi_nor_spimem_setup_op instead of spi_nor_read_cr to test opcode
- Check only for spi-mem devices
- Move check from spi_nor_setup to spi_nor_spimem_adjust_hwcaps

 drivers/mtd/spi-nor/core.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index ac4b960101cc..0c43fcca3d0a 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -2318,6 +2318,16 @@ spi_nor_spimem_adjust_hwcaps(struct spi_nor *nor, u32 *hwcaps)
 					    &params->page_programs[ppidx]))
 			*hwcaps &= ~BIT(cap);
 	}
+
+	/* Some SPI controllers might not support CR read opcode. */
+	if (!(nor->flags & SNOR_F_NO_READ_CR)) {
+		struct spi_mem_op op = SPI_NOR_RDCR_OP(nor->bouncebuf);
+
+		spi_nor_spimem_setup_op(nor, &op, nor->reg_proto);
+
+		if (spi_nor_spimem_check_op(nor, &op))
+			nor->flags |= SNOR_F_NO_READ_CR;
+	}
 }
 
 /**
-- 
2.51.0.534.gc79095c0ca-goog


______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

^ permalink raw reply related	[flat|nested] 4+ messages in thread