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mtd: spi-nor-core: Perform a Soft Reset on shutdown

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On probe, the SPI NOR core will put a flash in 8D-8D-8D mode if it
supports it. But Linux as of now expects to get the flash in 1S-1S-1S
mode. Handing the flash to Linux in Octal DTR mode means the kernel will
fail to detect the flash.

So, we need to reset to Power-on-Reset (POR) state before handing off
the flash. A Software Reset command can be used to do this.

One limitation of the soft reset is that it will restore state from
non-volatile registers in some flashes. This means that if the flash was
set to 8D mode in a non-volatile configuration, a soft reset won't help.
This commit assumes that we don't set any non-volatile bits anywhere,
and the flash doesn't have any non-volatile Octal DTR mode
configuration.

Since spi-nor-tiny doesn't (and likely shouldn't) have
spi_nor_soft_reset(), add a dummy spi_nor_remove() for it that does
nothing.

Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
This commit is contained in:
Pratyush Yadav
2021-06-26 00:47:24 +05:30
committed by Jagan Teki
parent a1122a3d98
commit 575caf4500
4 changed files with 98 additions and 0 deletions
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17
include/linux/mtd/spi-nor.h
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@@ -67,6 +67,8 @@
#define SPINOR_OP_CLFSR 0x50 /* Clear flag status register */
#define SPINOR_OP_RDEAR 0xc8 /* Read Extended Address Register */
#define SPINOR_OP_WREAR 0xc5 /* Write Extended Address Register */
#define SPINOR_OP_SRSTEN 0x66 /* Software Reset Enable */
#define SPINOR_OP_SRST 0x99 /* Software Reset */
/* 4-byte address opcodes - used on Spansion and some Macronix flashes. */
#define SPINOR_OP_READ_4B 0x13 /* Read data bytes (low frequency) */
@@ -562,4 +564,19 @@ device_node *spi_nor_get_flash_node(struct spi_nor *nor)
*/
int spi_nor_scan(struct spi_nor *nor);
#if CONFIG_IS_ENABLED(SPI_FLASH_TINY)
static inline int spi_nor_remove(struct spi_nor *nor)
{
return 0;
}
#else
/**
* spi_nor_remove() - perform cleanup before booting to the next stage
* @nor: the spi_nor structure
*
* Return: 0 for success, -errno for failure.
*/
int spi_nor_remove(struct spi_nor *nor);
#endif
#endif