mtd: spi-nor-core: Perform a Soft Reset on shutdown
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>
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index b2159f6..29ce175 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -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 @@
*/
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