[PATCH v4 12/16] mtd: spi-nor: perform a Soft Reset on shutdown

Pratyush Yadav
2020-04-24T18:53:46Z

A Software Reset sequence will return the flash to Power-on-Reset (POR)
state. It consists of two commands: Soft Reset Enable and Soft Reset.

Perform a Soft Reset on shutdown on flashes that support it so that the
flash can be reset to its initial state and any configurations made by
spi-nor (given that they're only done in volatile registers) will be
reset. This will hand back the flash in pristine state for any further
operations on it.

Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
---
drivers/mtd/spi-nor/core.c | 45 +++++++++++++++++++++++++++++++++++++
drivers/mtd/spi-nor/core.h | 2 ++
include/linux/mtd/spi-nor.h | 2 ++
3 files changed, 49 insertions(+)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index c75765f09d62..b0f94d6d28bf 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -40,6 +40,9 @@

#define SPI_NOR_MAX_ADDR_WIDTH 4

+#define SPI_NOR_SRST_SLEEP_MIN 200
+#define SPI_NOR_SRST_SLEEP_MAX 400
+
/**
* spi_nor_get_cmd_ext() - Get the command opcode extension based on the
* extension type.
@@ -3189,6 +3192,41 @@ static int spi_nor_init(struct spi_nor *nor)
return 0;
}

+static void spi_nor_soft_reset(struct spi_nor *nor)
+{
+ struct spi_mem_op op;
+ int ret;
+
+ op = (struct spi_mem_op)SPI_MEM_OP(SPI_MEM_OP_CMD(SPINOR_OP_SRSTEN, 8),
+ SPI_MEM_OP_NO_DUMMY,
+ SPI_MEM_OP_NO_ADDR,
+ SPI_MEM_OP_NO_DATA);
+ spi_nor_spimem_setup_op(nor, &op, SNOR_PROTO_8_8_8_DTR);
+ ret = spi_mem_exec_op(nor->spimem, &op);
+ if (ret) {
+ dev_warn(nor->dev, "Software reset failed: %d\n", ret);
+ return;
+ }
+
+ op = (struct spi_mem_op)SPI_MEM_OP(SPI_MEM_OP_CMD(SPINOR_OP_SRST, 8),
+ SPI_MEM_OP_NO_DUMMY,
+ SPI_MEM_OP_NO_ADDR,
+ SPI_MEM_OP_NO_DATA);
+ spi_nor_spimem_setup_op(nor, &op, SNOR_PROTO_8_8_8_DTR);
+ ret = spi_mem_exec_op(nor->spimem, &op);
+ if (ret) {
+ dev_warn(nor->dev, "Software reset failed: %d\n", ret);
+ return;
+ }
+
+ /*
+ * Software Reset is not instant, and the delay varies from flash to
+ * flash. Looking at a few flashes, most range somewhere below 100
+ * microseconds. So, sleep for a range of 200-400 us.
+ */
+ usleep_range(SPI_NOR_SRST_SLEEP_MIN, SPI_NOR_SRST_SLEEP_MAX);
+}
+
/* mtd resume handler */
static void spi_nor_resume(struct mtd_info *mtd)
{
@@ -3208,6 +3246,10 @@ void spi_nor_restore(struct spi_nor *nor)
if (nor->addr_width == 4 && !(nor->flags & SNOR_F_4B_OPCODES) &&
nor->flags & SNOR_F_BROKEN_RESET)
nor->params->set_4byte_addr_mode(nor, false);
+
+ if (nor->info->flags & SPI_NOR_OCTAL_DTR_READ &&
+ nor->flags & SNOR_F_SOFT_RESET)
+ spi_nor_soft_reset(nor);
}
EXPORT_SYMBOL_GPL(spi_nor_restore);

@@ -3394,6 +3436,9 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
nor->flags |= SNOR_F_HAS_SR_TB_BIT6;
}

+ if (info->flags & SPI_NOR_SOFT_RESET)
+ nor->flags |= SNOR_F_SOFT_RESET;
+
if (info->flags & NO_CHIP_ERASE)
nor->flags |= SNOR_F_NO_OP_CHIP_ERASE;
if (info->flags & USE_CLSR)
diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
index 6338d32a0d77..86c31357b321 100644
--- a/drivers/mtd/spi-nor/core.h
+++ b/drivers/mtd/spi-nor/core.h
@@ -26,6 +26,7 @@ enum spi_nor_option_flags {
SNOR_F_HAS_SR_TB_BIT6 = BIT(11),
SNOR_F_HAS_4BIT_BP = BIT(12),
SNOR_F_HAS_SR_BP3_BIT6 = BIT(13),
+ SNOR_F_SOFT_RESET = BIT(14),
};

struct spi_nor_read_command {
@@ -321,6 +322,7 @@ struct flash_info {
* Must be used with SPI_NOR_4BIT_BP.
*/
#define SPI_NOR_OCTAL_DTR_READ BIT(19) /* Flash supports octal DTR Read. */
+#define SPI_NOR_SOFT_RESET BIT(20) /* Flash supports soft reset command */

/* Part specific fixup hooks. */
const struct spi_nor_fixups *fixups;
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index 9bb41d9401c6..7b828ee1c036 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -51,6 +51,8 @@
#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) */