Hi Tudor,

On 08/07/20 04:10PM, Tudor.Ambarus@microchip.com wrote:

On 6/23/20 9:30 PM, Pratyush Yadav wrote:

quoted

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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 <redacted>
---
 drivers/mtd/spi-nor/core.c  | 42 +++++++++++++++++++++++++++++++++++++
 include/linux/mtd/spi-nor.h |  2 ++
 2 files changed, 44 insertions(+)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 4a1f6b343534..27ad9bab06dc 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.

@@ -3201,6 +3204,41 @@ 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)
 {

@@ -3220,6 +3258,10 @@ 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 &&

Why this limitation? Can't we make the software reset available for all
the modes?

Because I wrote the function spi_nor_soft_reset() from the perspective 
of xSPI support, and the xSPI spec only cares about the 8D-8D-8D version 
of the soft reset.

BFPT says we can execute it on 1, 2, 4, or 8 wires depending on the mode 
so I guess we can support a generalized version as well. Will fix.

quoted

+           nor->flags & SNOR_F_SOFT_RESET)
+               spi_nor_soft_reset(nor);
 }
 EXPORT_SYMBOL_GPL(spi_nor_restore);

diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index cd549042c53d..299685d15dc2 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) */

-- 
Regards,
Pratyush Yadav

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