[v9,23/28] mtd: spi-nor-core: Perform a Soft Reset on shutdown

[jaimeliao at mxic.com.tw]

Hi Pratyush


+#ifdef CONFIG_SPI_FLASH_SOFT_RESET
+/**
+ * spi_nor_soft_reset() - perform the JEDEC Software Reset sequence
+ * @nor:                the spi_nor structure
+ *
+ * This function can be used to switch from Octal DTR mode to legacy mode 
on a
+ * flash that supports it. The soft reset is executed in Octal DTR mode.
+ *
+ * Return: 0 for success, -errno for failure.
+ */
+static int spi_nor_soft_reset(struct spi_nor *nor)
+{
+                struct spi_mem_op op;
+                int ret;
+                enum spi_nor_cmd_ext ext;
+
+                ext = nor->cmd_ext_type;
+                nor->cmd_ext_type = SPI_NOR_EXT_REPEAT;
According JEDEC, cmd_ext_type has two different types, REPEAT and INVERT.
Some Flash vendor using "INVERT" as cmd_ext_type so that it is not 
suitable for hard coding the type as REPEAT.
Sending twice reset command with different types is clumsy but useful 
before read ID for getting Flash information.
It would be great if you have any other ideas for this part.

+
+                op = (struct 
spi_mem_op)SPI_MEM_OP(SPI_MEM_OP_CMD(SPINOR_OP_SRSTEN, 0),
+                                                SPI_MEM_OP_NO_DUMMY,
+                                                SPI_MEM_OP_NO_ADDR,
+                                                SPI_MEM_OP_NO_DATA);
+                spi_nor_setup_op(nor, &op, SNOR_PROTO_8_8_8_DTR);
+                ret = spi_mem_exec_op(nor->spi, &op);
+                if (ret) {
+                                dev_warn(nor->dev, "Software reset enable 
failed: %d\n", ret);
+                                goto out;
+                }
+
+                op = (struct 
spi_mem_op)SPI_MEM_OP(SPI_MEM_OP_CMD(SPINOR_OP_SRST, 0),
+                                                SPI_MEM_OP_NO_DUMMY,
+                                                SPI_MEM_OP_NO_ADDR,
+                                                SPI_MEM_OP_NO_DATA);
+                spi_nor_setup_op(nor, &op, SNOR_PROTO_8_8_8_DTR);
+                ret = spi_mem_exec_op(nor->spi, &op);
+                if (ret) {
+                                dev_warn(nor->dev, "Software reset 
failed: %d\n", ret);
+                                goto out;
+                }
+
+                /*
+                 * 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, wait for 200ms just to be sure.
+                 */
+                udelay(SPI_NOR_SRST_SLEEP_LEN);
+
+out:
+                nor->cmd_ext_type = ext;
+                return ret;
+}


Thanks
Jaime


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