Clear error flags & initialization of Spansion

This patchset updates serial flash initialization and clear error flags for Spansion SPI flash.

Testing these patches has been done on S25FL128S and High speed SPI Controller that do switch back & forth between different modes (legacy, dual, quad).

* spi_flash_scan: Since Spansion has BP# bits & QEB on the same register, preserving the original values is recommended. Otherwise, unstable behavior may occur. e.g. if the last mode used by the SPI controller was Quad read, while the new scan should use legacy. In such a case, garbage bytes may be read instead.

* clear_sr: A new function that is used to clear status register-1 of Spansion when write or erase error occur. Clearing SR is recommended to avoid problems with the next operation(s), such as Timeout! while it is already caused by the last operation but not the current one.

TODO: If applicable, the clear_sr() should be done for the other flash vendors too.

Ahmed Samir Khalil (5):
mtd: spi: Define CLSR command
mtd: spi_flash: Support clearing status register
mtd: spi_flash: Clear SR if write/erase error is flagged
mtd: spi_flash: Clear SR error flags in case of failed write
mtd: spi_flash: preserve Spansion's original value during reboot

 drivers/mtd/spi/sf_internal.h |  3 +++
 drivers/mtd/spi/spi_flash.c   | 30 +++++++++++++++++++++++++++++-
 2 files changed, 32 insertions(+), 1 deletion(-)

2.7.4

Define clear status register command to be used
in error handling.

---
 drivers/mtd/spi/sf_internal.h | 3 +++
 1 file changed, 3 insertions(+)

index 839cdbe..42f2b20 100644
@@ -71,6 +71,9 @@ enum spi_nor_option_flags {
 # define CMD_EXTNADDR_RDEAR		0xC8
 #endif
 
+/* Register access commands */
+#define CMD_CLEAR_STATUS		0x30
+
 /* Common status */
 #define STATUS_WIP			BIT(0)
 #define STATUS_QEB_WINSPAN		BIT(1)

2.7.4

A function to clear status register-1 after error
flag(s) being triggered.

---
 drivers/mtd/spi/spi_flash.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

index 34f6888..52dcb84 100644
@@ -110,6 +110,27 @@ static int write_cr(struct spi_flash *flash, u8 wc)
 
 	return 0;
 }
+
+/*
+ * Clear status register-1
+ *
+ * TODO: Check validity for the other flash vendors.
+ */
+static int clear_sr(struct spi_flash *flash)
+{
+	struct spi_slave *spi = flash->spi;
+	u8 cmd, buf;
+	int ret;
+
+	cmd = CMD_CLEAR_STATUS;
+	ret = spi_flash_cmd_write(spi, cmd, 1, buf, 1);
+	if (ret < 0) {
+		debug("SF: fail to clear status register\n");
+		return ret;
+	}
+
+	return ret;
+}
 #endif
 
 #ifdef CONFIG_SPI_FLASH_BAR

2.7.4

In case of write or erase error, flags are being triggered into status register-1. The flags should be cleared, otherwise they may lead to unstable behavior for the following operation(s).

---
 drivers/mtd/spi/spi_flash.c | 3 +++
 1 file changed, 3 insertions(+)

index 52dcb84..6f54e10 100644
@@ -353,6 +353,9 @@ int spi_flash_cmd_erase_ops(struct spi_flash *flash, u32 offset, size_t len)
 		ret = spi_flash_write_common(flash, cmd, sizeof(cmd), NULL, 0);
 		if (ret < 0) {
 			debug("SF: erase failed\n");
+#ifdef CONFIG_SPI_FLASH_SPANSION
+			clear_sr(flash);
+#endif
 			break;
 		}
 

2.7.4

If writing fail, error that is flagged into status register-1 should be cleared. Otherwise, next operation(s) may be done incorrectly/incomplete.

---
 drivers/mtd/spi/spi_flash.c | 3 +++
 1 file changed, 3 insertions(+)

index 6f54e10..b6b56fe 100644
@@ -415,6 +415,9 @@ int spi_flash_cmd_write_ops(struct spi_flash *flash, u32 offset,
 					buf + actual, chunk_len);
 		if (ret < 0) {
 			debug("SF: write failed\n");
+#ifdef CONFIG_SPI_FLASH_SPANSION
+			clear_sr(flash);
+#endif
 			break;
 		}
 

2.7.4

Spansion flash has QEB in the same status register as well. Therefore, preserve the original values while rebooting. Otherwise, some SPI controllers may be unable to access the flash correctly e.g. receive garbage bytes instead.

---
 drivers/mtd/spi/spi_flash.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

index b6b56fe..2e603ed 100644
@@ -984,7 +984,8 @@ int spi_flash_scan(struct spi_flash *flash)
 	 */
 	if (JEDEC_MFR(info) == SPI_FLASH_CFI_MFR_ATMEL ||
 	   (JEDEC_MFR(info) == SPI_FLASH_CFI_MFR_SST) ||
-	   (JEDEC_MFR(info) == SPI_FLASH_CFI_MFR_MACRONIX)) {
+	   (JEDEC_MFR(info) == SPI_FLASH_CFI_MFR_MACRONIX) ||
+	   (JEDEC_MFR(info) == SPI_FLASH_CFI_MFR_SPANSION)) {
 		u8 sr = 0;
 
 		if (JEDEC_MFR(info) == SPI_FLASH_CFI_MFR_MACRONIX) {

2.7.4