[U-Boot] [PATCH 2/5] sf: Add status register protect for STMICRO, SST

[George McCollister]

STMICRO parts such as M25PX64 and SST parts such as SST26VF032B support
a single status register protect bit. When set this bit cause writes to
the status register to be blocked when the write protect signal is low.

Implement sr_protect for these devices.

Signed-off-by: George McCollister <george.mccollister at gmail.com>
---
 drivers/mtd/spi/sf_internal.h |  1 +
 drivers/mtd/spi/spi_flash.c   | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/drivers/mtd/spi/sf_internal.h b/drivers/mtd/spi/sf_internal.h
index cde4cfb..1b576e8 100644
--- a/drivers/mtd/spi/sf_internal.h
+++ b/drivers/mtd/spi/sf_internal.h
@@ -81,6 +81,7 @@ enum spi_nor_option_flags {
 #define SR_BP0				BIT(2)  /* Block protect 0 */
 #define SR_BP1				BIT(3)  /* Block protect 1 */
 #define SR_BP2				BIT(4)  /* Block protect 2 */
+#define SR_SRP0				BIT(7)	/* Status register protect 0 */
 
 /* Flash timeout values */
 #define SPI_FLASH_PROG_TIMEOUT		(2 * CONFIG_SYS_HZ)
diff --git a/drivers/mtd/spi/spi_flash.c b/drivers/mtd/spi/spi_flash.c
index 7f6e9ae..0e33901 100644
--- a/drivers/mtd/spi/spi_flash.c
+++ b/drivers/mtd/spi/spi_flash.c
@@ -837,6 +837,40 @@ int stm_unlock(struct spi_flash *flash, u32 ofs, size_t len)
 
 	return 0;
 }
+
+/*
+ * Set status register protection method for parts with one protection bit
+ *
+ * Returns negative on errors, 0 on success.
+ */
+int stm_sr_protect(struct spi_flash *flash, enum srp_method method)
+{
+	uint8_t status_old, status_new;
+	u8 mask = SR_SRP0;
+	u8 val;
+	int ret;
+
+	ret = read_sr(flash, &status_old);
+	if (ret < 0)
+		return ret;
+
+	switch (method) {
+	case SRP_SOFTWARE:
+		val = 0;
+		break;
+	case SRP_HARDWARE:
+		val = SR_SRP0;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	status_new = (status_old & ~mask) | val;
+
+	write_sr(flash, status_new);
+
+	return 0;
+}
 #endif
 
 
@@ -1125,6 +1159,7 @@ int spi_flash_scan(struct spi_flash *flash)
 		flash->flash_lock = stm_lock;
 		flash->flash_unlock = stm_unlock;
 		flash->flash_is_locked = stm_is_locked;
+		flash->sr_protect = stm_sr_protect;
 #endif
 		break;
 	default:
-- 
2.9.3