From 70dd83d737d8900b2d98db6dc6b928c596334d37 Mon Sep 17 00:00:00 2001
From: Chen-Tsung Hsieh <chentsung@chromium.org>
Date: Wed, 26 Jan 2022 15:32:26 +0800
Subject: [PATCH] mtd: spi-nor: core: Check written SR value in spi_nor_write_16bit_sr_and_check()
Git-commit: 70dd83d737d8900b2d98db6dc6b928c596334d37
Patch-mainline: v5.19-rc1
References: git-fixes

Read back Status Register 1 to ensure that the written byte match the
received value and return -EIO if read back test failed.

Without this patch, spi_nor_write_16bit_sr_and_check() only check the
second half of the 16bit. It causes errors like spi_nor_sr_unlock()
return success incorrectly when spi_nor_write_16bit_sr_and_check()
doesn't write SR successfully.

Fixes: 39d1e3340c73 ("mtd: spi-nor: Fix clearing of QE bit on lock()/unlock()")
Signed-off-by: Chen-Tsung Hsieh <chentsung@chromium.org>
Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Michael Walle <michael@walle.cc>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Acked-by: Pratyush Yadav <p.yadav@ti.com>
Link: https://lore.kernel.org/r/20220126073227.3401275-1-chentsung@chromium.org
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/mtd/spi-nor/core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index b4f141ad9c9c..c1630131c734 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -788,6 +788,15 @@ static int spi_nor_write_16bit_sr_and_check(struct spi_nor *nor, u8 sr1)
 	if (ret)
 		return ret;
 
+	ret = spi_nor_read_sr(nor, sr_cr);
+	if (ret)
+		return ret;
+
+	if (sr1 != sr_cr[0]) {
+		dev_dbg(nor->dev, "SR: Read back test failed\n");
+		return -EIO;
+	}
+
 	if (nor->flags & SNOR_F_NO_READ_CR)
 		return 0;
 
-- 
2.35.3