linux-kernel - [PATCH 2/3] mtd: spi-nor: sst: add missing write

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Date:   Fri, 11 Sep 2020 16:47:02 +0200
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     tudor.ambarus@...rochip.com, miquel.raynal@...tlin.com,
        richard@....at, vigneshr@...com,
        sergei.shtylyov@...entembedded.com, boris.brezillon@...labora.com,
        michael@...le.cc, j.neuschaefer@....net
Cc:     linux-mtd@...ts.infradead.org, kernel@...gutronix.de,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/3] mtd: spi-nor: sst: add missing write_enable

According the datasheet [1] the WEL is automatically reset after the
Byte-Program instruction completion. So if we program the device with
byte-size set to 32 and starting from an odd address only the first and
the last byte is written. Fix this by (re-)anble the write support for
the first SPINOR_OP_AAI_WP sequence.

[1] http://ww1.microchip.com/downloads/en/DeviceDoc/20005044C.pdf;
    "4.3.2 WRITE ENABLE LATCH (WEL)"

Signed-off-by: Marco Felsch <m.felsch@...gutronix.de>
---
 drivers/mtd/spi-nor/sst.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/mtd/spi-nor/sst.c b/drivers/mtd/spi-nor/sst.c
index e0af6d25d573..644252e27a2a 100644
--- a/drivers/mtd/spi-nor/sst.c
+++ b/drivers/mtd/spi-nor/sst.c
@@ -79,6 +79,13 @@ static int sst_write(struct mtd_info *mtd, loff_t to, size_t len,
 
 	/* Write out most of the data here. */
 	for (; actual < len - 1; actual += 2) {
+		/* Enable write support if odd address was written before */
+		if (actual == 1) {
+			ret = spi_nor_write_enable(nor);
+			if (ret)
+				goto out;
+		}
+
 		nor->program_opcode = SPINOR_OP_AAI_WP;
 
 		/* write two bytes. */
-- 
2.20.1