[PATCH 4.18 143/228] spi: sh-msiof: Fix handling of write value for SISTR register

[Greg Kroah-Hartman]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hiromitsu Yamasaki <hiromitsu.yamasaki.ym@xxxxxxxxxxx>

commit 31a5fae4c5a009898da6d177901d5328051641ff upstream.

This patch changes writing to the SISTR register according to the H/W
user's manual.

The TDREQ bit and RDREQ bits of SISTR are read-only, and must be written
their initial values of zero.

Signed-off-by: Hiromitsu Yamasaki <hiromitsu.yamasaki.ym@xxxxxxxxxxx>
[geert: reword]
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/drivers/spi/spi-sh-msiof.c
+++ b/drivers/spi/spi-sh-msiof.c
@@ -396,7 +396,8 @@ static void sh_msiof_spi_set_mode_regs(s
 
 static void sh_msiof_reset_str(struct sh_msiof_spi_priv *p)
 {
-	sh_msiof_write(p, STR, sh_msiof_read(p, STR));
+	sh_msiof_write(p, STR,
+		       sh_msiof_read(p, STR) & ~(STR_TDREQ | STR_RDREQ));
 }
 
 static void sh_msiof_spi_write_fifo_8(struct sh_msiof_spi_priv *p,