[PATCH AUTOSEL for 4.14 30/97] spi: sh-msiof: Fix timeout failures for TX-only DMA transfers

Sasha Levin
2018-03-19T15:55:19Z

From: Geert Uytterhoeven <geert+renesas@glider.be>

[ Upstream commit 89434c3c35081439627baa2225622d5bd12242fe ]

When using RX (with or without TX), the DMA interrupt triggers
completion when the RX FIFO has been emptied, i.e. after the full
transfer has finished.

However, when using TX without RX, the DMA interrupt triggers completion
as soon as the DMA engine has filled the TX FIFO, i.e. before the full
transfer has finished. Then sh_msiof_modify_ctr_wait() will spin until
the transfer has really finished and the TFSE bit is cleared, for at
most 1 ms. For slow speeds and/or large transfers, this may cause
timeouts and transfer failures:

spi_sh_msiof e6e10000.spi: failed to shut down hardware
74x164 spi2.0: SPI transfer failed: -110
spi_master spi2: failed to transfer one message from queue
74x164 spi2.0: Failed writing: -110

Fix this by waiting explicitly until the TX FIFO has been emptied.

Based on a patch in the BSP by Hiromitsu Yamasaki.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
drivers/spi/spi-sh-msiof.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-sh-msiof.c b/drivers/spi/spi-sh-msiof.c
index 837bb95eea62..ddd4cf4baee7 100644
--- a/drivers/spi/spi-sh-msiof.c
+++ b/drivers/spi/spi-sh-msiof.c
@@ -784,11 +784,21 @@ static int sh_msiof_dma_once(struct sh_msiof_spi_priv *p, const void *tx,
goto stop_dma;
}

- /* wait for tx fifo to be emptied / rx fifo to be filled */
+ /* wait for tx/rx DMA completion */
ret = sh_msiof_wait_for_completion(p);
if (ret)
goto stop_reset;

+ if (!rx) {
+ reinit_completion(&p->done);
+ sh_msiof_write(p, IER, IER_TEOFE);
+
+ /* wait for tx fifo to be emptied */
+ ret = sh_msiof_wait_for_completion(p);
+ if (ret)
+ goto stop_reset;
+ }
+
/* clear status bits */
sh_msiof_reset_str(p);

--
2.14.1