diff mbox series

[V2,3/9] spi: bcm2835aux: use BCM2835_AUX_SPI_STAT_RX_LVL

Message ID 20190324175002.28969-4-kernel@martin.sperl.org (mailing list archive)
State New, archived
Headers show
Series spi: bcm2835aux: bug fixes and improvements | expand

Commit Message

Martin Sperl March 24, 2019, 5:49 p.m. UTC 
From: Martin Sperl <kernel@martin.sperl.org>

On long running tests with a mcp2517fd can controller it showed that
on rare occations the data read shows corruptions for longer spi transfers.

Example of a 22 byte transfer:

expected (as captured on logic analyzer):
FF FF 78 00 00 00 08 06 00 00 91 20 77 56 84 85 86 87 88 89 8a 8b

read by the driver:
FF FF 78 00 00 00 08 06 00 00 91 20 77 56 84 88 89 8a 00 00 8b 9b

To fix this use BCM2835_AUX_SPI_STAT_RX_LVL to determine when we may
read data from the fifo reliably without any corruption.

Surprisingly the only values ever empirically read in
BCM2835_AUX_SPI_STAT_RX_LVL are 0x00, 0x10, 0x20 and 0x30.
So whenever the mask is not 0 we can read from the fifo in a safe manner.

The patch has now been tested intensively and we are no longer
able to reproduce the "RX" issue any longer.

Fixes: 1ea29b39f4c812ece2f936065a0a3d6fe44a263e

Reported-by: Hubert Denkmair <h.denkmair@intence.de>
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
---
 drivers/spi/spi-bcm2835aux.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--
2.11.0

Comments

Stefan Wahren March 25, 2019, 9:52 a.m. UTC | #1 
Hi Martin,

here is my suggestion for a subject:

spi: bcm2835aux: fix corruptions for longer spi transfers

Am 24.03.19 um 18:49 schrieb kernel@martin.sperl.org:
> From: Martin Sperl <kernel@martin.sperl.org>
>
> On long running tests with a mcp2517fd can controller it showed that
> on rare occations the data read shows corruptions for longer spi transfers.
>
> Example of a 22 byte transfer:
>
> expected (as captured on logic analyzer):
> FF FF 78 00 00 00 08 06 00 00 91 20 77 56 84 85 86 87 88 89 8a 8b
>
> read by the driver:
> FF FF 78 00 00 00 08 06 00 00 91 20 77 56 84 88 89 8a 00 00 8b 9b
>
> To fix this use BCM2835_AUX_SPI_STAT_RX_LVL to determine when we may
> read data from the fifo reliably without any corruption.
>
> Surprisingly the only values ever empirically read in
> BCM2835_AUX_SPI_STAT_RX_LVL are 0x00, 0x10, 0x20 and 0x30.
> So whenever the mask is not 0 we can read from the fifo in a safe manner.
>
> The patch has now been tested intensively and we are no longer
> able to reproduce the "RX" issue any longer.
>
> Fixes: 1ea29b39f4c812ece2f936065a0a3d6fe44a263e

Please use a proper fixes tages in all of your patches. Doesn't
checkpatch.pl complain about it?

Thanks Stefan
diff mbox series

Patch

diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c
index 0838dbda57c7..d9e62f717a45 100644
--- a/drivers/spi/spi-bcm2835aux.c
+++ b/drivers/spi/spi-bcm2835aux.c
@@ -180,12 +180,12 @@  static void bcm2835aux_spi_reset_hw(struct bcm2835aux_spi *bs)

 static void bcm2835aux_spi_transfer_helper(struct bcm2835aux_spi *bs)
 {
+	u32 stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT);
+
 	/* check if we have data to read */
-	while (bs->rx_len &&
-	       (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
-		  BCM2835_AUX_SPI_STAT_RX_EMPTY))) {
+	for (; bs->rx_len && (stat & BCM2835_AUX_SPI_STAT_RX_LVL);
+	     stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT))
 		bcm2835aux_rd_fifo(bs);
-	}

 	/* check if we have data to write */
 	while (bs->tx_len &&