From 73b114ee7db1750c0b535199fae383b109bd61d0 Mon Sep 17 00:00:00 2001
From: Martin Sperl <kernel@martin.sperl.org>
Date: Sat, 30 Mar 2019 09:31:00 +0000
Subject: [PATCH] spi: bcm2835aux: fix corruptions for longer spi transfers
Git-commit: 73b114ee7db1750c0b535199fae383b109bd61d0
Patch-mainline: v5.2-rc1
References: bsc#1051510
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: 1ea29b39f4c812ec ("spi: bcm2835aux: add bcm2835 auxiliary spi device...")
Reported-by: Hubert Denkmair <h.denkmair@intence.de>
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/spi/spi-bcm2835aux.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
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 &&
--
2.16.4