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| author |   Martin Sperl <kernel@martin.sperl.org> | 2019-03-30 09:31:00 +0000 |
|---|---|---|
| committer |   Mark Brown <broonie@kernel.org> | 2019-04-03 11:31:11 +0700 |
| commit | 73b114ee7db1750c0b535199fae383b109bd61d0 (patch) | |
| tree | 01076bca50c2a604f8a21ea5cb99d5ee90e556aa /drivers/spi/spi-bcm2835aux.c | |
| parent | spi: bcm2835aux: remove dangerous uncontrolled read of fifo (diff) | |
| download | linux-dev-73b114ee7db1750c0b535199fae383b109bd61d0.tar.xz linux-dev-73b114ee7db1750c0b535199fae383b109bd61d0.zip | |
spi: bcm2835aux: fix corruptions for longer spi transfers
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>
Diffstat (limited to 'drivers/spi/spi-bcm2835aux.c')
| -rw-r--r-- | drivers/spi/spi-bcm2835aux.c | 8 |
1 files 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 && |