Re: [PATCH V2 3/9] spi: bcm2835aux: use BCM2835_AUX_SPI_STAT_RX_LVL

[Stefan Wahren <stefan.wahren@xxxxxxxx>]

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@xxxxxxxxxxxxxxxx:
> From: Martin Sperl <kernel@xxxxxxxxxxxxxxxx>
>
> 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