For quite some time we were chasing a bug which looked like a sudden
permanent failure of networking and mmc on some of our devices.
The bug was very sensitive to any software changes and even more to
any kernel debug options.
Finally we got a setup where the problem was reproducible with
CONFIG_DMA_API_DEBUG=y and it revealed the issue with the rx dma:
Lars was fast to find an explanation: according to the datasheet
bit 2 of the rx buffer descriptor entry has a different meaning in the
extended mode:
Address [2] of beginning of buffer, or
in extended buffer descriptor mode (DMA configuration register [28] = 1),
indicates a valid timestamp in the buffer descriptor entry.
The macb driver didn't mask this bit while getting an address and it
eventually caused a memory corruption and a dma failure.
The problem is resolved by explicitly clearing the problematic bit
if hw timestamping is used.
Fixes: 7b4296148066 ("net: macb: Add support for PTP timestamps in DMA descriptors") Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev> Co-developed-by: Lars-Peter Clausen <lars@metafoo.de> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de> Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com> Reviewed-by: Jacob Keller <jacob.e.keller@intel.com> Link: https://lore.kernel.org/r/20230412232144.770336-1-roman.gushchin@linux.dev Signed-off-by: Jakub Kicinski <kuba@kernel.org>