On Thu, Nov 10, 2022 at 07:31:34PM +0200, Yaron Micher wrote:
The rx descriptor list is in cached memory, and there may be multiple descriptors per cache-line. After reclaim_rx_buffers marks a descriptor as unused it does a cache flush, which causes the entire cache-line to be written to memory, which may override other descriptors in the same cache-line that the controller may have written to.
The fix skips freeing descriptors that are not the last in a cache-line, and if the freed descriptor is the last one in a cache-line, it marks all the descriptors in the cache-line as unused. This is similarly to what is done in drivers/net/fec_mxc.c
In my case this bug caused tftpboot to fail some times when other packets are sent to u-boot in addition to the ongoing tftp (e.g. ping). The driver would stop receiving new packets because it is waiting on a descriptor that is marked unused, when in reality the descriptor contains a new unprocessed packet but while freeing the previous buffer descriptor & flushing the cache, the driver accidentally marked the descriptor as unused.
Signed-off-by: Yaron Micher yaronm@hailo.ai
Applied to u-boot/master, thanks!