amd-xgbe: Use wmb before updating current descriptor count
The code currently uses the lightweight dma_wmb barrier before updating the current descriptor count. Under heavy load, the Tx cleanup routine was seeing the updated current descriptor count before the updated descriptor information. As a result, the Tx descriptor was being cleaned up before it was used because it was not "owned" by the hardware yet, resulting in a Tx queue hang. Using the wmb barrier insures that the descriptor is updated before the descriptor counter preventing the Tx queue hang. For extra insurance, the Tx cleanup routine is changed to grab the current decriptor count on entry and uses that initial value in the processing loop rather than trying to chase the current value. Signed-off-by: NTom Lendacky <thomas.lendacky@amd.com> Tested-by: NChristoffer Dall <christoffer.dall@linaro.org> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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