6.8-stable review patch. If anyone has any objections, please let me know.
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From: Akhil R akhilrajeev@nvidia.com
[ Upstream commit 30f0ced9971b2d8c8c24ae75786f9079489a012d ]
The existing residual calculation returns an incorrect value when bytes_xfer == bytes_req. This scenario occurs particularly with drivers like UART where DMA is scheduled for maximum number of bytes and is terminated when the bytes inflow stops. At higher baud rates, it could request the tx_status while there is no bytes left to transfer. This will lead to incorrect residual being set. Hence return residual as '0' when bytes transferred equals to the bytes requested.
Fixes: ee17028009d4 ("dmaengine: tegra: Add tegra gpcdma driver") Signed-off-by: Akhil R akhilrajeev@nvidia.com Reviewed-by: Jon Hunter jonathanh@nvidia.com Acked-by: Thierry Reding treding@nvidia.com Link: https://lore.kernel.org/r/20240315124411.17582-1-akhilrajeev@nvidia.com Signed-off-by: Vinod Koul vkoul@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/dma/tegra186-gpc-dma.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/dma/tegra186-gpc-dma.c b/drivers/dma/tegra186-gpc-dma.c index 88547a23825b1..3642508e88bb2 100644 --- a/drivers/dma/tegra186-gpc-dma.c +++ b/drivers/dma/tegra186-gpc-dma.c @@ -746,6 +746,9 @@ static int tegra_dma_get_residual(struct tegra_dma_channel *tdc) bytes_xfer = dma_desc->bytes_xfer + sg_req[dma_desc->sg_idx].len - (wcount * 4);
+ if (dma_desc->bytes_req == bytes_xfer) + return 0; + residual = dma_desc->bytes_req - (bytes_xfer % dma_desc->bytes_req);
return residual;