dmaengine: tegra186: Fix residual calculation
[ Upstream commit30f0ced997
] 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:ee17028009
("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>
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@ -746,6 +746,9 @@ static int tegra_dma_get_residual(struct tegra_dma_channel *tdc)
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bytes_xfer = dma_desc->bytes_xfer +
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sg_req[dma_desc->sg_idx].len - (wcount * 4);
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if (dma_desc->bytes_req == bytes_xfer)
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return 0;
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residual = dma_desc->bytes_req - (bytes_xfer % dma_desc->bytes_req);
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return residual;
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