From 6e98921f6f2f1be03055bd7eb201c17761d40fc7 Mon Sep 17 00:00:00 2001 From: Akhil R Date: Fri, 15 Mar 2024 18:14:11 +0530 Subject: dmaengine: tegra186: Fix residual calculation [ 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 Reviewed-by: Jon Hunter Acked-by: Thierry Reding Link: https://lore.kernel.org/r/20240315124411.17582-1-akhilrajeev@nvidia.com Signed-off-by: Vinod Koul Signed-off-by: Sasha Levin --- 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 33b101001100..674cf6305283 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; -- cgit v1.2.3