[PATCH 6.19 327/342] dmaengine: xilinx: xilinx_dma: Fix unmasked residue subtraction

Greg Kroah-Hartman
2026-03-31T16:45:21Z

From: Marek Vasut <marex@nabladev.com>

[ Upstream commit c7d812e33f3e8ca0fa9eeabf71d1c7bc3acedc09 ]

The segment .control and .status fields both contain top bits which are
not part of the buffer size, the buffer size is located only in the bottom
max_buffer_len bits. To avoid interference from those top bits, mask out
the size using max_buffer_len first, and only then subtract the values.

Fixes: a575d0b4e663 ("dmaengine: xilinx_dma: Introduce xilinx_dma_get_residue")
Signed-off-by: Marek Vasut <marex@nabladev.com>
Link: https://patch.msgid.link/20260316222530.163815-1-marex@nabladev.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/dma/xilinx/xilinx_dma.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
index ccfcc2b801f82..7b24d0a18ea53 100644
--- a/drivers/dma/xilinx/xilinx_dma.c
+++ b/drivers/dma/xilinx/xilinx_dma.c
@@ -997,16 +997,16 @@ static u32 xilinx_dma_get_residue(struct xilinx_dma_chan *chan,
struct xilinx_cdma_tx_segment,
node);
cdma_hw = &cdma_seg->hw;
- residue += (cdma_hw->control - cdma_hw->status) &
- chan->xdev->max_buffer_len;
+ residue += (cdma_hw->control & chan->xdev->max_buffer_len) -
+ (cdma_hw->status & chan->xdev->max_buffer_len);
} else if (chan->xdev->dma_config->dmatype ==
XDMA_TYPE_AXIDMA) {
axidma_seg = list_entry(entry,
struct xilinx_axidma_tx_segment,
node);
axidma_hw = &axidma_seg->hw;
- residue += (axidma_hw->control - axidma_hw->status) &
- chan->xdev->max_buffer_len;
+ residue += (axidma_hw->control & chan->xdev->max_buffer_len) -
+ (axidma_hw->status & chan->xdev->max_buffer_len);
} else {
aximcdma_seg =
list_entry(entry,
@@ -1014,8 +1014,8 @@ static u32 xilinx_dma_get_residue(struct xilinx_dma_chan *chan,
node);
aximcdma_hw = &aximcdma_seg->hw;
residue +=
- (aximcdma_hw->control - aximcdma_hw->status) &
- chan->xdev->max_buffer_len;
+ (aximcdma_hw->control & chan->xdev->max_buffer_len) -
+ (aximcdma_hw->status & chan->xdev->max_buffer_len);
}
}

--
2.53.0