[PATCH v3 2/2] dmaengine: mediatek: uart: synchronize completion callbacks

[James Hilliard]

Terminating a UART APDMA channel waits for its interrupt handler, but
completion callbacks run in the virt-dma tasklet. A callback already
removed from desc_completed can still be running after termination
returns. With no device_synchronize hook, dmaengine_synchronize() does
not wait for that callback either.

Use vchan_dma_synchronize() as the UART APDMA device_synchronize callback
so clients can wait for completion callbacks before reusing callback
state or freeing DMA buffers. Keep the callback wait separate from
device_terminate_all so it can run without locks acquired by the callback.

Fixes: 9135408c3ace ("dmaengine: mediatek: Add MediaTek UART APDMA support")
Suggested-by: Frank Li <Frank.li@xxxxxxxxxxx>
Signed-off-by: James Hilliard <james.hilliard1@xxxxxxxxx>
---
 drivers/dma/mediatek/mtk-uart-apdma.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/dma/mediatek/mtk-uart-apdma.c b/drivers/dma/mediatek/mtk-uart-apdma.c
index f74e9a328588..6bc4f20d8b06 100644
--- a/drivers/dma/mediatek/mtk-uart-apdma.c
+++ b/drivers/dma/mediatek/mtk-uart-apdma.c
@@ -514,6 +514,7 @@ static int mtk_uart_apdma_probe(struct platform_device *pdev)
 	mtkd->ddev.device_config = mtk_uart_apdma_slave_config;
 	mtkd->ddev.device_pause = mtk_uart_apdma_device_pause;
 	mtkd->ddev.device_terminate_all = mtk_uart_apdma_terminate_all;
+	mtkd->ddev.device_synchronize = vchan_dma_synchronize;
 	mtkd->ddev.src_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
 	mtkd->ddev.dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE);
 	mtkd->ddev.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV);

-- 
2.53.0