[PATCH] dmaengine: mediatek: uart: synchronize completion callbacks

[James Hilliard <james.hilliard1@gmail.com>]

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.

Implement the hook using vchan_synchronize(). This lets clients finish
asynchronous cancellation before reusing callback state or freeing DMA
buffers. Keep the callback wait out of device_terminate_all so it can be
performed without locks acquired by the callback.

Fixes: 9135408c3ace ("dmaengine: mediatek: Add MediaTek UART APDMA support")
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
---
 drivers/dma/mediatek/mtk-uart-apdma.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/dma/mediatek/mtk-uart-apdma.c b/drivers/dma/mediatek/mtk-uart-apdma.c
index f74e9a328588..7583c287da5d 100644
--- a/drivers/dma/mediatek/mtk-uart-apdma.c
+++ b/drivers/dma/mediatek/mtk-uart-apdma.c
@@ -440,6 +440,13 @@ static int mtk_uart_apdma_terminate_all(struct dma_chan *chan)
 	return 0;
 }
 
+static void mtk_uart_apdma_synchronize(struct dma_chan *chan)
+{
+	struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
+
+	vchan_synchronize(&c->vc);
+}
+
 static int mtk_uart_apdma_device_pause(struct dma_chan *chan)
 {
 	struct mtk_chan *c = to_mtk_uart_apdma_chan(chan);
@@ -514,6 +521,7 @@ 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 = mtk_uart_apdma_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);

---
base-commit: 93f51579e7df248780214094418f205253383cc5
change-id: 20261021-submit-mtk-uart-dma-synchronize-v1-158c8303b574

Best regards,
--  
James Hilliard <james.hilliard1@gmail.com>