serial: amba-pl011: synchronize DMA teardown

[ Upstream commit 4409154 ]

dmaengine_terminate_all() does not wait for a running callback, so the TX
callback can still touch the TX buffer after it is freed. The RX poll
timer reads the RX buffers without the port lock.

Switch to dmaengine_terminate_sync() and delete the RX timer before
freeing the buffers.

Fixes: ead76f3 ("ARM: 6763/1: pl011: add optional RX DMA to PL011 v2")
Cc: stable <stable@kernel.org>
Assisted-by: Codex:gpt-5.6
Signed-off-by: Fan Wu <fanwu01@zju.edu.cn>
Link: https://patch.msgid.link/20260731085915.326775-4-fanwu01@zju.edu.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ changed upstream's `timer_delete_sync()` deletion to match this tree's `del_timer_sync()` spelling at the old call site ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Fan Wu

drivers/tty/serial/amba-pl011.c

@@ -1198,7 +1198,7 @@ static void pl011_dma_shutdown(struct uart_amba_port *uap)
 
 	if (uap->using_tx_dma) {
 		/* In theory, this should already be done by pl011_dma_flush_buffer */
-		dmaengine_terminate_all(uap->dmatx.chan);
+		dmaengine_terminate_sync(uap->dmatx.chan);
 		if (uap->dmatx.queued) {
 			dma_unmap_single(uap->dmatx.chan->device->dev,
 					 uap->dmatx.dma, uap->dmatx.len,
@@ -1211,12 +1211,12 @@ static void pl011_dma_shutdown(struct uart_amba_port *uap)
 	}
 
 	if (uap->using_rx_dma) {
-		dmaengine_terminate_all(uap->dmarx.chan);
+		if (uap->dmarx.poll_rate)
+			timer_delete_sync(&uap->dmarx.timer);
+		dmaengine_terminate_sync(uap->dmarx.chan);
 		/* Clean up the RX DMA */
 		pl011_dmabuf_free(uap->dmarx.chan, &uap->dmarx.dbuf_a, DMA_FROM_DEVICE);
 		pl011_dmabuf_free(uap->dmarx.chan, &uap->dmarx.dbuf_b, DMA_FROM_DEVICE);
-		if (uap->dmarx.poll_rate)
-			del_timer_sync(&uap->dmarx.timer);
 		uap->using_rx_dma = false;
 	}
 }