[PATCH v2 1/8] serial: stm32: fix DMA initialization error handling

[Erwan Le Ray]

DMA initialization error handling is not properly implemented in the
driver.
Fix DMA initialization error handling by:
- moving TX DMA descriptor request error handling in a new dedicated
fallback_err label
- adding error handling to TX DMA descriptor submission
- adding error handling to RX DMA descriptor submission

This patch depends on '24832ca3ee85 ("tty: serial: stm32-usart: Remove set
but unused 'cookie' variables")' which unfortunately doesn't include a
"Fixes" tag.

Fixes: 3489187204eb ("serial: stm32: adding dma support")
Signed-off-by: Erwan Le Ray <erwan.le...@foss.st.com>
---
Changes in v2:
- delete DMA cookie variables removal from V1 patch as already done by a
previous patch
- update commit message as DMA cookie variables removal is no more
included in this patch

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index f4de32d3f2af..6248304a001f 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -383,17 +383,18 @@ static void stm32_transmit_chars_dma(struct uart_port 
*port)
                                           DMA_MEM_TO_DEV,
                                           DMA_PREP_INTERRUPT);
 
-       if (!desc) {
-               for (i = count; i > 0; i--)
-                       stm32_transmit_chars_pio(port);
-               return;
-       }
+       if (!desc)
+               goto fallback_err;
 
        desc->callback = stm32_tx_dma_complete;
        desc->callback_param = port;
 
        /* Push current DMA TX transaction in the pending queue */
-       dmaengine_submit(desc);
+       if (dma_submit_error(dmaengine_submit(desc))) {
+               /* dma no yet started, safe to free resources */
+               dmaengine_terminate_async(stm32port->tx_ch);
+               goto fallback_err;
+       }
 
        /* Issue pending DMA TX requests */
        dma_async_issue_pending(stm32port->tx_ch);
@@ -402,6 +403,11 @@ static void stm32_transmit_chars_dma(struct uart_port 
*port)
 
        xmit->tail = (xmit->tail + count) & (UART_XMIT_SIZE - 1);
        port->icount.tx += count;
+       return;
+
+fallback_err:
+       for (i = count; i > 0; i--)
+               stm32_transmit_chars_pio(port);
 }
 
 static void stm32_transmit_chars(struct uart_port *port)
@@ -1130,7 +1136,11 @@ static int stm32_of_dma_rx_probe(struct stm32_port 
*stm32port,
        desc->callback_param = NULL;
 
        /* Push current DMA transaction in the pending queue */
-       dmaengine_submit(desc);
+       ret = dma_submit_error(dmaengine_submit(desc));
+       if (ret) {
+               dmaengine_terminate_sync(stm32port->rx_ch);
+               goto config_err;
+       }
 
        /* Issue pending DMA requests */
        dma_async_issue_pending(stm32port->rx_ch);
-- 
2.17.1