serial: msm: check dma_map_sg() return value properly

The -next commit f8fef2fa419f (tty: msm_serial: use
dmaengine_prep_slave_sg()), switched to using dma_map_sg(). But the
return value of dma_map_sg() is special: it returns number of elements
mapped. And not a standard error value.

The commit also forgot to reset dma->tx_sg in case of this failure.

Fix both these mistakes.

Thanks to Marek who helped debugging this.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20240419080931.30949-1-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index ae7a8e3cf467acf3d46d8afd6a513f30bc4d081b..0a9c5219df88bf30ee9c48ef95cc487a038fab01 100644 (file)
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -499,15 +499,18 @@ static int msm_handle_tx_dma(struct msm_port *msm_port, unsigned int count)
        struct uart_port *port = &msm_port->uart;
        struct tty_port *tport = &port->state->port;
        struct msm_dma *dma = &msm_port->tx_dma;
+       unsigned int mapped;
        int ret;
        u32 val;
 
        sg_init_table(&dma->tx_sg, 1);
        kfifo_dma_out_prepare(&tport->xmit_fifo, &dma->tx_sg, 1, count);
 
-       ret = dma_map_sg(port->dev, &dma->tx_sg, 1, dma->dir);
-       if (ret)
-               return ret;
+       mapped = dma_map_sg(port->dev, &dma->tx_sg, 1, dma->dir);
+       if (!mapped) {
+               ret = -EIO;
+               goto zero_sg;
+       }
 
        dma->desc = dmaengine_prep_slave_sg(dma->chan, &dma->tx_sg, 1,
                                                DMA_MEM_TO_DEV,
@@ -548,6 +551,7 @@ static int msm_handle_tx_dma(struct msm_port *msm_port, unsigned int count)
        return 0;
 unmap:
        dma_unmap_sg(port->dev, &dma->tx_sg, 1, dma->dir);
+zero_sg:
        sg_init_table(&dma->tx_sg, 1);
        return ret;
 }