amba-pl011​/dma: Add check for the residue in DMA callback

In DMA-operated uart, I found that rx data can be taken by the UART
interrupts during the DMA irq handler. pl011_int is occurred just
before it goes inside spin_lock_irq. When it returns to the callback,
DMA buffer already has been flushed. Then, pl011_dma_rx_chars gets
invalid data. So I add check for the residue as the patch bellow.

Signed-off-by: Chanho Min <chanho.min@lge.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 16 insertions, 1 deletions

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 6800f5f26241..cc3ea066c43a 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -827,7 +827,12 @@ static void pl011_dma_rx_callback(void *data)
 {
         struct uart_amba_port *uap = data;
         struct pl011_dmarx_data *dmarx = &uap->dmarx;
+        struct dma_chan *rxchan = dmarx->chan;
         bool lastbuf = dmarx->use_buf_b;
+        struct pl011_sgbuf *sgbuf = dmarx->use_buf_b ?
+                &dmarx->sgbuf_b : &dmarx->sgbuf_a;
+        size_t pending;
+        struct dma_tx_state state;
         int ret;
 
         /*
@@ -838,11 +843,21 @@ static void pl011_dma_rx_callback(void *data)
          * we immediately trigger the next DMA job.
          */
         spin_lock_irq(&uap->port.lock);
+        /*
+         * Rx data can be taken by the UART interrupts during
+         * the DMA irq handler. So we check the residue here.
+         */
+        rxchan->device->device_tx_status(rxchan, dmarx->cookie, &state);
+        pending = sgbuf->sg.length - state.residue;
+        BUG_ON(pending > PL011_DMA_BUFFER_SIZE);
+        /* Then we terminate the transfer - we now know our residue */
+        dmaengine_terminate_all(rxchan);
+
         uap->dmarx.running = false;
         dmarx->use_buf_b = !lastbuf;
         ret = pl011_dma_rx_trigger_dma(uap);
 
-        pl011_dma_rx_chars(uap, PL011_DMA_BUFFER_SIZE, lastbuf, false);
+        pl011_dma_rx_chars(uap, pending, lastbuf, false);
         spin_unlock_irq(&uap->port.lock);
         /*
          * Do this check after we picked the DMA chars so we don't