serial: 8250: Validate dmaengine rx chan meets requirements

8250 dma support requires the dmaengine driver support error-free
pause/terminate and better-than-descriptor residue granularity. Query
slave caps to determine if necessary commands/properties are supported;
disable dma if not.

Note this means dmaengine driver must support slave caps reporting
as well.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index 78259d3..cf7a2e3 100644 (file)
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -158,6 +158,8 @@ int serial8250_request_dma(struct uart_8250_port *p)
 {
        struct uart_8250_dma    *dma = p->dma;
        dma_cap_mask_t          mask;
+       struct dma_slave_caps   caps;
+       int                     ret;
 
        /* Default slave configuration parameters */
        dma->rxconf.direction           = DMA_DEV_TO_MEM;
@@ -178,6 +180,16 @@ int serial8250_request_dma(struct uart_8250_port *p)
        if (!dma->rxchan)
                return -ENODEV;
 
+       /* 8250 rx dma requires dmaengine driver to support pause/terminate */
+       ret = dma_get_slave_caps(dma->rxchan, &caps);
+       if (ret)
+               goto release_rx;
+       if (!caps.cmd_pause || !caps.cmd_terminate ||
+           caps.residue_granularity == DMA_RESIDUE_GRANULARITY_DESCRIPTOR) {
+               ret = -EINVAL;
+               goto release_rx;
+       }
+
        dmaengine_slave_config(dma->rxchan, &dma->rxconf);
 
        /* Get a channel for TX */
@@ -185,8 +197,8 @@ int serial8250_request_dma(struct uart_8250_port *p)
                                                       dma->fn, dma->tx_param,
                                                       p->port.dev, "tx");
        if (!dma->txchan) {
-               dma_release_channel(dma->rxchan);
-               return -ENODEV;
+               ret = -ENODEV;
+               goto release_rx;
        }
 
        dmaengine_slave_config(dma->txchan, &dma->txconf);
@@ -197,8 +209,10 @@ int serial8250_request_dma(struct uart_8250_port *p)
 
        dma->rx_buf = dma_alloc_coherent(dma->rxchan->device->dev, dma->rx_size,
                                        &dma->rx_addr, GFP_KERNEL);
-       if (!dma->rx_buf)
+       if (!dma->rx_buf) {
+               ret = -ENOMEM;
                goto err;
+       }
 
        /* TX buffer */
        dma->tx_addr = dma_map_single(dma->txchan->device->dev,
@@ -208,6 +222,7 @@ int serial8250_request_dma(struct uart_8250_port *p)
        if (dma_mapping_error(dma->txchan->device->dev, dma->tx_addr)) {
                dma_free_coherent(dma->rxchan->device->dev, dma->rx_size,
                                  dma->rx_buf, dma->rx_addr);
+               ret = -ENOMEM;
                goto err;
        }
 
@@ -215,10 +230,10 @@ int serial8250_request_dma(struct uart_8250_port *p)
 
        return 0;
 err:
-       dma_release_channel(dma->rxchan);
        dma_release_channel(dma->txchan);
-
-       return -ENOMEM;
+release_rx:
+       dma_release_channel(dma->rxchan);
+       return ret;
 }
 EXPORT_SYMBOL_GPL(serial8250_request_dma);