@@ -856,6 +856,8 @@ static void s3c24xx_serial_break_ctl(struct uart_port *port, int break_state)
static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
{
struct s3c24xx_uart_dma *dma = p->dma;
+ struct dma_slave_caps dma_caps;
+ const char *reason = NULL;
int ret;
/* Default slave configuration parameters */
@@ -871,17 +873,37 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
dma->rx_chan = dma_request_chan(p->port.dev, "rx");
- if (IS_ERR(dma->rx_chan))
- return PTR_ERR(dma->rx_chan);
+ if (IS_ERR(dma->rx_chan)) {
+ reason = "DMA RX channel request failed";
+ ret = PTR_ERR(dma->rx_chan);
+ goto err_warn;
+ }
+
+ ret = dma_get_slave_caps(dma->rx_chan, &dma_caps);
+ if (ret < 0 ||
+ dma_caps.residue_granularity < DMA_RESIDUE_GRANULARITY_BURST) {
+ reason = "insufficient DMA RX engine capabilities";
+ ret = -EOPNOTSUPP;
+ goto err_release_rx;
+ }
dmaengine_slave_config(dma->rx_chan, &dma->rx_conf);
dma->tx_chan = dma_request_chan(p->port.dev, "tx");
if (IS_ERR(dma->tx_chan)) {
+ reason = "DMA TX channel request failed";
ret = PTR_ERR(dma->tx_chan);
goto err_release_rx;
}
+ ret = dma_get_slave_caps(dma->tx_chan, &dma_caps);
+ if (ret < 0 ||
+ dma_caps.residue_granularity < DMA_RESIDUE_GRANULARITY_BURST) {
+ reason = "insufficient DMA TX engine capabilities";
+ ret = -EOPNOTSUPP;
+ goto err_release_tx;
+ }
+
dmaengine_slave_config(dma->tx_chan, &dma->tx_conf);
/* RX buffer */
@@ -896,6 +918,7 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
dma->rx_addr = dma_map_single(p->port.dev, dma->rx_buf,
dma->rx_size, DMA_FROM_DEVICE);
if (dma_mapping_error(p->port.dev, dma->rx_addr)) {
+ reason = "DMA mapping error for RX buffer";
ret = -EIO;
goto err_free_rx;
}
@@ -904,6 +927,7 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
dma->tx_addr = dma_map_single(p->port.dev, p->port.state->xmit.buf,
UART_XMIT_SIZE, DMA_TO_DEVICE);
if (dma_mapping_error(p->port.dev, dma->tx_addr)) {
+ reason = "DMA mapping error for TX buffer";
ret = -EIO;
goto err_unmap_rx;
}
@@ -919,6 +943,9 @@ static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p)
dma_release_channel(dma->tx_chan);
err_release_rx:
dma_release_channel(dma->rx_chan);
+err_warn:
+ if (reason)
+ dev_warn(p->port.dev, "%s, DMA will not be used\n", reason);
return ret;
}
@@ -1037,8 +1064,6 @@ static int s3c64xx_serial_startup(struct uart_port *port)
if (ourport->dma) {
ret = s3c24xx_serial_request_dma(ourport);
if (ret < 0) {
- dev_warn(port->dev,
- "DMA request failed, DMA will not be used\n");
devm_kfree(port->dev, ourport->dma);
ourport->dma = NULL;
}
DMA engine driver might not always provide all the features needed by serial driver to properly operate in DMA mode, so check that before selecting DMA mode. Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> --- v2: - added warnings with exact reason for not using DMA mode --- drivers/tty/serial/samsung.c | 33 +++++++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-) -- 2.17.0 -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html