> > When DMA is used for TX and RX by serial driver, it should pass the > > DMA device pointer to DMA API instead of UART device pointer. DMA > > device should be used for DMA API because only the DMA device is aware > > of how the device connects to the memory. > > There might be an extra level of address translation due to a SMMU > > attached to the DMA device. When serial device pointer device is used > > for DMA API, the DMA API will have no clue of the SMMU attached to the > > DMA device. > > > > This patch is necessary to fix the SMMU page faults which is observed > > when a DMA(with SMMU enabled) is attached to UART for transfer. > > > > Signed-off-by: Tamseel Shams <m.shams@xxxxxxxxxxx> > > Signed-off-by: Ajay Kumar <ajaykumar.rs@xxxxxxxxxxx> > > --- > > Changes since v1: > > 1. Rebased the patch on "tty-next" branch of TTY driver tree > > > > Changes since v2: > > 1. Updated the commit message. > > 2. Changed the comment description > > > > drivers/tty/serial/samsung_tty.c | 62 > > +++++++++++++++++++++++++------- > > 1 file changed, 50 insertions(+), 12 deletions(-) > > > > diff --git a/drivers/tty/serial/samsung_tty.c > > b/drivers/tty/serial/samsung_tty.c > > index 9fbc61151c2e..7dd648cb7237 100644 > > --- a/drivers/tty/serial/samsung_tty.c > > +++ b/drivers/tty/serial/samsung_tty.c > > @@ -284,8 +284,13 @@ static void s3c24xx_serial_stop_tx(struct uart_port > *port) > > struct s3c24xx_uart_dma *dma = ourport->dma; > > struct circ_buf *xmit = &port->state->xmit; > > struct dma_tx_state state; > > + struct device *dma_map_ops_dev = ourport->port.dev; > > int count; > > > > + /* Null pointer check for "dma" and "dma->tx_chan" */ > > The comment is not useful. > I will remove these comments. > > + if (dma && dma->tx_chan) > > + dma_map_ops_dev = dma->tx_chan->device->dev; > > + > > if (!ourport->tx_enabled) > > return; > > > > @@ -305,7 +310,7 @@ static void s3c24xx_serial_stop_tx(struct uart_port > *port) > > dmaengine_pause(dma->tx_chan); > > dmaengine_tx_status(dma->tx_chan, dma->tx_cookie, &state); > > dmaengine_terminate_all(dma->tx_chan); > > - dma_sync_single_for_cpu(ourport->port.dev, > > + dma_sync_single_for_cpu(dma_map_ops_dev, > > dma->tx_transfer_addr, dma->tx_size, > DMA_TO_DEVICE); > > async_tx_ack(dma->tx_desc); > > count = dma->tx_bytes_requested - state.residue; @@ -331,14 > +336,19 > > @@ static void s3c24xx_serial_tx_dma_complete(void *args) > > struct circ_buf *xmit = &port->state->xmit; > > struct s3c24xx_uart_dma *dma = ourport->dma; > > struct dma_tx_state state; > > + struct device *dma_map_ops_dev = ourport->port.dev; > > unsigned long flags; > > int count; > > > > + /* Null pointer check for "dma" and "dma->tx_chan" */ > > + if (dma && dma->tx_chan) > > > What is the "else" here? How is it even possible? Why having this "if" > at all? > As mentioned in my reply (https://lkml.org/lkml/2021/6/23/6) to Robin's comments for patch version 2, I will be removing these "if" conditions, and directly assign DMA device pointers. > > + dma_map_ops_dev = dma->tx_chan->device->dev; > > + > > dmaengine_tx_status(dma->tx_chan, dma->tx_cookie, &state); > > count = dma->tx_bytes_requested - state.residue; > > async_tx_ack(dma->tx_desc); > > > > - dma_sync_single_for_cpu(ourport->port.dev, dma->tx_transfer_addr, > > + dma_sync_single_for_cpu(dma_map_ops_dev, dma->tx_transfer_addr, > > dma->tx_size, DMA_TO_DEVICE); > > > > spin_lock_irqsave(&port->lock, flags); @@ -436,6 +446,11 @@ static > > int s3c24xx_serial_start_tx_dma(struct s3c24xx_uart_port *ourport, > > struct uart_port *port = &ourport->port; > > struct circ_buf *xmit = &port->state->xmit; > > struct s3c24xx_uart_dma *dma = ourport->dma; > > + struct device *dma_map_ops_dev = ourport->port.dev; > > + > > + /* Null pointer check for "dma" and "dma->tx_chan" */ > > + if (dma && dma->tx_chan) > > + dma_map_ops_dev = dma->tx_chan->device->dev; > > > > if (ourport->tx_mode != S3C24XX_TX_DMA) > > enable_tx_dma(ourport); > > @@ -443,7 +458,7 @@ static int s3c24xx_serial_start_tx_dma(struct > s3c24xx_uart_port *ourport, > > dma->tx_size = count & ~(dma_get_cache_alignment() - 1); > > dma->tx_transfer_addr = dma->tx_addr + xmit->tail; > > > > - dma_sync_single_for_device(ourport->port.dev, dma- > >tx_transfer_addr, > > + dma_sync_single_for_device(dma_map_ops_dev, dma- > >tx_transfer_addr, > > dma->tx_size, DMA_TO_DEVICE); > > > > dma->tx_desc = dmaengine_prep_slave_single(dma->tx_chan, > > @@ -510,12 +525,17 @@ static void s3c24xx_uart_copy_rx_to_tty(struct > s3c24xx_uart_port *ourport, > > struct tty_port *tty, int count) > > { > > struct s3c24xx_uart_dma *dma = ourport->dma; > > + struct device *dma_map_ops_dev = ourport->port.dev; > > int copied; > > > > + /* Null pointer check for "dma" and "dma->rx_chan" */ > > + if (dma && dma->rx_chan) > > + dma_map_ops_dev = dma->rx_chan->device->dev; > > + > > if (!count) > > return; > > > > - dma_sync_single_for_cpu(ourport->port.dev, dma->rx_addr, > > + dma_sync_single_for_cpu(dma_map_ops_dev, dma->rx_addr, > > dma->rx_size, DMA_FROM_DEVICE); > > > > ourport->port.icount.rx += count; > > @@ -635,8 +655,13 @@ static void s3c24xx_serial_rx_dma_complete(void > > *args) static void s3c64xx_start_rx_dma(struct s3c24xx_uart_port > > *ourport) { > > struct s3c24xx_uart_dma *dma = ourport->dma; > > + struct device *dma_map_ops_dev = ourport->port.dev; > > + > > + /* Null pointer check for "dma" and "dma->rx_chan" */ > > + if (dma && dma->rx_chan) > > + dma_map_ops_dev = dma->rx_chan->device->dev; > > > > - dma_sync_single_for_device(ourport->port.dev, dma->rx_addr, > > + dma_sync_single_for_device(dma_map_ops_dev, dma->rx_addr, > > dma->rx_size, DMA_FROM_DEVICE); > > > > dma->rx_desc = dmaengine_prep_slave_single(dma->rx_chan, > > @@ -1045,6 +1070,7 @@ 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; > > + struct device *dma_map_ops_dev = p->port.dev; > > int ret; > > > > /* Default slave configuration parameters */ @@ -1102,18 +1128,25 > @@ > > static int s3c24xx_serial_request_dma(struct s3c24xx_uart_port *p) > > goto err_release_tx; > > } > > > > - dma->rx_addr = dma_map_single(p->port.dev, dma->rx_buf, > > + /* Null pointer check for "dma" and "dma->rx_chan" */ > > + if (dma && dma->rx_chan) > > + dma_map_ops_dev = dma->rx_chan->device->dev; > > + > > + dma->rx_addr = dma_map_single(dma_map_ops_dev, dma->rx_buf, > > dma->rx_size, DMA_FROM_DEVICE); > > - if (dma_mapping_error(p->port.dev, dma->rx_addr)) { > > + if (dma_mapping_error(dma_map_ops_dev, dma->rx_addr)) { > > reason = "DMA mapping error for RX buffer"; > > ret = -EIO; > > goto err_free_rx; > > } > > > > + /* Null pointer check for "dma" and "dma->tx_chan" */ > > + if (dma && dma->tx_chan) > > + dma_map_ops_dev = dma->tx_chan->device->dev; > > /* TX buffer */ > > - dma->tx_addr = dma_map_single(p->port.dev, p->port.state->xmit.buf, > > + dma->tx_addr = dma_map_single(dma_map_ops_dev, > > +p->port.state->xmit.buf, > > UART_XMIT_SIZE, DMA_TO_DEVICE); > > - if (dma_mapping_error(p->port.dev, dma->tx_addr)) { > > + if (dma_mapping_error(dma_map_ops_dev, dma->tx_addr)) { > > reason = "DMA mapping error for TX buffer"; > > ret = -EIO; > > goto err_unmap_rx; > > @@ -1122,7 +1155,9 @@ static int s3c24xx_serial_request_dma(struct > s3c24xx_uart_port *p) > > return 0; > > > > err_unmap_rx: > > - dma_unmap_single(p->port.dev, dma->rx_addr, dma->rx_size, > > + if (dma->rx_chan) > > + dma_map_ops_dev = dma->rx_chan->device->dev; > > + dma_unmap_single(dma_map_ops_dev, dma->rx_addr, dma->rx_size, > > DMA_FROM_DEVICE); > > err_free_rx: > > kfree(dma->rx_buf); > > @@ -1139,10 +1174,12 @@ static int s3c24xx_serial_request_dma(struct > > s3c24xx_uart_port *p) static void s3c24xx_serial_release_dma(struct > > s3c24xx_uart_port *p) { > > struct s3c24xx_uart_dma *dma = p->dma; > > + struct device *dma_map_ops_dev = p->port.dev; > > > > if (dma->rx_chan) { > > + dma_map_ops_dev = dma->rx_chan->device->dev; > > dmaengine_terminate_all(dma->rx_chan); > > - dma_unmap_single(p->port.dev, dma->rx_addr, > > + dma_unmap_single(dma_map_ops_dev, dma->rx_addr, > > dma->rx_size, DMA_FROM_DEVICE); > > kfree(dma->rx_buf); > > dma_release_channel(dma->rx_chan); > > @@ -1150,8 +1187,9 @@ static void s3c24xx_serial_release_dma(struct > s3c24xx_uart_port *p) > > } > > > > if (dma->tx_chan) { > > + dma_map_ops_dev = dma->tx_chan->device->dev; > > dmaengine_terminate_all(dma->tx_chan); > > - dma_unmap_single(p->port.dev, dma->tx_addr, > > + dma_unmap_single(dma_map_ops_dev, dma->tx_addr, > > UART_XMIT_SIZE, DMA_TO_DEVICE); > > dma_release_channel(dma->tx_chan); > > dma->tx_chan = NULL; > > > > > Best regards, > Krzysztof Thanks & Regards, Tamseel Shams
