tty: atmel_serial: use single DMA mapping for TX

dma_map_single() provides much easier interface for simple mappings as
used for TX in atmel_serial. So switch to that, removing all the s-g
unnecessary handling.

Note that it is not easy (maybe impossible) to use kfifo_dma_* API for
atmel's serial purposes. It handles DMA very specially.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: Richard Genoud <richard.genoud@gmail.com>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20240405060826.2521-14-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 5bb5e4303754bfd25bcb0728c21911a7c549f978..69ec80ffc97b0441ec8a607ea4de59a7f10011c0 100644 (file)
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -132,7 +132,7 @@ struct atmel_uart_port {
        struct dma_async_tx_descriptor  *desc_rx;
        dma_cookie_t                    cookie_tx;
        dma_cookie_t                    cookie_rx;
-       struct scatterlist              sg_tx;
+       dma_addr_t                      tx_phys;
        struct scatterlist              sg_rx;
        struct tasklet_struct   tasklet_rx;
        struct tasklet_struct   tasklet_tx;
@@ -904,8 +904,8 @@ static void atmel_release_tx_dma(struct uart_port *port)
        if (chan) {
                dmaengine_terminate_all(chan);
                dma_release_channel(chan);
-               dma_unmap_sg(port->dev, &atmel_port->sg_tx, 1,
-                               DMA_TO_DEVICE);
+               dma_unmap_single(port->dev, atmel_port->tx_phys,
+                                UART_XMIT_SIZE, DMA_TO_DEVICE);
        }
 
        atmel_port->desc_tx = NULL;
@@ -922,7 +922,7 @@ static void atmel_tx_dma(struct uart_port *port)
        struct tty_port *tport = &port->state->port;
        struct dma_chan *chan = atmel_port->chan_tx;
        struct dma_async_tx_descriptor *desc;
-       struct scatterlist sgl[2], *sg, *sg_tx = &atmel_port->sg_tx;
+       struct scatterlist sgl[2], *sg;
        unsigned int tx_len, tail, part1_len, part2_len, sg_len;
        dma_addr_t phys_addr;
 
@@ -955,7 +955,7 @@ static void atmel_tx_dma(struct uart_port *port)
 
                sg_init_table(sgl, 2);
                sg_len = 0;
-               phys_addr = sg_dma_address(sg_tx) + tail;
+               phys_addr = atmel_port->tx_phys + tail;
                if (part1_len) {
                        sg = &sgl[sg_len++];
                        sg_dma_address(sg) = phys_addr;
@@ -987,7 +987,8 @@ static void atmel_tx_dma(struct uart_port *port)
                        return;
                }
 
-               dma_sync_sg_for_device(port->dev, sg_tx, 1, DMA_TO_DEVICE);
+               dma_sync_single_for_device(port->dev, atmel_port->tx_phys,
+                                          UART_XMIT_SIZE, DMA_TO_DEVICE);
 
                atmel_port->desc_tx = desc;
                desc->callback = atmel_complete_tx_dma;
@@ -1014,7 +1015,7 @@ static int atmel_prepare_tx_dma(struct uart_port *port)
        dma_cap_mask_t          mask;
        struct dma_slave_config config;
        struct dma_chan *chan;
-       int ret, nent;
+       int ret;
 
        dma_cap_zero(mask);
        dma_cap_set(DMA_SLAVE, mask);
@@ -1029,26 +1030,18 @@ static int atmel_prepare_tx_dma(struct uart_port *port)
                dma_chan_name(atmel_port->chan_tx));
 
        spin_lock_init(&atmel_port->lock_tx);
-       sg_init_table(&atmel_port->sg_tx, 1);
        /* UART circular tx buffer is an aligned page. */
        BUG_ON(!PAGE_ALIGNED(tport->xmit_buf));
-       sg_set_page(&atmel_port->sg_tx,
-                       virt_to_page(tport->xmit_buf),
-                       UART_XMIT_SIZE,
-                       offset_in_page(tport->xmit_buf));
-       nent = dma_map_sg(port->dev,
-                               &atmel_port->sg_tx,
-                               1,
-                               DMA_TO_DEVICE);
+       atmel_port->tx_phys = dma_map_single(port->dev, tport->xmit_buf,
+                                            UART_XMIT_SIZE, DMA_TO_DEVICE);
 
-       if (!nent) {
+       if (dma_mapping_error(port->dev, atmel_port->tx_phys)) {
                dev_dbg(port->dev, "need to release resource of dma\n");
                goto chan_err;
        } else {
-               dev_dbg(port->dev, "%s: mapped %d@%p to %pad\n", __func__,
-                       sg_dma_len(&atmel_port->sg_tx),
-                       tport->xmit_buf,
-                       &sg_dma_address(&atmel_port->sg_tx));
+               dev_dbg(port->dev, "%s: mapped %lu@%p to %pad\n", __func__,
+                       UART_XMIT_SIZE, tport->xmit_buf,
+                       &atmel_port->tx_phys);
        }
 
        /* Configure the slave DMA */