From 79904420b7be91d6aa84cbfa293f17545d9d5c49 Mon Sep 17 00:00:00 2001 From: Geert Uytterhoeven Date: Fri, 21 Aug 2015 20:02:42 +0200 Subject: [PATCH 1/1] serial: sh-sci: Switch to dma_map_single() for DMA transmission Simplify the DMA transmit code by using dma_map_single() instead of constantly modifying the single-entry scatterlist to match what's currently being transmitted. Signed-off-by: Geert Uytterhoeven Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/sh-sci.c | 50 +++++++++++++++---------------------- 1 file changed, 20 insertions(+), 30 deletions(-) diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index cb35c88645bb..5a528b898505 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -109,8 +109,8 @@ struct sci_port { dma_cookie_t cookie_tx; dma_cookie_t cookie_rx[2]; dma_cookie_t active_rx; - struct scatterlist sg_tx; - unsigned int sg_len_tx; + dma_addr_t tx_dma_addr; + unsigned int tx_dma_len; struct scatterlist sg_rx[2]; size_t buf_len_rx; struct sh_dmae_slave param_tx; @@ -1280,10 +1280,10 @@ static void sci_dma_tx_complete(void *arg) spin_lock_irqsave(&port->lock, flags); - xmit->tail += sg_dma_len(&s->sg_tx); + xmit->tail += s->tx_dma_len; xmit->tail &= UART_XMIT_SIZE - 1; - port->icount.tx += sg_dma_len(&s->sg_tx); + port->icount.tx += s->tx_dma_len; async_tx_ack(s->desc_tx); s->desc_tx = NULL; @@ -1494,7 +1494,7 @@ static void work_fn_tx(struct work_struct *work) struct dma_chan *chan = s->chan_tx; struct uart_port *port = &s->port; struct circ_buf *xmit = &port->state->xmit; - struct scatterlist *sg = &s->sg_tx; + dma_addr_t buf; /* * DMA is idle now. @@ -1504,19 +1504,15 @@ static void work_fn_tx(struct work_struct *work) * consistent xmit buffer state. */ spin_lock_irq(&port->lock); - sg->offset = xmit->tail & (UART_XMIT_SIZE - 1); - sg_dma_address(sg) = (sg_dma_address(sg) & ~(UART_XMIT_SIZE - 1)) + - sg->offset; - sg_dma_len(sg) = min_t(unsigned int, + buf = s->tx_dma_addr + (xmit->tail & (UART_XMIT_SIZE - 1)); + s->tx_dma_len = min_t(unsigned int, CIRC_CNT(xmit->head, xmit->tail, UART_XMIT_SIZE), CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE)); spin_unlock_irq(&port->lock); - BUG_ON(!sg_dma_len(sg)); - - desc = dmaengine_prep_slave_sg(chan, - sg, s->sg_len_tx, DMA_MEM_TO_DEV, - DMA_PREP_INTERRUPT | DMA_CTRL_ACK); + desc = dmaengine_prep_slave_single(chan, buf, s->tx_dma_len, + DMA_MEM_TO_DEV, + DMA_PREP_INTERRUPT | DMA_CTRL_ACK); if (!desc) { dev_warn(port->dev, "Failed preparing Tx DMA descriptor\n"); /* switch to PIO */ @@ -1524,7 +1520,8 @@ static void work_fn_tx(struct work_struct *work) return; } - dma_sync_sg_for_device(chan->device->dev, sg, 1, DMA_TO_DEVICE); + dma_sync_single_for_device(chan->device->dev, buf, s->tx_dma_len, + DMA_TO_DEVICE); spin_lock_irq(&port->lock); s->desc_tx = desc; @@ -1680,7 +1677,6 @@ static void sci_request_dma(struct uart_port *port) struct sh_dmae_slave *param; struct dma_chan *chan; dma_cap_mask_t mask; - int nent; dev_dbg(port->dev, "%s: port %d\n", __func__, port->line); @@ -1700,27 +1696,21 @@ static void sci_request_dma(struct uart_port *port) dev_dbg(port->dev, "%s: TX: got channel %p\n", __func__, chan); if (chan) { s->chan_tx = chan; - sg_init_table(&s->sg_tx, 1); /* UART circular tx buffer is an aligned page. */ - BUG_ON((uintptr_t)port->state->xmit.buf & ~PAGE_MASK); - sg_set_page(&s->sg_tx, virt_to_page(port->state->xmit.buf), - UART_XMIT_SIZE, - (uintptr_t)port->state->xmit.buf & ~PAGE_MASK); - nent = dma_map_sg(chan->device->dev, &s->sg_tx, 1, - DMA_TO_DEVICE); - if (!nent) { + s->tx_dma_addr = dma_map_single(chan->device->dev, + port->state->xmit.buf, + UART_XMIT_SIZE, + DMA_TO_DEVICE); + if (dma_mapping_error(chan->device->dev, s->tx_dma_addr)) { dev_warn(port->dev, "Failed mapping Tx DMA descriptor\n"); dma_release_channel(chan); s->chan_tx = NULL; } else { - dev_dbg(port->dev, "%s: mapped %d@%p to %pad\n", - __func__, - sg_dma_len(&s->sg_tx), port->state->xmit.buf, - &sg_dma_address(&s->sg_tx)); + dev_dbg(port->dev, "%s: mapped %lu@%p to %pad\n", + __func__, UART_XMIT_SIZE, + port->state->xmit.buf, &s->tx_dma_addr); } - s->sg_len_tx = nent; - INIT_WORK(&s->work_tx, work_fn_tx); } -- 2.34.1