[v1,2/2] tty: serial: tegra: Optimize DMA buffer synchronization

Message ID 20200112180919.5194-3-digetx@gmail.com
State New
Headers show
Series
  • NVIDIA Tegra serial driver improvements
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Commit Message

Dmitry Osipenko Jan. 12, 2020, 6:09 p.m.
Synchronize only the dirty part of DMA buffer in order to avoid
unnecessary overhead of syncing of the clean part, which is the case
of every serial DMA transfer in practice.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/tty/serial/serial-tegra.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

Patch

diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
index 3b495e7c9534..33034b852a51 100644
--- a/drivers/tty/serial/serial-tegra.c
+++ b/drivers/tty/serial/serial-tegra.c
@@ -534,11 +534,12 @@  static int tegra_uart_start_tx_dma(struct tegra_uart_port *tup,
 	struct circ_buf *xmit = &tup->uport.state->xmit;
 	dma_addr_t tx_phys_addr;
 
-	dma_sync_single_for_device(tup->uport.dev, tup->tx_dma_buf_phys,
-				UART_XMIT_SIZE, DMA_TO_DEVICE);
-
 	tup->tx_bytes = count & ~(0xF);
 	tx_phys_addr = tup->tx_dma_buf_phys + xmit->tail;
+
+	dma_sync_single_for_device(tup->uport.dev, tx_phys_addr,
+				   tup->tx_bytes, DMA_TO_DEVICE);
+
 	tup->tx_dma_desc = dmaengine_prep_slave_single(tup->tx_dma_chan,
 				tx_phys_addr, tup->tx_bytes, DMA_MEM_TO_DEV,
 				DMA_PREP_INTERRUPT);
@@ -680,7 +681,7 @@  static void tegra_uart_copy_rx_to_tty(struct tegra_uart_port *tup,
 		return;
 
 	dma_sync_single_for_cpu(tup->uport.dev, tup->rx_dma_buf_phys,
-				TEGRA_UART_RX_DMA_BUFFER_SIZE, DMA_FROM_DEVICE);
+				count, DMA_FROM_DEVICE);
 	copied = tty_insert_flip_string(tty,
 			((unsigned char *)(tup->rx_dma_buf_virt)), count);
 	if (copied != count) {
@@ -688,7 +689,7 @@  static void tegra_uart_copy_rx_to_tty(struct tegra_uart_port *tup,
 		dev_err(tup->uport.dev, "RxData copy to tty layer failed\n");
 	}
 	dma_sync_single_for_device(tup->uport.dev, tup->rx_dma_buf_phys,
-				TEGRA_UART_RX_DMA_BUFFER_SIZE, DMA_TO_DEVICE);
+				   count, DMA_TO_DEVICE);
 }
 
 static void tegra_uart_rx_buffer_push(struct tegra_uart_port *tup,
@@ -788,8 +789,6 @@  static int tegra_uart_start_rx_dma(struct tegra_uart_port *tup)
 	tup->rx_dma_active = true;
 	tup->rx_dma_desc->callback = tegra_uart_rx_dma_complete;
 	tup->rx_dma_desc->callback_param = tup;
-	dma_sync_single_for_device(tup->uport.dev, tup->rx_dma_buf_phys,
-				count, DMA_TO_DEVICE);
 	tup->rx_bytes_requested = count;
 	tup->rx_cookie = dmaengine_submit(tup->rx_dma_desc);
 	dma_async_issue_pending(tup->rx_dma_chan);
@@ -1154,6 +1153,9 @@  static int tegra_uart_dma_channel_allocate(struct tegra_uart_port *tup,
 			dma_release_channel(dma_chan);
 			return -ENOMEM;
 		}
+		dma_sync_single_for_device(tup->uport.dev, dma_phys,
+					   TEGRA_UART_RX_DMA_BUFFER_SIZE,
+					   DMA_TO_DEVICE);
 		dma_sconfig.src_addr = tup->uport.mapbase;
 		dma_sconfig.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
 		dma_sconfig.src_maxburst = tup->cdata->max_dma_burst_bytes;