From a3015affdf76ef279fbbb3710a220bab7e9ea04b Mon Sep 17 00:00:00 2001 From: Nandor Han Date: Wed, 28 Jun 2017 12:15:14 +0200 Subject: [PATCH] serial: imx-serial - move DMA buffer configuration to DT The size of the DMA buffer can affect the delta time between data being produced and data being consumed. Basically the DMA system will move data to tty buffer when a) DMA buffer is full b) serial line is idle. The situation is visible when producer generates data continuously and there is no possibility for idle line. At this point the DMA buffer is directly affecting the delta time. The patch will add the possibility to configure the DMA buffers in DT, which case by case can be configured separately for every driver instance. The DT configuration is optional and in case missing the driver will use the 4096 buffer with 4 periods (as before), therefore no clients are impacted by this change. Signed-off-by: Nandor Han Signed-off-by: Romain Perier Signed-off-by: Greg Kroah-Hartman --- .../devicetree/bindings/serial/fsl-imx-uart.txt | 2 ++ drivers/tty/serial/imx.c | 25 +++++++++++++++------- 2 files changed, 19 insertions(+), 8 deletions(-) diff --git a/Documentation/devicetree/bindings/serial/fsl-imx-uart.txt b/Documentation/devicetree/bindings/serial/fsl-imx-uart.txt index 574c3a2c77d5..e6b572409cf5 100644 --- a/Documentation/devicetree/bindings/serial/fsl-imx-uart.txt +++ b/Documentation/devicetree/bindings/serial/fsl-imx-uart.txt @@ -9,6 +9,7 @@ Optional properties: - fsl,irda-mode : Indicate the uart supports irda mode - fsl,dte-mode : Indicate the uart works in DTE mode. The uart works in DCE mode by default. +- fsl,dma-size : Indicate the size of the DMA buffer and its periods Please check Documentation/devicetree/bindings/serial/serial.txt for the complete list of generic properties. @@ -28,4 +29,5 @@ uart1: serial@73fbc000 { interrupts = <31>; uart-has-rtscts; fsl,dte-mode; + fsl,dma-size = <1024 4>; }; diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index e33da75ceac5..9e3162bf3bd1 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -186,6 +186,11 @@ #define UART_NR 8 +/* RX DMA buffer periods */ +#define RX_DMA_PERIODS 4 +#define RX_BUF_SIZE (PAGE_SIZE) + + /* i.MX21 type uart runs on all i.mx except i.MX1 and i.MX6q */ enum imx_uart_type { IMX1_UART, @@ -221,6 +226,7 @@ struct imx_port { struct dma_chan *dma_chan_rx, *dma_chan_tx; struct scatterlist rx_sgl, tx_sgl[2]; void *rx_buf; + unsigned int rx_buf_size; struct circ_buf rx_ring; unsigned int rx_periods; dma_cookie_t rx_cookie; @@ -961,8 +967,6 @@ static void imx_timeout(unsigned long data) } } -#define RX_BUF_SIZE (PAGE_SIZE) - /* * There are two kinds of RX DMA interrupts(such as in the MX6Q): * [1] the RX DMA buffer is full. @@ -1045,9 +1049,6 @@ static void dma_rx_callback(void *data) } } -/* RX DMA buffer periods */ -#define RX_DMA_PERIODS 4 - static int start_rx_dma(struct imx_port *sport) { struct scatterlist *sgl = &sport->rx_sgl; @@ -1058,9 +1059,8 @@ static int start_rx_dma(struct imx_port *sport) sport->rx_ring.head = 0; sport->rx_ring.tail = 0; - sport->rx_periods = RX_DMA_PERIODS; - sg_init_one(sgl, sport->rx_buf, RX_BUF_SIZE); + sg_init_one(sgl, sport->rx_buf, sport->rx_buf_size); ret = dma_map_sg(dev, sgl, 1, DMA_FROM_DEVICE); if (ret == 0) { dev_err(dev, "DMA mapping error for RX.\n"); @@ -1171,7 +1171,7 @@ static int imx_uart_dma_init(struct imx_port *sport) goto err; } - sport->rx_buf = kzalloc(PAGE_SIZE, GFP_KERNEL); + sport->rx_buf = kzalloc(sport->rx_buf_size, GFP_KERNEL); if (!sport->rx_buf) { ret = -ENOMEM; goto err; @@ -2036,6 +2036,7 @@ static int serial_imx_probe_dt(struct imx_port *sport, { struct device_node *np = pdev->dev.of_node; int ret; + u32 dma_buf_size[2]; sport->devdata = of_device_get_match_data(&pdev->dev); if (!sport->devdata) @@ -2059,6 +2060,14 @@ static int serial_imx_probe_dt(struct imx_port *sport, if (of_get_property(np, "rts-gpios", NULL)) sport->have_rtsgpio = 1; + if (!of_property_read_u32_array(np, "fsl,dma-size", dma_buf_size, 2)) { + sport->rx_buf_size = dma_buf_size[0] * dma_buf_size[1]; + sport->rx_periods = dma_buf_size[1]; + } else { + sport->rx_buf_size = RX_BUF_SIZE; + sport->rx_periods = RX_DMA_PERIODS; + } + return 0; } #else -- 2.11.0