On Wed, Apr 04, 2018 at 09:50:15AM +0200, Einar Vading wrote:
> When using RS485 in half duplex mode the RTS line is typically used to
> toggle receive/transmit on the transceiver IC. As some protocols (OSDP
> f.ex.) specify that the slave should respond within some short time period,
> it is important that the RTS line toggles the transceiver from transmit
> mode to receive mode within that time.
>
> This change puts a pm_qos requirement on CPU_DMA_LATENCY when in RS485 tx
> mode so that CPU wake times won't cause to long delays.
>
> Signed-off-by: Einar Vading <einarv@xxxxxxxx>
> ---
> drivers/tty/serial/imx.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 521500c..9051e07 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -39,6 +39,7 @@
> #include <linux/of_device.h>
> #include <linux/io.h>
> #include <linux/dma-mapping.h>
> +#include <linux/pm_qos.h>
>
> #include <asm/irq.h>
> #include <linux/platform_data/serial-imx.h>
> @@ -228,6 +229,7 @@ struct imx_port {
> unsigned int dma_tx_nents;
> unsigned int saved_reg[10];
> bool context_saved;
> + struct pm_qos_request pm_qos_req;
> };
>
> struct imx_port_ucrs {
> @@ -384,6 +386,7 @@ static void imx_stop_tx(struct uart_port *port)
> temp = readl(port->membase + UCR4);
> temp &= ~UCR4_TCEN;
> writel(temp, port->membase + UCR4);
> + pm_qos_update_request(&sport->pm_qos_req, PM_QOS_DEFAULT_VALUE);
> }
> }
>
> @@ -576,6 +579,7 @@ static void imx_start_tx(struct uart_port *port)
> unsigned long temp;
>
> if (port->rs485.flags & SER_RS485_ENABLED) {
> + pm_qos_update_request(&sport->pm_qos_req, 0);
> temp = readl(port->membase + UCR2);
> if (port->rs485.flags & SER_RS485_RTS_ON_SEND)
> imx_port_rts_active(sport, &temp);
> @@ -2216,6 +2220,9 @@ static int serial_imx_probe(struct platform_device *pdev)
> }
> }
>
> + pm_qos_add_request(&sport->pm_qos_req, PM_QOS_CPU_DMA_LATENCY,
> + PM_QOS_DEFAULT_VALUE);
> +
> imx_ports[sport->port.line] = sport;
>
> platform_set_drvdata(pdev, sport);
> @@ -2227,6 +2234,8 @@ static int serial_imx_remove(struct platform_device *pdev)
> {
> struct imx_port *sport = platform_get_drvdata(pdev);
>
> + pm_qos_remove_request(&sport->pm_qos_req);
> +
> return uart_remove_one_port(&imx_reg, &sport->port);
> }
This patch does not apply to my tree at all. Can you please rebase it
against the tty-testing branch of my tty.git tree and resend if it is
still needed?
thanks,
greg k-h
--
To unsubscribe from this list: send the line "unsubscribe linux-serial" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
