lkml.org 
[lkml]   [2017]   [Sep]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 1/6] serial: imx: remove CTSC and CTS handling from imx_disable_dma
On Thu, Sep 21, 2017 at 05:18:12PM +0100, Martyn Welch wrote:
> From: Nandor Han <nandor.han@ge.com>
>
> The CTSC and CTS bits affect operation of the CTS/RTS hardware flow
> control signal (depending on whether the device is in DCE or DTE mode) and
> are not related to DMA. When in RS-232 mode, the driver is using the
> automatic CTSC control based on a rxFIFO fill level unless the state of
> the CTS signal is explictly set via an ioctl call.
>
> Previous improvements to the imx serial driver have resulted on
> imx_disable_dma() only being called on shutdown, by which point the
> serial core has already correctly deasserted CTS.
>
> Testing shows that without this handling in imx_disable_dma() the CTS
> signal state is set correctly when the device is open and TIOCM_RTS is
> set/cleared via the TIOCMGET ioctl. The CTS signal is also correctly
> deasserted when the device file is closed.

With that block kept CTS set once more to inactive. So the block doesn't
hurt and is "only" superflous, right?

> When in RS-485 mode, the driver uses the CTS signal very differently and
> appears to control it via calls to imx_port_rts_active() and
> imx_port_rts_inactive().
>
> This configuration of the CTSC and CTS bits are therefore not needed.
>
> Signed-off-by: Nandor Han <nandor.han@ge.com>
> Signed-off-by: Romain Perier <romain.perier@collabora.com>
> Signed-off-by: Martyn Welch <martyn.welch@collabora.co.uk>
> ---
> drivers/tty/serial/imx.c | 5 -----
> 1 file changed, 5 deletions(-)
>
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index fe368a4..d90dae3 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -1225,11 +1225,6 @@ static void imx_disable_dma(struct imx_port *sport)
> temp &= ~(UCR1_RDMAEN | UCR1_TDMAEN | UCR1_ATDMAEN);
> writel(temp, sport->port.membase + UCR1);
>
> - /* clear UCR2 */
> - temp = readl(sport->port.membase + UCR2);
> - temp &= ~(UCR2_CTSC | UCR2_CTS | UCR2_ATEN);
> - writel(temp, sport->port.membase + UCR2);

The commit log doesn't mention ATEN, I guess that one just doesn't
matter any more at this stage? Would be nice to point out though.

Best regards
Uwe

--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |

\
 
 \ /
  Last update: 2017-09-21 20:21    [W:0.063 / U:8.732 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site