[PATCH v3 1/6] serial: imx: remove CTSC and CTS handling from imx_disable_dma
u.kleine-koenig at pengutronix.de
Thu Sep 21 11:20:17 PDT 2017
On Thu, Sep 21, 2017 at 05:18:12PM +0100, Martyn Welch wrote:
> From: Nandor Han <nandor.han at 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
> This configuration of the CTSC and CTS bits are therefore not needed.
> Signed-off-by: Nandor Han <nandor.han at ge.com>
> Signed-off-by: Romain Perier <romain.perier at collabora.com>
> Signed-off-by: Martyn Welch <martyn.welch at 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.
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
More information about the linux-arm-kernel