linux-kernel - Re: [PATCH V1] serial: imx: revert setup DCEDTE early and ensure DCD and RI irqs to be off

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Date:   Tue, 23 May 2017 16:37:15 +0200
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Steve Twiss <stwiss.opensource@...semi.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        LINUX-KERNEL <linux-kernel@...r.kernel.org>,
        LINUX-SERIAL <linux-serial@...r.kernel.org>,
        Lucas Stach <l.stach@...gutronix.de>,
        Support Opensource <Support.Opensource@...semi.com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>
Subject: Re: [PATCH V1] serial: imx: revert setup DCEDTE early and ensure DCD
 and RI irqs to be off

Hallo Steve,

On Tue, May 23, 2017 at 02:28:11PM +0000, Steve Twiss wrote:
> On 23 May 2017 15:10, Uwe Kleine-König wrote:
> > Subject: Re: [PATCH V1] serial: imx: revert setup DCEDTE early and ensure DCD and RI irqs to be off
> > On Tue, May 23, 2017 at 01:17:26PM +0100, Steve Twiss wrote:
> > >
> > > Revert the commit e61c38d85b7392e ("serial: imx: setup DCEDTE early and
> > > ensure DCD and RI irqs to be off")
> > >
> > > The patch submitted to setup DCEDTE early and ensure DCD and RI irqs to
> > > be off, causes a serial console display problem the i.MX6Q SABRESD board.
> > > The console becomes unreadable and unwritable.
> > >
> > > Tested-by: Steve Twiss <stwiss.opensource@...semi.com>
> > > Signed-off-by: Steve Twiss <stwiss.opensource@...semi.com>
> > 
> > You're not the first to report this issue but you still have the chance
> > to be the first to test a suggested patch for it.
> 
> I've just applied your patch against a clean linux-next/v4.12-rc2
> I added your patch ...
> 
> > 	http://marc.info/?l=linux-serial&m=149434029912947&w=2
> 
> (this one?)
> 
> diff --git a/gp_sparse/linux-next/v4.12-rc2/drivers/tty/serial/imx.c b/gp_sparse/linux-next/v4.12-rc2/drivers/tty/serial/imx.c
> index 33509b4..2182548 100644
> --- a/gp_sparse/linux-next/v4.12-rc2/drivers/tty/serial/imx.c
> +++ b/gp_sparse/linux-next/v4.12-rc2/drivers/tty/serial/imx.c
> @@ -2193,9 +2193,14 @@ static int serial_imx_probe(struct platform_device *pdev)
>                  */
>                 writel(IMX21_UCR3_RXDMUXSEL | UCR3_ADNIMP | UCR3_DSR,
>                        sport->port.membase + UCR3);
> -
>         } else {
> +               unsigned long ucr3 = UCR3_DSR;
> +
> +               if (!is_imx1_uart(sport))
> +                       ucr3 |= IMX21_UCR3_RXDMUXSEL | UCR3_ADNIMP;
> +
>                 writel(0, sport->port.membase + UFCR);
> +               writel(ucr3, sport->port.membase + UCR3);
>         }
>  
>         clk_disable_unprepare(sport->clk_ipg);
> 
Yeah, that's the patch I meant.

> I've added that to my working directory, but I am still seeing the corrupted
> console output on the i.MX6 Q (quad) board.

I don't have a failing board (I think). So here are a few questions
about yours:

 - how does the dts snippet for your failing device look like?
 - This is not the device the console runs on, right?
 - Can you initialize the device in the bootloader and check if it is
   working there?
 - Does it make a difference in Linux if the bootloader used the device
   before?
 - Can you dump the register space of the uart with v4.12-rc2 and
   v4.12-rc2 + revert of e61c38d85b7392e?

Best regards
Uwe

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