linux-kernel - Re: [PATCH] drm/sun4i: fix HSYNC and VSYNC polarity

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Message-ID: <CANwerB2GGLT6fOZk7Q8RXhmiEb7KYnQrx-Rj5AgGn-YPCiMH4g@mail.gmail.com>
Date:   Thu, 13 Dec 2018 13:55:14 +1100
From:   Jonathan Liu <net147@...il.com>
To:     Giulio Benetti <giulio.benetti@...ronovasrl.com>
Cc:     Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Chen-Yu Tsai <wens@...e.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/sun4i: fix HSYNC and VSYNC polarity

Hi Giulio,

On Wed, 12 Dec 2018 at 04:39, Giulio Benetti
<giulio.benetti@...ronovasrl.com> wrote:
>
> Forgot to ask you,
>
> Il 11/12/2018 18:20, Giulio Benetti ha scritto:
> > Hi Jonathan,
> >
> > Il 11/12/2018 11:49, Jonathan Liu ha scritto:
> >> Hi Giulio,
> >>
> >> On Thu, 6 Dec 2018 at 22:00, Giulio Benetti
> >> <giulio.benetti@...ronovasrl.com> wrote:
> >>>
> >>> Hi Jonathan,
> >>>
> >>> Il 06/12/2018 08:29, Jonathan Liu ha scritto:
> >>>> Hi Giulio,
> >>>>
> >>>> On Thu, 15 Feb 2018 at 17:54, Giulio Benetti
> >>>> <giulio.benetti@...ronovasrl.com> wrote:
> >>>>>
> >>>>> Differently from other Lcd signals, HSYNC and VSYNC signals
> >>>>> result inverted if their bits are cleared to 0.
> >>>>>
> >>>>> Invert their settings of IO_POL register.
> >>>>>
> >>>>> Signed-off-by: Giulio Benetti <giulio.benetti@...ronovasrl.com>
> >>>>> ---
> >>>>>    drivers/gpu/drm/sun4i/sun4i_tcon.c | 4 ++--
> >>>>>    1 file changed, 2 insertions(+), 2 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> >>>>> b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> >>>>> index 3c15cf2..aaf911a 100644
> >>>>> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> >>>>> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> >>>>> @@ -389,10 +389,10 @@ static void sun4i_tcon0_mode_set_rgb(struct
> >>>>> sun4i_tcon *tcon,
> >>>>>                        SUN4I_TCON0_BASIC3_H_SYNC(hsync));
> >>>>>
> >>>>>           /* Setup the polarity of the various signals */
> >>>>> -       if (!(mode->flags & DRM_MODE_FLAG_PHSYNC))
> >>>>> +       if (mode->flags & DRM_MODE_FLAG_PHSYNC)
> >>>>>                   val |= SUN4I_TCON0_IO_POL_HSYNC_POSITIVE;
> >>>>>
> >>>>> -       if (!(mode->flags & DRM_MODE_FLAG_PVSYNC))
> >>>>> +       if (mode->flags & DRM_MODE_FLAG_PVSYNC)
> >>>>>                   val |= SUN4I_TCON0_IO_POL_VSYNC_POSITIVE;
> >>>>>
> >>>>>           regmap_update_bits(tcon->regs, SUN4I_TCON0_IO_POL_REG,
> >>>>
> >>>> I am running Linux 4.19.6 and noticed with Olimex LCD-OLinuXino-7TS 7"
> >>>> LCD touchscreen (Innolux AT070TN92) connected to Olimex
> >>>> A20-OLinuXino-MICRO that the image does not display correctly after
> >>>> this change.
> >>>> The image is shifted to the right.
> >>>>
> >>>> Reverting the change results in the image being displayed correctly on
> >>>> the screen.
> >>>>
> >>>> I have in the device tree a "panel" node with compatible =
> >>>> "innolux,at070tn92" which uses the timings in
> >>>> drivers/gpu/drm/panel/panel-simple.c.
> >>>>
> >>>> Any ideas?
> >>
> >>>
> >>> Checking Display Datasheet:
> >>> https://www.olimex.com/Products/Retired/A13-LCD7-TS/resources/S700-AT070TN92.pdf
> >>>
> >>>
> >>> Page 13 section 3.3.2 you can see it needs active low VS and HS.
> >>>
> >>> You can refer to this Thread and check scope captures about VS and HS
> >>> versus TCON0_IOPOL register:
> >>> https://lists.freedesktop.org/archives/dri-devel/2018-January/163874.html
> >>>
> >>>
> >>> There should be something that wrongly sets one of these or both:
> >>> mode->flags |= DRM_MODE_FLAG_PHSYNC;
> >>> and/or
> >>> mode->flags |= DRM_MODE_FLAG_PVSYNC;
> >>>
> >>> Checked in panel-simple.c but it's not there.
> >>
> >> flags is 0 because it is not assigned in the struct definition for the
> >> panel.
> >
> > I don't think it is 0, because otherwise IO_POL_REG wouldn't be set to
> > 0x03000000 but to 0.
> > What is checked is exactly mode->flags, so the problem seems to be
> > upstream.
> >
> > This is my doubt, it seems mode->flags is not initialized or overriden
> > at a certain point, this is why I want to debug it with Jtag tomorrow.
> >
> >> Before this change, TCON0_IO_POL_REG would be 0x03000000 (both bits
> >> set to 1) and image displays correctly > After this change,
> >> TCON0_IO_POL_REG is 0x00000000 (both bits set to 0)
> >> and image doesn't display correctly.
> >>
> >> Checked using "devmem2 0x01c0c088" on A20-OLinuXino-MICRO Rev J.
> >
> > 0x03000000 as I've triple checked with scope means Positive H/Vsync,
> > and 0x00000000 Negative H/VSync.
> >
> > Please check on the Thread I've pointed you above where there are all
> > the links to the scope captures.
> >
> > Are you completely sure you're using the correct panel?
> > This is because if with 0x03000000 it works correctly, it means that
> > you're using Positive VS and HS but on datasheet on Figure 3.2 it shows
> > that they must be negative.
> >
> > Do you have any chance to measure those signals with a scope?
> >
> > Tomorrow, while debugging, I'll re-check H/Vsync signals again.
> >
> > Kind regards

>
> Can you precisely point me the sources of:
> - u-boot
> - kernel
> - dts
>
> you're using?
>
> Thanks

U-Boot - git tag v2017.03
Linux - git tag v4.19.6
DTS - see device tree changes in
https://github.com/net147/linux/tree/sun7i-drm-wip but change the
compatible to "innolux,at070tn92"

Thanks.

Regards,
Jonathan