linux-kernel - Re: [PATCH] drm/meson: Fix atomic mode switching regression

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Message-ID: <a3d36c98-9d90-ff63-7ca8-77aff89f7f1a@baylibre.com>
Date:   Mon, 14 Jan 2019 16:25:58 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     daniel@...ll.ch, linux-amlogic@...ts.infradead.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/meson: Fix atomic mode switching regression

Hi Martin,

On 09/01/2019 23:18, Martin Blumenstingl wrote:
> Hi Neil,
> 
> On Wed, Jan 9, 2019 at 2:36 PM Neil Armstrong <narmstrong@...libre.com> wrote:
>>
>> Since commit 2bcd3ecab773 when switching mode from X11 (ubuntu mate for
>> example) the display gets blurry, looking like an invalid framebuffer width.
>>
>> This commit fixed atomic crtc modesetting but didn't update the display
>> parameters when changing mode, but only when starting a mode setting after
>> a crtc disable.
>>
>> This commit setups the crctc parameter in _begin() and _enable() to
>> take in account the current ctrc parameters.
>>
>> Reported-by: Tony McKahan <tonymckahan@...il.com>
>> Fixes: 2bcd3ecab773 ("drm/meson: Fixes for drm_crtc_vblank_on/off support")
>> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
>> ---
>>  drivers/gpu/drm/meson/meson_crtc.c | 16 +++++++++++++---
>>  1 file changed, 13 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/meson/meson_crtc.c b/drivers/gpu/drm/meson/meson_crtc.c
>> index 75d97f1b2e8f..5bb432021caf 100644
>> --- a/drivers/gpu/drm/meson/meson_crtc.c
>> +++ b/drivers/gpu/drm/meson/meson_crtc.c
>> @@ -82,14 +82,12 @@ static const struct drm_crtc_funcs meson_crtc_funcs = {
>>
>>  };
>>
>> -static void meson_crtc_enable(struct drm_crtc *crtc)
>> +static void meson_crtc_setup(struct drm_crtc *crtc)
>>  {
>>         struct meson_crtc *meson_crtc = to_meson_crtc(crtc);
>>         struct drm_crtc_state *crtc_state = crtc->state;
>>         struct meson_drm *priv = meson_crtc->priv;
>>
>> -       DRM_DEBUG_DRIVER("\n");
>> -
>>         if (!crtc_state) {
>>                 DRM_ERROR("Invalid crtc_state\n");
>>                 return;
>> @@ -98,6 +96,16 @@ static void meson_crtc_enable(struct drm_crtc *crtc)
>>         /* Enable VPP Postblend */
> nit-pick: this "enable" comment is now in meson_crtc_setup().
> I would drop it because my interpretation of the following lines is
> now "setting VPP_POSTBLEND_H_SIZE enables the VPP postblend"
> 
>>         writel(crtc_state->mode.hdisplay,
>>                priv->io_base + _REG(VPP_POSTBLEND_H_SIZE));
>> +}
>> +
>> +static void meson_crtc_enable(struct drm_crtc *crtc)
>> +{
>> +       struct meson_crtc *meson_crtc = to_meson_crtc(crtc);
>> +       struct meson_drm *priv = meson_crtc->priv;
>> +
>> +       DRM_DEBUG_DRIVER("\n");
>> +
>> +       meson_crtc_setup(crtc);
>>
>>         /* VD1 Preblend vertical start/end */
>>         writel(FIELD_PREP(GENMASK(11, 0), 2303),
>> @@ -121,6 +129,8 @@ static void meson_crtc_atomic_enable(struct drm_crtc *crtc,
>>
>>         if (!meson_crtc->enabled)
>>                 meson_crtc_enable(crtc);
>> +       else
>> +               meson_crtc_setup(crtc);
> it's probably only personal preference, but have you thought about
> re-ordering this:
>   meson_crtc_setup(crtc);
> 
>   if (!meson_crtc->enabled)
>     meson_crtc_enable(crtc);
> 
> with that you could get rid of the meson_crtc_setup() call in
> meson_crtc_enable(), leaving only one code-path (instead of two) which
> calls meson_crtc_setup()

All of this is wrong, I only needed to use `atomic_commit_tail = drm_atomic_helper_commit_tail_rpm`
in meson_drv for the fbdev.

This fix is wrong, pushing a right one.

Neil

> 
> 
> Regards
> Martin
>