linux-kernel - Re: [PATCH v3 032/105] drm/vc4: crtc: Enable and disable the PV in atomic

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Date:   Wed, 3 Jun 2020 17:26:53 +0200
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Eric Anholt <eric@...olt.net>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        LKML <linux-kernel@...r.kernel.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        bcm-kernel-feedback-list@...adcom.com,
        Phil Elwell <phil@...pberrypi.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 032/105] drm/vc4: crtc: Enable and disable the PV in
 atomic_enable / disable

Hi Maxime,

Am 03.06.20 um 15:14 schrieb Maxime Ripard:
> Hi Stefan,
>
> On Tue, Jun 02, 2020 at 10:03:13PM +0200, Stefan Wahren wrote:
>> Am 02.06.20 um 21:31 schrieb Eric Anholt:
>>> On Tue, Jun 2, 2020 at 8:02 AM Dave Stevenson
>>> <dave.stevenson@...pberrypi.com> wrote:
>>>> Hi Maxime and Eric
>>>>
>>>> On Tue, 2 Jun 2020 at 15:12, Maxime Ripard <maxime@...no.tech> wrote:
>>>>> Hi Eric
>>>>>
>>>>> On Wed, May 27, 2020 at 09:54:44AM -0700, Eric Anholt wrote:
>>>>>> On Wed, May 27, 2020 at 8:50 AM Maxime Ripard <maxime@...no.tech> wrote:
>>>>>>> The VIDEN bit in the pixelvalve currently being used to enable or disable
>>>>>>> the pixelvalve seems to not be enough in some situations, which whill end
>>>>>>> up with the pixelvalve stalling.
>>>>>>>
>>>>>>> In such a case, even re-enabling VIDEN doesn't bring it back and we need to
>>>>>>> clear the FIFO. This can only be done if the pixelvalve is disabled though.
>>>>>>>
>>>>>>> In order to overcome this, we can configure the pixelvalve during
>>>>>>> mode_set_no_fb, but only enable it in atomic_enable and flush the FIFO
>>>>>>> there, and in atomic_disable disable the pixelvalve again.
>>>>>> What displays has this been tested with?  Getting this sequencing
>>>>>> right is so painful, and things like DSI are tricky to get to light
>>>>>> up.
>>>>> That FIFO is between the HVS and the HDMI PVs, so this was obviously
>>>>> tested against that. Dave also tested the DSI output IIRC, so we should
>>>>> be covered here.
>>>> DSI wasn't working on the first patch set that Maxime sent - I haven't
>>>> tested this one as yet but will do so.
>>>> DPI was working early on to both an Adafruit 800x480 DPI panel, and
>>>> via a VGA666 as VGA.
>>>> HDMI is obviously working.
>>>> VEC is being ignored now. The clock structure is more restricted than
>>>> earlier chips, so to get the required clocks for the VEC without using
>>>> fractional divides it compromises the clock that other parts of the
>>>> system can run at (IIRC including the ARM). That's why the VEC has to
>>>> be explicitly enabled for the firmware to enable it as the only
>>>> output. It's annoying, but that's just a restriction of the chip.
>>> I'm more concerned with "make sure we don't regress pre-pi4 with this
>>> series" than "pi4 displays all work from the beginning"
>> unfortuntely i can confirm this. With this patch series (using Maxime's
>> git repo with multi_v7_defconfig) my Raspberry Pi 3 B hangs up while
>> starting X (screen stays black, heartbeat stops, no more output at the
>> debug UART). AFAIR v2 didn't had this issue.
> Did it happen with a DSI display or something else?
with my HDMI display (HP ZR2440w). At first everything looks good
(Raspbian splash screen is displayed), but before the real workspace is
displayed this issue happens.
> I've been trying to setup the DSI display on an RPi3 today, but noticed
> that it looks like there's a regression in next that prevents the HDMI
> driver to load entirely (without my patches).

I took your rpi4-kms branch and switched before your series and
everything works fine. I will try to bisect the offending commit.

Stefan

>
> Maxime