linux-kernel - Re: [PATCH v1 05/35] drm/connector: Add TV standard property

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Date:   Thu, 18 Aug 2022 17:01:38 +0200
From:   Noralf Trønnes <noralf@...nnes.org>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Jernej Skrabec <jernej.skrabec@...il.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Jerome Brunet <jbrunet@...libre.com>,
        Samuel Holland <samuel@...lland.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Daniel Vetter <daniel@...ll.ch>, Emma Anholt <emma@...olt.net>,
        David Airlie <airlied@...ux.ie>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Kevin Hilman <khilman@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Phil Elwell <phil@...pberrypi.com>,
        Mateusz Kwiatkowski <kfyatek+publicgit@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        linux-amlogic@...ts.infradead.org, dri-devel@...ts.freedesktop.org,
        Dom Cobley <dom@...pberrypi.com>
Subject: Re: [PATCH v1 05/35] drm/connector: Add TV standard property



Den 18.08.2022 01.23, skrev Noralf Trønnes:
> 
> 
> Den 17.08.2022 15.11, skrev Noralf Trønnes:
>>
>>
>> Den 17.08.2022 13.46, skrev Maxime Ripard:
>>> On Tue, Aug 16, 2022 at 09:35:24PM +0200, Noralf Trønnes wrote:
>>>> Den 16.08.2022 11.49, skrev Maxime Ripard:
>>>>> On Tue, Aug 16, 2022 at 11:42:20AM +0200, Noralf Trønnes wrote:
>>>>>> Den 16.08.2022 10.26, skrev Maxime Ripard:
>>>>>>> Hi,
>>>>>>>
>>>>>>> On Mon, Aug 08, 2022 at 02:44:56PM +0200, Noralf Trønnes wrote:
>>>>>>>> Den 29.07.2022 18.34, skrev Maxime Ripard:
>>>>>>>>> The TV mode property has been around for a while now to select and get the
>>>>>>>>> current TV mode output on an analog TV connector.
>>>>>>>>>
>>>>>>>>> Despite that property name being generic, its content isn't and has been
>>>>>>>>> driver-specific which makes it hard to build any generic behaviour on top
>>>>>>>>> of it, both in kernel and user-space.
>>>>>>>>>
>>>>>>>>> Let's create a new bitmask tv norm property, that can contain any of the
>>>>>>>>> analog TV standards currently supported by kernel drivers. Each driver can
>>>>>>>>> then pass in a bitmask of the modes it supports.
>>>>>>>>>
>>>>>>>>> We'll then be able to phase out the older tv mode property.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Maxime Ripard <maxime@...no.tech>
>>>>>>>>>
> 
>>>> How do you test the property? I've used modetest but I can only change
>>>> to a tv.mode that matches the current display mode. I can't switch from
>>>> ntsc to pal for instance.
>>>
>>> Yep, if you want to change from PAL to NTSC, it will require a new mode.
>>>
>>
>> So userspace has to check tv.mode first and then create a display mode
>> the driver will accept if switching to a different display mode is
>> necessary? In other words, userspace can't discover from the kernel
>> which display modes a certain tv.mode/norm provides before it is
>> selected? If so, maybe libdrm should have some function(s) to deal with
>> switching between modes that require a different display mode since
>> knowledge about which display modes a tv.mode supports is needed before
>> hand.
>>
> 
> I haven't used vc4 on Pi4 in mainline before and have finally gotten it
> to work.
> 
> I see that the connector reports 2 modes that together fit all tv.norms
> so userspace doesn't have to contruct a display mode, but it does need
> to know which display mode belongs to a certain tv.norm.
> 
> When I try to use modetest I'm unable to set a mode:
> 
> pi@...t:~ $ modetest -M vc4 -s 45:720x480i
> setting mode 720x480i-29.97Hz on connectors 45, crtc 68
> failed to set mode: Function not implemented
> 
> The errno is misleading, modetest does a drmModeDirtyFB before checking
> the error returned by drmModeSetCrtc.
> 
> Setting the property succeeds, but the modeset still fails:
> 
> pi@...t:~ $ modetest -M vc4 -s 45:720x480i -w 45:"tv norm":2
> setting mode 720x480i-29.97Hz on connectors 45, crtc 68
> failed to set mode: Function not implemented
> 
> pi@...t:~ $ modetest -M vc4 -c
>         37 tv norm:
>                 flags: bitmask
>                 values: NTSC-443=0x1 NTSC-J=0x2 NTSC-M=0x4 PAL-B=0x10
> PAL-M=0x200 PAL-N=0x400 SECAM-B=0x2000
>                 value: 2
> 
> Here's the log, can you see if there's anything obvious in there:
> https://gist.github.com/notro/a079498bf6b64327105752b2bafa8858
> 

I'm one step closer as I now have fbcon working, I had forgotten to add
enable_tvout=1 and I had disable_fw_kms_setup=1 which disables the
video= mode on the kernel commandline.

modetest still fails though, after alot of printk sprinkling, I've
tracked it down to the drm_mode_equal test in
drm_atomic_helper_connector_tv_check(). The aspect ratios differ:

[   61.336295] drm_atomic_helper_connector_tv_check:
mode->picture_aspect_ratio=1
[   61.336301] drm_atomic_helper_connector_tv_check:
&crtc_state->mode->picture_aspect_ratio=0

Noralf.