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Date:   Thu, 1 Sep 2022 21:35:23 +0200
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Subject: Re: [PATCH v2 00/41] drm: Analog TV Improvements
To:     Maxime Ripard <maxime@cerno.tech>,
        Maxime Ripard <mripard@kernel.org>,
        Ben Skeggs <bskeggs@redhat.com>,
        David Airlie <airlied@linux.ie>, Chen-Yu Tsai <wens@csie.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Lyude Paul <lyude@redhat.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Samuel Holland <samuel@sholland.org>,
        Karol Herbst <kherbst@redhat.com>,
        Emma Anholt <emma@anholt.net>, Daniel Vetter <daniel@ffwll.ch>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Dom Cobley <dom@raspberrypi.com>
Cc:     Hans de Goede <hdegoede@redhat.com>,
        linux-arm-kernel@lists.infradead.org,
        Phil Elwell <phil@raspberrypi.com>,
        intel-gfx@lists.freedesktop.org,
        Dave Stevenson <dave.stevenson@raspberrypi.com>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        nouveau@lists.freedesktop.org, linux-sunxi@lists.linux.dev,
        Mateusz Kwiatkowski <kfyatek+publicgit@gmail.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        =?UTF-8?Q?Noralf_Tr=c3=b8nnes?= <noralf@tronnes.org>
References: <20220728-rpi-analog-tv-properties-v2-0-459522d653a7@cerno.tech>
From:   =?UTF-8?Q?Noralf_Tr=c3=b8nnes?= <noralf@tronnes.org>
In-Reply-To: <20220728-rpi-analog-tv-properties-v2-0-459522d653a7@cerno.tech>
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Den 29.08.2022 15.11, skrev Maxime Ripard:
> Hi,
> 
> 
> 
> Here's a series aiming at improving the command line named modes support,
> 
> and more importantly how we deal with all the analog TV variants.
> 
> 
> 
> The named modes support were initially introduced to allow to specify the
> 
> analog TV mode to be used.
> 
> 
> 
> However, this was causing multiple issues:
> 
> 
> 
>   * The mode name parsed on the command line was passed directly to the
> 
>     driver, which had to figure out which mode it was suppose to match;
> 
> 
> 
>   * Figuring that out wasn't really easy, since the video= argument or what
> 
>     the userspace might not even have a name in the first place, but
> 
>     instead could have passed a mode with the same timings;
> 
> 
> 
>   * The fallback to matching on the timings was mostly working as long as
> 
>     we were supporting one 525 lines (most likely NSTC) and one 625 lines
> 
>     (PAL), but couldn't differentiate between two modes with the same
> 
>     timings (NTSC vs PAL-M vs NSTC-J for example);
> 
> 
> 
>   * There was also some overlap with the tv mode property registered by
> 
>     drm_mode_create_tv_properties(), but named modes weren't interacting
> 
>     with that property at all.
> 
> 
> 
>   * Even though that property was generic, its possible values were
> 
>     specific to each drivers, which made some generic support difficult.
> 
> 
> 
> Thus, I chose to tackle in multiple steps:
> 
> 
> 
>   * A new TV norm property was introduced, with generic values, each driver
> 
>     reporting through a bitmask what standard it supports to the userspace;
> 
> 
> 
>   * This option was added to the command line parsing code to be able to
> 
>     specify it on the kernel command line, and new atomic_check and reset
> 
>     helpers were created to integrate properly into atomic KMS;
> 
> 
> 
>   * The named mode parsing code is now creating a proper display mode for
> 
>     the given named mode, and the TV standard will thus be part of the
> 
>     connector state;
> 
> 
> 
>   * Two drivers were converted and tested for now (vc4 and sun4i), with
> 
>     some backward compatibility code to translate the old TV mode to the
> 
>     new TV mode;
> 
> 
> 
> Unit tests were created along the way.
> 
> 
> 
> One can switch from NTSC to PAL now using (on vc4)
> 
> 
> 
> modetest -M vc4  -s 53:720x480i -w 53:'tv norm':0
> 
> 
> 
> modetest -M vc4 -s 53:720x480i -w 53:'tv norm':4
> 

The property name has changed, this gives me PAL:

$ modetest -M vc4 -s 45:720x576i -w 45:'TV mode':4


I have finally found a workaround for my kernel hangs.

Dom had a look at my kernel and found that the VideoCore was fine, and
he said this:

> That suggests cause of lockup was on arm side rather than VC side.
>
> But it's hard to diagnose further. Once you've had a peripheral not
> respond, the AXI bus locks up and no further operations are possible.
> Usual causes of this are required clocks being stopped or domains
> disabled and then trying to access the hardware.
>

So when I got this on my 64-bit build:

[  166.702171] SError Interrupt on CPU1, code 0x00000000bf000002 -- SError
[  166.702187] CPU: 1 PID: 8 Comm: kworker/u8:0 Tainted: G        W
    5.19.0-rc6-00096-gba7973977976-dirty #1
[  166.702200] Hardware name: Raspberry Pi 4 Model B Rev 1.1 (DT)
[  166.702206] Workqueue: events_freezable_power_ thermal_zone_device_check
[  166.702231] pstate: 200000c5 (nzCv daIF -PAN -UAO -TCO -DIT -SSBS
BTYPE=--)
[  166.702242] pc : regmap_mmio_read32le+0x10/0x28
[  166.702261] lr : regmap_mmio_read+0x44/0x70
...
[  166.702606]  bcm2711_get_temp+0x58/0xb0 [bcm2711_thermal]

I wondered if that reg read was stalled due to a clock being stopped.

Lo and behold, disabling runtime pm and keeping the vec clock running
all the time fixed it[1].

I don't know what the problem is, but at least I can now test this patchset.

[1] https://gist.github.com/notro/23b984e7fa05cfbda2db50a421cac065

Noralf.