linux-kernel - Re: [PATCH v2 00/41] drm: Analog TV Improvements

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Date:   Mon, 5 Sep 2022 17:17:18 +0200
From:   Noralf Trønnes <noralf@...nnes.org>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Ben Skeggs <bskeggs@...hat.com>, David Airlie <airlied@...ux.ie>,
        Chen-Yu Tsai <wens@...e.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Lyude Paul <lyude@...hat.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>,
        Karol Herbst <kherbst@...hat.com>,
        Emma Anholt <emma@...olt.net>, Daniel Vetter <daniel@...ll.ch>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Dom Cobley <dom@...pberrypi.com>,
        Hans de Goede <hdegoede@...hat.com>,
        linux-arm-kernel@...ts.infradead.org,
        Phil Elwell <phil@...pberrypi.com>,
        intel-gfx@...ts.freedesktop.org,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        nouveau@...ts.freedesktop.org, linux-sunxi@...ts.linux.dev,
        Mateusz Kwiatkowski <kfyatek+publicgit@...il.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Noralf Trønnes <noralf@...nnes.org>
Subject: Re: [PATCH v2 00/41] drm: Analog TV Improvements



Den 05.09.2022 16.57, skrev Maxime Ripard:
> On Fri, Sep 02, 2022 at 01:28:16PM +0200, Noralf Trønnes wrote:
>>
>>
>> Den 01.09.2022 21.35, skrev Noralf Trønnes:
>>>
>>>
>>> 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
>>>
>>
>> It turns out I didn't have to disable runtime pm:
>> https://gist.github.com/notro/0adcfcb12460b54e54458afe11dc8ea2
> 
> If the bcm2711_thermal IP needs that clock to be enabled, it should grab
> a reference itself, but it looks like even the device tree binding
> doesn't ask for one.
> 

The first thing I tried was to unload the bcm2711_thermal module before
running modeset and it still hung, so I don't think that's the problem.

Noralf.