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

[Maxime Ripard]

On Mon, Sep 05, 2022 at 05:17:18PM +0200, Noralf Trønnes wrote:
> 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.

Ack. Just to confirm, is this happening on mainline or on the downstream tree?

Maxime

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