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

[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.

Maxime
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