[alsa-devel] [PATCH v2] ASoC: max98090: save and restore SHDN when changing sensitive registers

[Mark Brown]

On Thu, Dec 19, 2019 at 09:03:42AM +0100, Marek Szyprowski wrote:
> On 18.12.2019 17:24, Mark Brown wrote:

> I've checked again the exact probe order and here is what happens in the 
> system:

> 1. first call to odroid_audio_probe() is just after:
> 
> [    2.942428] samsung-i2s 3830000.i2s-sec: DMA channels sourced from device 3830000.i2s

> 2. That time, i2s dai and max98090 devices are already registered. 
> However the snd_soc_of_get_dai_link_codecs() return -EPROBE_DEFER, 
> because it cannot get the HDMI codec component.

> 3. HDMI codec is being registered when Exynos DRM initializes. This 
> happens later:

> [    3.127833] [drm] Initialized exynos 1.1.0 20180330 for exynos-drm on 
> minor 0

> 4. Then odroid_audio_probe() is called again from the deferred probe 
> worker and succeeds:

> [    3.501198] ALSA device list:
> [    3.501300]   #0: Odroid-U3

> 5. Then userspace starts:

> [    3.603825] Run /sbin/init as init process
> 
> 6. when userspace init scripts (alsactl) enumerates devices in the 
> system the lockdep warning is triggered:
> 
> [   10.068990] ======================================================
> [   10.070970] WARNING: possible circular locking dependency detected
> [   10.077136] 5.5.0-rc2-next-20191218 #7188 Not tainted
> [   10.082168] ------------------------------------------------------
> [   10.088332] alsactl/1106 is trying to acquire lock:
> 
> 7. then alsa utils probably tries to load the saved values for the controls, what triggers the NULL ptr dereference:
> 
> [....] Setting up ALSA...[   10.502672] 8<--- cut here ---
> [   10.502772] Unable to handle kernel NULL pointer dereference at virtual address 000000b0

OK, so this is probably related to some of Morimoto-san's bisections.
Is there any chance you coudld do a bisect to try to isolate where
things go wrong?
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