Re: [PATCH] soc: qcom: mark pd-mapper as broken

[Stephan Gerhold <stephan.gerhold@linaro.org>]

On Thu, Oct 10, 2024 at 09:42:46AM +0200, Johan Hovold wrote:
> When using the in-kernel pd-mapper on x1e80100, client drivers often
> fail to communicate with the firmware during boot, which specifically
> breaks battery and USB-C altmode notifications. This has been observed
> to happen on almost every second boot (41%) but likely depends on probe
> order:
> 
>     pmic_glink_altmode.pmic_glink_altmode pmic_glink.altmode.0: failed to send altmode request: 0x10 (-125)
>     pmic_glink_altmode.pmic_glink_altmode pmic_glink.altmode.0: failed to request altmode notifications: -125
> 
>     ucsi_glink.pmic_glink_ucsi pmic_glink.ucsi.0: failed to send UCSI read request: -125
> 
>     qcom_battmgr.pmic_glink_power_supply pmic_glink.power-supply.0: failed to request power notifications
> 
> In the same setup audio also fails to probe albeit much more rarely:
> 
>     PDR: avs/audio get domain list txn wait failed: -110
>     PDR: service lookup for avs/audio failed: -110
> 
> Chris Lew has provided an analysis and is working on a fix for the
> ECANCELED (125) errors, but it is not yet clear whether this will also
> address the audio regression.
> 
> Even if this was first observed on x1e80100 there is currently no reason
> to believe that these issues are specific to that platform.
> 
> Disable the in-kernel pd-mapper for now, and make sure to backport this
> to stable to prevent users and distros from migrating away from the
> user-space service.
> 
> Fixes: 1ebcde047c54 ("soc: qcom: add pd-mapper implementation")
> Cc: stable@vger.kernel.org	# 6.11
> Link: https://lore.kernel.org/lkml/Zqet8iInnDhnxkT9@hovoldconsulting.com/
> Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
> ---
> 
> It's now been over two months since I reported this regression, and even
> if we seem to be making some progress on at least some of these issues I
> think we need disable the pd-mapper temporarily until the fixes are in
> place (e.g. to prevent distros from dropping the user-space service).
> 

This is just a random thought, but I wonder if we could insert a delay
somewhere as temporary workaround to make the in-kernel pd-mapper more
reliable. I just tried replicating the userspace pd-mapper timing on
X1E80100 CRD by:

 1. Disabling auto-loading of qcom_pd_mapper
    (modprobe.blacklist=qcom_pd_mapper)
 2. Adding a systemd service that does nothing except running
    "modprobe qcom_pd_mapper" at the same point in time where the 
    userspace pd-mapper would usually be started.

This seems to work quite well for me, I haven't seen any of the
mentioned errors anymore in a couple of boot tests. Clearly, there is no
actual bug in the in-kernel pd-mapper, only worse timing.

Thanks,
Stephan