Re: [PATCH v6 0/4] regulator: qcom-rpmh: Support RPMH address reads and use it for rpmh-regulators

[Kamal Wadhwa]

On Fri, Oct 23, 2026 at 01:18:38PM +0530, Kanishka Chakraborty wrote:
> Hi,
> 
> with this series in v7.3, SM7150 (Snapdragon 732G, Xiaomi Redmi Note 10
> Pro) no longer boots. SM7150 support is not upstream yet; I am running
> v7.3 with the sm7150-mainline patches on top, but the problem looks
> independent of that and may affect other SoCs with older RSCs.
> 
> Symptom: the boot stops around the time the RPMh regulators register.
> The display (left on by the bootloader) goes grey at that point and the
> initramfs never runs, while the kernel apparently keeps running (the
> watchdog keeps being serviced). The v7.1-based sm7150-mainline tree
> boots fine on the same device with the same DT.
> 
> What I checked:
> 
> - Reverting 09d99ff7fc3c ("regulator: qcom-rpmh: readback
>   voltage/bypass/mode set during bootup") and its follow-up 216e8873bc80
>   ("regulator: qcom-rpmh: Fix coding style issues") makes v7.3 boot.
> 
> - A log-only variant that still issues every rpmh_read() but throws the
>   results away (vreg->mode, bypassed and voltage_selector restored to the
>   pre-readback defaults) hangs exactly the same way. So issuing the reads
>   is enough to break it, independent of what is done with the values.
>   I couldn't capture the per-read log lines: the display dies at that
>   point and the boot never gets far enough for USB or a log.
> 
> - The apps RSC here reports RSC_DRV_ID = 0x00010100, i.e. version 1.1.
>   rpmh-rsc only describes the v2.7 and v3.0 register layouts and uses the
>   v2.7 one for everything below 3.0, so on this RSC the read path writes
>   CMD_MSGID without the write bit and later reads RESP_DATA at the v2.7
>   offset. This SoC has two active-only TCSes.
> 
> I don't know whether read requests are supported on RSC v1.x at all, or
> only need a different register layout there. Would it make sense to only
> issue reads on RSCs known to support them, and let rpmh_read() return
> -EOPNOTSUPP otherwise, so the regulator driver falls back to the old
> behaviour?
> 
> I'm happy to test patches or collect more data on this device.

Hi Kanishka,

Thanks for your test results!  Maulik shah has added a new patch series
https://lore.kernel.org/all/20260911-rsc_read-v2-0-98675c248278@xxxxxxxxxxxxxxxx/
to address this problem, it seems he also recieved a suggestion to fix it in
the way you suggested to have the -ENOTSUPP for the platforms which do not
support the reads.

Regards,
Kamal

> 
> Thanks,
> Kanishka