linux-kernel - Re: [PATCH 04/14] wifi: ath10k: snoc: support powering on the device via pwrseq

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Message-ID: <trdxottcptxd5uvgn63oaphemnsk6s2ujc3533abh6pm65iqpi@5ahtn56pff67>
Date: Sat, 3 Jan 2026 01:24:19 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Bartosz Golaszewski <brgl@...nel.org>
Cc: Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Marcel Holtmann <marcel@...tmann.org>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        Jeff Johnson <jjohnson@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Manivannan Sadhasivam <mani@...nel.org>, Vinod Koul <vkoul@...nel.org>,
        Balakrishna Godavarthi <quic_bgodavar@...cinc.com>,
        Matthias Kaehlcke <mka@...omium.org>, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-bluetooth@...r.kernel.org, linux-wireless@...r.kernel.org,
        ath10k@...ts.infradead.org, linux-pm@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>
Subject: Re: [PATCH 04/14] wifi: ath10k: snoc: support powering on the device
 via pwrseq

On Fri, Jan 02, 2026 at 06:06:51PM +0100, Bartosz Golaszewski wrote:
> On Fri, Jan 2, 2026 at 4:10 PM Dmitry Baryshkov
> <dmitry.baryshkov@....qualcomm.com> wrote:
> >
> > On Fri, 2 Jan 2026 at 13:07, Bartosz Golaszewski <brgl@...nel.org> wrote:
> > >
> > > On Wed, Dec 31, 2025 at 12:36 AM Dmitry Baryshkov
> > > <dmitry.baryshkov@....qualcomm.com> wrote:
> > > >
> > > > The WCN39xx family of WiFi/BT chips incorporates a simple PMU, spreading
> > > > voltages over internal rails. Implement support for using powersequencer
> > > > for this family of ATH10k devices in addition to using regulators.
> > > >
> > > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
> > > > ---
> > >
> > > [snip]
> > >
> > > >
> > > >  static void ath10k_snoc_wlan_disable(struct ath10k *ar)
> > > > @@ -1762,7 +1779,27 @@ static int ath10k_snoc_probe(struct platform_device *pdev)
> > > >                 goto err_release_resource;
> > > >         }
> > > >
> > > > -       ar_snoc->num_vregs = ARRAY_SIZE(ath10k_regulators);
> > > > +       /*
> > > > +        * Backwards compatibility, ignore the defer error from pwrseq, if it
> > > > +        * should be used, we will get an error from regulator get.
> > > > +        */
> > >
> > > Can you elaborate on this? I'm not exactly following. I suppose you
> > > mean the regulator_get() will return -EPROBE_DEFER? One of the
> > > supplies exposed by the PMU?
> >
> > Yes. devm_pwrseq_get() can return -EPROBE_DEFER in two cases:
> > - it is not supposed to be used
> > - it is supposed to be used, but the driver hasn't probed yet.
> >
> 
> Yes but normally driver core would still create a devlink between the
> device binding to the PMU node and the consumer of its regulators -

fw_devlink, which are not mandatory, time out, etc. So, no, it is not
granted that the PMU is always available during the probe.

> this device - so we can expect that it will always be the first one,
> no? Unless we need this driver to be firmware-agnostic.
> 
> > There is no simple way to distinguish between these two cases, but:
> > - if it is not supposed to be used, then regulator_bulk_get() will
> > return all regulators as expected, continuing the probe
> > - if it is supposed to be used, but wasn't probed yet, we will get
> > -EPROBE_DEFER from regulator_bulk_get() too.
> >
> > I can write that in a comment, if you think that it makes the code more obvious.
> >
> 
> Yes, please make it more descriptive. Ideally I'd like to improve the
> API to avoid such confusion in the future.

The prolem is that we can't (or I don't see a way to). Power sequencing
core has no way to distinguish these two cases.

-- 
With best wishes
Dmitry