linux-kernel - Re: [PATCH v3 2/7] regulator: qca6390: add support for QCA639x powerup sequence

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Message-ID: <20210622143812.GE4574@sirena.org.uk>
Date:   Tue, 22 Jun 2021 15:38:12 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@...r.kernel.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-bluetooth@...r.kernel.org
Subject: Re: [PATCH v3 2/7] regulator: qca6390: add support for QCA639x
 powerup sequence

On Tue, Jun 22, 2021 at 05:17:28PM +0300, Dmitry Baryshkov wrote:
> On Tue, 22 Jun 2021 at 14:29, Mark Brown <broonie@...nel.org> wrote:
> > On Tue, Jun 22, 2021 at 01:31:36AM +0300, Dmitry Baryshkov wrote:

> > > Qualcomm QCA6390/1 is a family of WiFi + Bluetooth SoCs, with BT part
> > > being controlled through the UART and WiFi being present on PCIe
> > > bus. Both blocks share common power sources. Add device driver handling
> > > power sequencing of QCA6390/1.

> > Are you sure this is a regulator and not a MFD?  It appears to be a
> > consumer driver that turns on and off a bunch of regulators en masse
> > which for some reason exposes that on/off control as a single supply.
> > This looks like it'd be much more appropriate to implement as a MFD or
> > possibly power domain with the subdevices using runtime PM, it's clearly
> > not a regulator.

> First attempt was designed to be an MFD. And Lee clearly stated that
> this is wrong:
> "This is not an MFD, since it utilised neither the MFD API nor
> of_platform_populate() to register child devices." [1]

Well, perhaps it should do one of those things then?  Like I say this is
very clearly not a regulator, it looks like a consumer of some kind.
The regulator API isn't there just to absorb things that need reference
counting, it's there to represent things providing supplies.  This seems
to be very clearly not a supply given that it's grouping together a
bunch of other supplies and switching them on and off together without
providing a clear output supply.

> I've tried following Rob's suggestions on implementing things clearly,
> but doing so results in too big restructure just for a single device.

I don't know what that suggestion was?  If there's only one device that
uses this why is it not implemented as part of that device?

> > > +static int qca6390_enable(struct regulator_dev *rdev)
> > > +{
> > > +     struct qca6390_data *data = rdev_get_drvdata(rdev);
> > > +     int ret;

> > > +     ret = regulator_bulk_enable(data->num_vregs, data->regulators);
> > > +     if (ret) {
> > > +             dev_err(data->dev, "Failed to enable regulators");
> > > +             return ret;
> > > +     }

> > The regulator API is *not* recursive, I am astonished this works.

> It does, even with lockdep enabled. Moreover BT regularly does disable
> and enable this regulator, so both enable and disable paths were well
> tested.
> Should I change this into some internal call to remove API recursiveness?

You should not be implementing this as a regulator at all.

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