linux-kernel - Re: [PATCH 3/3] arm64: dts: qcom: x1e80100-qcp: Add WiFi/BT pwrseq

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Message-ID: <Zwj539cN2DJ7nd3A@linaro.org>
Date: Fri, 11 Oct 2024 12:11:43 +0200
From: Stephan Gerhold <stephan.gerhold@...aro.org>
To: Johan Hovold <johan@...nel.org>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Abel Vesa <abel.vesa@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: Re: [PATCH 3/3] arm64: dts: qcom: x1e80100-qcp: Add WiFi/BT pwrseq

On Thu, Oct 10, 2024 at 11:34:44AM +0200, Johan Hovold wrote:
> On Mon, Oct 07, 2024 at 08:22:27PM +0200, Stephan Gerhold wrote:
> > Add the WiFi/BT nodes for QCP and describe the regulators for the WCN7850
> > combo chip using the new power sequencing bindings. All voltages are
> > derived from chained fixed regulators controlled using a single GPIO.
> > 
> > The same setup also works for CRD (and likely most of the other X1E80100
> > laptops). However, unlike the QCP they use soldered or removable M.2 cards
> > supplied by a single 3.3V fixed regulator. The other necessary voltages are
> > then derived inside the M.2 card. Describing this properly requires
> > new bindings, so this commit only adds QCP for now.
> 
> Based on our discussions it seems we do not really need to describe the
> internal PMU at all for WCN7850 (as the bluetooth and wlan blocks can be
> enabled indepdendently) so perhaps we can just restore the old binding
> and drop most of this boilerplate for all boards.
> 

I think there is no clear conclusion on that yet. The old bindings
didn't describe any power supplies for WiFi at all. The pwrseq bindings
are currently the only way to do that.

We could potentially move all the "PMU supplies" to the WiFi/BT nodes
and rely on reference counting to handle them. But I think it's better
to wait how the M.2/generic PCI power control discussion turns out
before investing any time to refactor the current solution.

There are existing users of qcom,wcn7850-pmu already in 6.11, so I think
it does not hurt to take this patch as-is for now. We can clean them up
together later if needed.

Thanks,
Stephan