Re: [PATCH v5 14/18] PCI/pwrctl: add a power control driver for WCN7850

From: Bartosz Golaszewski <brgl@bgdev.pl>
To: Mark Brown <broonie@kernel.org>
Cc: Konrad Dybcio <konrad.dybcio@linaro.org>,
	Marcel Holtmann <marcel@holtmann.org>,
	 Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
	"David S . Miller" <davem@davemloft.net>,
	 Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	 Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	 Conor Dooley <conor+dt@kernel.org>,
	Kalle Valo <kvalo@kernel.org>,
	 Bjorn Andersson <andersson@kernel.org>,
	Liam Girdwood <lgirdwood@gmail.com>,
	 Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	 Bjorn Helgaas <bhelgaas@google.com>,
	Saravana Kannan <saravanak@google.com>,
	 Geert Uytterhoeven <geert+renesas@glider.be>,
	Arnd Bergmann <arnd@arndb.de>,
	 Neil Armstrong <neil.armstrong@linaro.org>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	 Alex Elder <elder@linaro.org>,
	Srini Kandagatla <srinivas.kandagatla@linaro.org>,
	 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Abel Vesa <abel.vesa@linaro.org>,
	 Manivannan Sadhasivam <mani@kernel.org>,
	Lukas Wunner <lukas@wunner.de>,
	 Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
	linux-bluetooth@vger.kernel.org,  netdev@vger.kernel.org,
	devicetree@vger.kernel.org,  linux-kernel@vger.kernel.org,
	linux-wireless@vger.kernel.org,  linux-arm-msm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,  linux-pci@vger.kernel.org,
	linux-pm@vger.kernel.org,
	 Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Subject: Re: [PATCH v5 14/18] PCI/pwrctl: add a power control driver for WCN7850
Date: Thu, 22 Feb 2024 10:22:50 +0100	[thread overview]
Message-ID: <CAMRc=MedCX_TGGawMhr39oXtJPF4pOQF=Jh2z4uXkOxwhfJWRw@mail.gmail.com> (raw)
In-Reply-To: <53f0956f-ee64-4bd6-b44f-cbebafd42e46@sirena.org.uk>

On Wed, Feb 21, 2024 at 12:44 AM Mark Brown <broonie@kernel.org> wrote:
>
> On Tue, Feb 20, 2024 at 10:21:04PM +0100, Konrad Dybcio wrote:
> > On 20.02.2024 13:47, Mark Brown wrote:
>
> > > Are you *sure* this actually happens (and that the regulators don't
> > > figure it out by themselves), especially given that the consumers are
> > > just specifying the load once rather than varying it dynamically at
> > > runtime which is supposed to be the use case for this API?  This API is
> > > intended to be used dynamically, if the regulator always needs to be in
> > > a particular mode just configure that statically.
>
> > *AFAIU*
>
> > The regulators aggregate the requested current (there may be
> > multiple consumers) and then it's decided if it's high enough
> > to jump into HPM.
>
> Yes, that's the theory - I just question if it actually does something
> useful in practice.  Between regulators getting more and more able to
> figure out mode switching autonomously based on load monitoring and them
> getting more efficient it's become very unclear if this actually
> accomplishes anything, the only usage is the Qualcomm stuff and that's
> all really unsophisticated and has an air of something that's being
> cut'n'pasted forwards rather than delivering practical results.  There
> is some value at ultra low loads, but that's more for suspend modes than
> for actual use.

Removing it would be out of scope for this series and I don't really
want to introduce any undefined behavior when doing a big development
like that. I'll think about it separately.

Bart