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

From: Konrad Dybcio <konrad.dybcio@linaro.org>
To: Mark Brown <broonie@kernel.org>, Bartosz Golaszewski <brgl@bgdev.pl>
Cc: 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: Tue, 20 Feb 2024 22:21:04 +0100	[thread overview]
Message-ID: <17bbd9ae-0282-430e-947b-e6fb08c53af7@linaro.org> (raw)
In-Reply-To: <ea08a286-ff53-4d58-ae41-38cca151508c@sirena.org.uk>

On 20.02.2024 13:47, Mark Brown wrote:
> On Tue, Feb 20, 2024 at 12:22:42PM +0100, Bartosz Golaszewski wrote:
>> On Mon, Feb 19, 2024 at 6:50 PM Mark Brown <broonie@kernel.org> wrote:
>>> On Fri, Feb 16, 2024 at 09:32:11PM +0100, Bartosz Golaszewski wrote:
> 
>>>> +static struct pci_pwrctl_wcn7850_vreg pci_pwrctl_wcn7850_vregs[] = {
>>>> +     {
>>>> +             .name = "vdd",
>>>> +             .load_uA = 16000,
>>>> +     },
> 
>>> I know a bunch of the QC stuff includes these load numbers but are they
>>> actually doing anything constructive?  It keeps coming up that they're
>>> causing a bunch of work and it's not clear that they have any great
>>> effect on modern systems.
> 
>> Yes, we have what is called a high-power mode and a low-power mode in
>> regulators and these values are used to determine which one to use.
> 
> 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.

Konrad