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

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Date: Tue, 20 Feb 2024 22:21:04 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Mark Brown <broonie@...nel.org>, Bartosz Golaszewski <brgl@...ev.pl>
Cc: Marcel Holtmann <marcel@...tmann.org>,
 Luiz Augusto von Dentz <luiz.dentz@...il.com>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Kalle Valo <kvalo@...nel.org>,
 Bjorn Andersson <andersson@...nel.org>, Liam Girdwood <lgirdwood@...il.com>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Bjorn Helgaas <bhelgaas@...gle.com>, Saravana Kannan <saravanak@...gle.com>,
 Geert Uytterhoeven <geert+renesas@...der.be>, Arnd Bergmann <arnd@...db.de>,
 Neil Armstrong <neil.armstrong@...aro.org>,
 Marek Szyprowski <m.szyprowski@...sung.com>, Alex Elder <elder@...aro.org>,
 Srini Kandagatla <srinivas.kandagatla@...aro.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Abel Vesa <abel.vesa@...aro.org>, Manivannan Sadhasivam <mani@...nel.org>,
 Lukas Wunner <lukas@...ner.de>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-wireless@...r.kernel.org, linux-arm-msm@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-pci@...r.kernel.org,
 linux-pm@...r.kernel.org,
 Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v5 14/18] PCI/pwrctl: add a power control driver for
 WCN7850

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@...nel.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