linux-kernel - Re: [PATCH v2 3/3] PCI: qcom: properly implement RC shutdown/power up

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Date: Thu, 15 Feb 2024 11:22:36 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Johan Hovold <johan@...nel.org>
Cc: Bjorn Helgaas <helgaas@...nel.org>, Bjorn Andersson
 <andersson@...nel.org>,
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Krzysztof Wilczyński <kw@...ux.com>,
 Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
 Philipp Zabel <p.zabel@...gutronix.de>, linux-arm-msm@...r.kernel.org,
 linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
 Johan Hovold <johan+linaro@...nel.org>,
 Bjorn Andersson <quic_bjorande@...cinc.com>
Subject: Re: [PATCH v2 3/3] PCI: qcom: properly implement RC shutdown/power up

On 15.02.2024 08:13, Johan Hovold wrote:
> On Wed, Feb 14, 2024 at 10:33:19PM +0100, Konrad Dybcio wrote:
>> On 12.02.2024 22:32, Bjorn Helgaas wrote:
>>> "Properly" is a noise word that suggests "we're doing it right this
>>> time" but doesn't hint at what actually makes this better.
>>>
>>> On Sat, Feb 10, 2024 at 06:10:07PM +0100, Konrad Dybcio wrote:
>>>> Currently, we've only been minimizing the power draw while keeping the
>>>> RC up at all times. This is suboptimal, as it draws a whole lot of power
>>>> and prevents the SoC from power collapsing.
>>>
>>> Is "power collapse" a technical term specific to this device, or is
>>> there some more common term that could be used?  I assume the fact
>>> that the RC remains powered precludes some lower power state of the
>>> entire SoC?
>>
>> That's spot on, "power collapse" commonly refers to shutting down as many
>> parts of the SoC as possible, in order to achieve miliwatt-order power draw.
> 
> I'm pretty sure "power collapse" is a Qualcomm:ism so better to use
> common terminology as Bjorn suggested, and maybe put the Qualcomm
> wording in parenthesis or similar.

Ok, I keep hearing it so much that I had previously assumed it's the
standard way of describing it.. I'll reword this.

Konrad