linux-kernel - Re: [PATCH v3 2/2] PCI: qcom: properly implement RC shutdown/power up

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Date: Wed, 27 Mar 2024 22:27:15 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: 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>,
 Marijn Suijten <marijn.suijten@...ainline.org>,
 Bjorn Andersson <quic_bjorande@...cinc.com>
Subject: Re: [PATCH v3 2/2] PCI: qcom: properly implement RC shutdown/power up

On 27.03.2024 10:20 PM, Bjorn Helgaas wrote:
> On Wed, Mar 27, 2024 at 08:49:09PM +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.
>>
>> Implement full shutdown and re-initialization to allow for powering off
>> the controller.
>>
>> This is mainly intended for SC8280XP with a broken power rail setup,
>> which requires a full RC shutdown/reinit in order to reach SoC-wide
>> power collapse, but sleeping is generally better than not sleeping and
>> less destructive suspend can be implemented later for platforms that
>> support it.
> 
> Second try (first at
> https://lore.kernel.org/all/20240212213216.GA1145794@bhelgaas/):
> 
>   - Capitalize subject lines to match history (sorry, I didn't mention
>     the first time)
> 
>   - Drop or replace "properly" with something specific
> 
>   - "... minimizing power draw while keeping RC up at all times ...
>     draws a whole lot of power" doesn't quite make sense to me
> 
>   - Reword or explain "power collapse"
> 
>   - No COMPILE_TEST provision (maybe it turned out to be impractical?)
> 
>   - Magic delay numbers below with no citation or explanation.  Even a
>     short comment could be a hint about how to verify and potentially
>     change in the future.  A #define for readl_poll_timeout() would be
>     helpful as a place for a comment and because the name could
>     include "_US" to show the units.
> 
>   - Add "()" after function names in comments

Sorry Bjorn, I came back to this series after some time and didn't revisit
your message. I'll be sure not to forget the next time around.

Konrad