Re: [PATCH] dt-bindings: mmc: Add cap-aggressive-pm property

[Krzysztof Kozlowski]

On 02/02/2023 15:59, Ulf Hansson wrote:
> On Tue, 31 Jan 2023 at 17:57, Krzysztof Kozlowski
> <krzysztof.kozlowski@xxxxxxxxxx> wrote:
>>
>> On 30/01/2023 07:54, Hermes Zhang wrote:
>>> On 2023/1/29 18:58, Krzysztof Kozlowski wrote:
>>>> On 29/01/2023 03:36, Hermes Zhang wrote:
>>>>> This commit add a new property: cap-aggressive-pm to enable the
>>>> Do not use "This commit/patch".
>>>> https://elixir.bootlin.com/linux/v5.17.1/source/Documentation/process/submitting-patches.rst#L95
>>>
>>> Done
>>>
>>>>> MMC_CAP_AGGRESSIVE_PM feature for (e)MMC/SD power saving.
>>>> Why this is a property suitable for DT? IOW, why this isn't enabled always?
>>>
>>> This property will benfit for the power consumption, but it also may
>>> degradation in performance as it will prevent the
>>>
>>> the card from executing internal house-keeping operations in idle mode.
>>> So it's better to config it from DT.
>>
>> Why? DT is not for policy. How you described it, this is policy or
>> system tuning choice thus the job for Linux (OS), not for DT. So I will
>> repeat - why this property fits the purpose of DT (describe the hardware).
>>
> 
> I guess the HW perspective here, is that it might not fit all
> platforms nor the actual eMMC/SD card to support this feature.
> However, it still seems like a policy rather than a strict HW
> constraint.
> 
> Perhaps there is a way to figure out in the host driver, to
> conditionally set the MMC_CAP_AGGRESSIVE_PM for the host, when needed
> instead?

What also worries me is that there is no user of this property: no DTS,
no driver, so it is tricky to deduct out when it is applicable.

Anyway things which might be obvious for the submitter, might not be for
the reviewer, thus I would really like to see justification why
different boards (or memories) need this property.

Best regards,
Krzysztof