Re: [PATCH 0/7] clk: qcom: gcc: Do not turn off PCIe GDSCs during gdsc_disable()

[Konrad Dybcio]

On 1/2/26 2:19 PM, Krishna Chaitanya Chundru wrote:
> 
> 
> On 1/2/2026 5:09 PM, Konrad Dybcio wrote:
>> On 1/2/26 12:36 PM, Krishna Chaitanya Chundru wrote:
>>>
>>> On 1/2/2026 5:04 PM, Konrad Dybcio wrote:
>>>> On 1/2/26 10:43 AM, Krishna Chaitanya Chundru wrote:
>>>>> With PWRSTS_OFF_ON, PCIe GDSCs are turned off during gdsc_disable(). This
>>>>> can happen during scenarios such as system suspend and breaks the resume
>>>>> of PCIe controllers from suspend.
>>>> Isn't turning the GDSCs off what we want though? At least during system
>>>> suspend?
>>> If we are keeping link in D3cold it makes sense, but currently we are not keeping in D3cold
>>> so we don't expect them to get off.
>> Since we seem to be tackling that in parallel, it seems to make sense
>> that adding a mechanism to let the PCIe driver select "on" vs "ret" vs
>> "off" could be useful for us
> At least I am not aware of such API where we can tell genpd not to turn off gdsc
> at runtime if we are keeping the device in D3cold state.
> But anyway the PCIe gdsc supports Retention, in that case adding this flag here makes
> more sense as it represents HW.
> sm8450,sm8650 also had similar problem which are fixed by mani[1].

Perhaps I should ask for a clarification - is retention superior to
powering the GDSC off? Does it have any power costs?

>> FWIW I recall I could turn off the GDSCs on at least makena with the old
>> suspend patches and the controllers would come back to life afterwards
> In the suspend patches, we are keeping link in D3cold, so turning off gdsc will not have any effect.

What do you mean by it won't have any effect?

> But if some reason we skipped D3cold like in S2idle case then gdsc should not be off, in that case
> in resume PCIe link will be broken.

Right, obviously

Konrad