linux-kernel - Re: [RESEND PATCH 0/2] Add pinctrl_pm_select_init

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Message-ID: <cb76e0da-f4c9-4aaf-8e0b-4666738d238e@foss.st.com>
Date: Thu, 7 Aug 2025 16:15:39 +0200
From: Christian Bruel <christian.bruel@...s.st.com>
To: Bjorn Helgaas <helgaas@...nel.org>,
        Linus Walleij
	<linus.walleij@...aro.org>
CC: <lpieralisi@...nel.org>, <kwilczynski@...nel.org>, <mani@...nel.org>,
        <robh@...nel.org>, <bhelgaas@...gle.com>, <mcoquelin.stm32@...il.com>,
        <alexandre.torgue@...s.st.com>, <linux-pci@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linux-gpio@...r.kernel.org>
Subject: Re: [RESEND PATCH 0/2] Add pinctrl_pm_select_init_state helper
 function

Gentle ping,

Maybe the best for Linus is to apply only 1/2 on his pinctrl tree.

I'll rebase 2/2 stm32 PCIe part after the merge to mainline and respin 
for the PCI tree

Best Regards

Christian

On 7/24/25 15:36, Christian Bruel wrote:
> 
> 
> On 7/23/25 23:07, Bjorn Helgaas wrote:
>> On Wed, Jul 23, 2025 at 01:32:52PM +0200, Linus Walleij wrote:
>>> On Thu, Jul 17, 2025 at 8:33 AM Christian Bruel
>>> <christian.bruel@...s.st.com> wrote:
>>>
>>>> We have the helper functions pinctrl_pm_select_default_state and
>>>> pinctrl_pm_select_sleep_state.
>>>> This patch adds the missing pinctrl_pm_select_init_state function.
>>>>
>>>> The STM32MP2 needs to set the pinctrl to an initial state during
>>>> pm_resume, just like in probe. To achieve this, the function
>>>> pinctrl_pm_select_init_state is added.
>>>>
>>>> This allows a driver to balance pinctrl_pm_select_sleep_state()
>>>> with pinctrl_pm_select_default_state() and
>>>> pinctrl_pm_select_init_state() in pm_runtime_suspend and 
>>>> pm_runtime_resume.
>>>>
>>>> Christian Bruel (2):
>>>>    pinctrl: Add pinctrl_pm_select_init_state helper function
>>>>    PCI: stm32: use pinctrl_pm_select_init_state() in
>>>>      stm32_pcie_resume_noirq()
>>>
>>> If Bjorn Helgaas is OK with it I can apply this to the pinctrl tree.
>>>
>>> Otherwise I can also just apply patch 1/2, but that doesn't solve
>>> any problem.
>>
>> The stm32 driver has been posted and is on this branch of the PCI
>> tree:
>>
>>    https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/log/? 
>> h=controller/dwc-stm32&id=5a972a01e24b
>>
>> but it's not in mainline (or even in pci/next) yet, so you would only
>> be able to apply patch 2/2 if you took the whole driver, which is
>> probably more than you would want to do.
>>
>> I haven't put it in pci/next yet because it doesn't build when
>> CONFIG_PINCTRL is not defined:
>>
>>    https://lore.kernel.org/r/20250716192418.GA2550861@bhelgaas
>>
>> I don't know enough about pinctrl to know why stm32 needs this when
>> nobody else seems to.  I doubt it's really unique, so maybe it's just
>> not doing the right thing here.
> 
> The STM32MP2 is unique because the core clock is gated on CLKREQ#. 
> Consequently, it is not possible to access the core registers from DBI 
> when no card is attached, causing the board to freeze. I don't know 
> another platform with this limitation
> 
> To fix this, we use a GPIO to de-assert CLKREQ# during probe and restore 
> the pin to its default AF mode afterward. This works perfectly for 
> probe, but we lack functionality for PM resume unless we explicitly 
> select the state with pinctrl_pm_select_XXX_state().
> 
> For reference, the init_state functionality was introduced in
> https://lkml.org/lkml/2015/10/21/1
> 
> If we prefer not to extend the pinctrl API in patch 1/2, I can fix the 
> case in patch 2/2 only with something like:
> 
> in stm32_pcie_probe()
>       pinctrl = devm_pinctrl_get(dev);
> 
>       if(pinctrl!= -ENODEV) // PINCTRL is defined
>            pinctrl_init = pinctrl_lookup_state(stm32_pcie>pinctrl, 
> PINCTRL_STATE_IN
> 
> in stm32_pcie_resume_noirq()
>     if (pinctrl) {
>            ret = pinctrl_select_state(stm32_pcie->pinctrl, stm32_pcie- 
>  >pinctrl_init);
> 
> What do you advise ?
> 
> thank you
> 
> Christian
> 
> 
> 
>>
>> Bjorn
>