[PATCH v4 06/11] PCI/ASPM: Clear aspm_disable as part of __pci_enable_link_state()

[Krishna Chaitanya Chundru]

On 7/9/2025 2:40 PM, Ilpo Järvinen wrote:
> On Tue, 8 Jul 2025, Manivannan Sadhasivam wrote:
> 
>> On Mon, Jun 09, 2025 at 04:21:27PM GMT, Krishna Chaitanya Chundru wrote:
>>> ASPM states are not being enabled back with pci_enable_link_state() when
>>> they are disabled by pci_disable_link_state(). This is because of the
>>> aspm_disable flag is not getting cleared in pci_enable_link_state(), this
>>> flag is being properly cleared when ASPM is controlled by sysfs.
>>>
>>
>> A comment in pcie_config_aspm_link() says:
>>
>>   /* Enable only the states that were not explicitly disabled */
>>
>> But the function is called from both aspm_attr_store_common() and
>> __pci_enable_link_state(). So I don't know if this is behavior is intentional
>> or wrong.
> 
> Hi,
> 
> I think it's intentional. Whether the behavior is useful is another good
> question but the current behavior aligns with the explanation in the
> comment.
> 
> My understanding of the situation is:
> 
> pci_disable_link_state() and pci_enable_link_state() are not symmetric
> despite the names, never have been (this is one of those many quirks ASPM
> driver has which should be eventually cleaned up, IMO).
> 
> It might be appropriate to rename pci_enable_link_state() to
> pci_set_default_link_state() to match the name to its functionality (and
> the function comment):
> 
>   * pci_enable_link_state - Clear and set the default device link state
> 
> Note: "the default ... link state".
> 
> 
> I've already raised this concern earlier! As you see, my comment are
> not getting addressed. I'd like to see the author does one of these:
> 
Hi llpo,

I replied to your comment on v3 patch[1], and I feel instead of having
new function() we can use same API to our purpose.
> 1) Renames pci_enable_link_state() to pci_set_default_link_state()
> 
> 1b) If pci_enable_link_state() is still needed after that, a new function
> is added to symmetrically pair with pci_disable_link_state().
> 
> or alternatively,
> 
> 2) Changelog justifies very clearly why this change is okay with the
> existing callers. (And obviously the function comment should be altered to
> match the functionality in that case too).
> 
> If approach 2 is chosen, it should be very carefully reviewed when it
> comes to the callers.
>
I am in favor of approach 2 which you suggested, but lets wait for other
reviewers feedback on this. Based up on the response i will make
necessary changes in v5.

[1] 
https://lore.kernel.org/all/b3d818f5-942c-1761-221d-af7d7e8f3624@oss.qualcomm.com/

- Krishna Chaitanya.
> 
>>> Clear the aspm_disable flag with the requested ASPM states requested by
>>> pci_enable_link_state().
>>>
>>> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru at oss.qualcomm.com>
>>
>> Fixes tag?
>>
>> - Mani
>>
>>> ---
>>>   drivers/pci/pcie/aspm.c | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
>>> index 94324fc0d3e650cd3ca2c0bb8c1895ca7e647b9d..0f858ef86111b43328bc7db01e6493ce67178458 100644
>>> --- a/drivers/pci/pcie/aspm.c
>>> +++ b/drivers/pci/pcie/aspm.c
>>> @@ -1453,6 +1453,7 @@ static int __pci_enable_link_state(struct pci_dev *pdev, int state, bool locked)
>>>   		down_read(&pci_bus_sem);
>>>   	mutex_lock(&aspm_lock);
>>>   	link->aspm_default = pci_calc_aspm_enable_mask(state);
>>> +	link->aspm_disable &= ~state;
>>>   	pcie_config_aspm_link(link, policy_to_aspm_state(link));
>>>   
>>>   	link->clkpm_default = (state & PCIE_LINK_STATE_CLKPM) ? 1 : 0;
>>>
>>> -- 
>>> 2.34.1
>>>
>>
>>
>