Re: [PATCH 3/3] PCI: Convert rtw88 power cycle quirk to shutdown quirk

From: Heiner Kallweit <hkallweit1@gmail.com>
To: Kai-Heng Feng <kai.heng.feng@canonical.com>
Cc: Kalle Valo <kvalo@codeaurora.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Yan-Hsuan Chuang <tony0620emma@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	Linux Netdev List <netdev@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>,
	Linux PCI <linux-pci@vger.kernel.org>
Subject: Re: [PATCH 3/3] PCI: Convert rtw88 power cycle quirk to shutdown quirk
Date: Fri, 26 Feb 2021 14:31:31 +0100	[thread overview]
Message-ID: <6db9e75e-52a7-4316-bfd8-cf44b4875f44@gmail.com> (raw)
In-Reply-To: <CAAd53p6tWUn-QbCysL_KweREmpSNfiQa7-gHgndqGta2UWt0=Q@mail.gmail.com>

On 26.02.2021 13:18, Kai-Heng Feng wrote:
> On Fri, Feb 26, 2021 at 8:10 PM Heiner Kallweit <hkallweit1@gmail.com> wrote:
>>
>> On 26.02.2021 08:12, Kalle Valo wrote:
>>> Kai-Heng Feng <kai.heng.feng@canonical.com> writes:
>>>
>>>> Now we have a generic D3 shutdown quirk, so convert the original
>>>> approach to a PCI quirk.
>>>>
>>>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
>>>> ---
>>>>  drivers/net/wireless/realtek/rtw88/pci.c | 2 --
>>>>  drivers/pci/quirks.c                     | 6 ++++++
>>>>  2 files changed, 6 insertions(+), 2 deletions(-)
>>>
>>> It would have been nice to CC linux-wireless also on patches 1-2. I only
>>> saw patch 3 and had to search the rest of patches from lkml.
>>>
>>> I assume this goes via the PCI tree so:
>>>
>>> Acked-by: Kalle Valo <kvalo@codeaurora.org>
>>>
>>
>> To me it looks odd to (mis-)use the quirk mechanism to set a device
>> to D3cold on shutdown. As I see it the quirk mechanism is used to work
>> around certain device misbehavior. And setting a device to a D3
>> state on shutdown is a normal activity, and the shutdown() callback
>> seems to be a good place for it.
>> I miss an explanation what the actual benefit of the change is.
> 
> To make putting device to D3 more generic, as there are more than one
> device need the quirk.
> 
> Here's the discussion:
> https://lore.kernel.org/linux-usb/00de6927-3fa6-a9a3-2d65-2b4d4e8f0012@linux.intel.com/
> 

Thanks for the link. For the AMD USB use case I don't have a strong opinion,
what's considered the better option may be a question of personal taste.
For rtw88 however I'd still consider it over-engineering to replace a simple
call to pci_set_power_state() with a PCI quirk.
I may be biased here because I find it sometimes bothering if I want to
look up how a device is handled and in addition to checking the respective
driver I also have to grep through quirks.c whether there's any special
handling.

> Kai-Heng
> 
Heiner