[+cc Rafael, linux-pm] On Thu, Mar 04, 2021 at 02:07:18PM +0800, Kai-Heng Feng wrote: > On Sat, Feb 27, 2021 at 2:17 AM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > On Fri, Feb 26, 2021 at 02:31:31PM +0100, Heiner Kallweit wrote: > > > On 26.02.2021 13:18, Kai-Heng Feng wrote: > > > > On Fri, Feb 26, 2021 at 8:10 PM Heiner Kallweit <hkallweit1@xxxxxxxxx> wrote: > > > >> > > > >> On 26.02.2021 08:12, Kalle Valo wrote: > > > >>> Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx> > > > >>>> --- > > > >>>> 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@xxxxxxxxxxxxxx> > > > >> > > > >> 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@xxxxxxxxxxxxxxx/ > > > > > > > > > > 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. > > > > I haven't looked at these patches carefully, but in general, I agree > > that quirks should be used to work around hardware defects in the > > device. If the device behaves correctly per spec, we should use a > > different mechanism so the code remains generic and all devices get > > the benefit. > > > > If we do add quirks, the commit log should explain what the device > > defect is. > > So maybe it's reasonable to put all PCI devices to D3 at shutdown? I don't know off-hand. I added Rafael and linux-pm in case they do. If not, I suggest working up a patch to do that and a commit log that explains why that's a good idea and then we can have a discussion about it. This thread really doesn't have that justification. It says "putting device X in D3cold at shutdown saves 0.03w while in S5", but doesn't explain why that's safe or desirable for all devices. Bjorn
