[Intel-gfx] [PATCH v3 1/2] PCI / PM: Add needs_resume flag to avoid suspend complete optimization

[Rafael J. Wysocki]

On Tuesday, May 02, 2017 12:05:38 PM Imre Deak wrote:
> On Mon, May 01, 2017 at 10:36:13PM +0200, Rafael J. Wysocki wrote:
> > On Sunday, April 30, 2017 03:57:13 PM Imre Deak wrote:
> > > On Sat, Apr 29, 2017 at 12:21:57PM +0200, Rafael J. Wysocki wrote:
> > > > On Friday, April 28, 2017 11:33:02 PM Rafael J. Wysocki wrote:
> > > > > On Friday, April 28, 2017 05:16:02 PM Imre Deak wrote:
> > > > > > Some drivers - like i915 - may not support the system suspend direct
> > > > > > complete optimization due to differences in their runtime and system
> > > > > > suspend sequence. Add a flag that when set resumes the device before
> > > > > > calling the driver's system suspend handlers which effectively disables
> > > > > > the optimization.
> > > > > > 
> > > > > > Needed by the next patch fixing suspend/resume on i915.
> > > > > > 
> > > > > > Suggested by Rafael.
> > > > > > 
> > > > > > Cc: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
> > > > > > Cc: Bjorn Helgaas <bhelgaas at google.com>
> > > > > > Cc: linux-pci at vger.kernel.org
> > > > > > Cc: stable at vger.kernel.org
> > > > > > Signed-off-by: Imre Deak <imre.deak at intel.com>
> > > > > 
> > > > > Acked-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
> > > > > 
> > > > > The reason why the opt-out flag was not added on day one was because we were
> > > > > not sure whether or not it would be necessary at all.
> > > > > 
> > > > > Quite evidently, it is needed.
> > > > 
> > > > But that said, it actually can be implemented as a flag in dev_flags too, say
> > > > PCI_DEV_FLAGS_NEEDS_RESUME, in analogy with PCI_DEV_FLAGS_NO_D3 that's
> > > > already there.
> > > > 
> > > > The struct size would not need to grow then which I guess would be better?
> > > 
> > > Hm, both the bit field and the flag would need to increase if running
> > > out of bits, so what's the difference? (Atm, the struct size wouldn't
> > > change either way.)
> > 
> > In the bit field case this depends on what the compiler thinks is better to be
> > entirely precise, so they are not 100% equivalent.
> > 
> > Plus, since there already are things related to PM in dev_flags, why to depart
> > from that pattern?
> 
> There are a few PM related flags in the bit field too.
> 
> The need for moving it is still not clear to me, but I don't see any
> problem with it either, so will move it there.

Well, we are not too consistent in that respect overall.

Either way works, so I guess it's Bjorn's call at this point. :-)

Thanks,
Rafael