Re: [PATCH v2 1/4] drm/i915/dp: Assume panel power is off if runtime suspended

[Imre Deak <imre.deak@intel.com>]

On Wed, Oct 09, 2024 at 11:35:56PM +0300, Cavitt, Jonathan wrote:
> -----Original Message-----
> From: Intel-xe <intel-xe-bounces@lists.freedesktop.org> On Behalf Of Imre Deak
> Sent: Wednesday, October 9, 2024 12:44 PM
> To: intel-xe@lists.freedesktop.org; intel-gfx@lists.freedesktop.org
> Subject: [PATCH v2 1/4] drm/i915/dp: Assume panel power is off if runtime suspended
> >
> > If the device is runtime suspended the eDP panel power is also off.
> > Ignore a short HPD on eDP if the device is suspended accordingly,
> > instead of checking the panel power state via the PPS registers for the
> > same purpose. The latter involves runtime resuming the device
> > unnecessarily, in a frequent scenario where the panel generates a
> > spurious short HPD after disabling the panel power and the device is
> > runtime suspended.
> >
> > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_dp.c                   | 5 ++++-
> >  drivers/gpu/drm/i915/intel_runtime_pm.h                   | 8 +++++++-
> >  drivers/gpu/drm/xe/compat-i915-headers/intel_runtime_pm.h | 8 ++++++++
> >  3 files changed, 19 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> > index fbb096be02ade..3eff35dd59b8a 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -85,6 +85,7 @@
> >  #include "intel_pch_display.h"
> >  #include "intel_pps.h"
> >  #include "intel_psr.h"
> > +#include "intel_runtime_pm.h"
> >  #include "intel_quirks.h"
> >  #include "intel_tc.h"
> >  #include "intel_vdsc.h"
> > @@ -6054,7 +6055,9 @@ intel_dp_hpd_pulse(struct intel_digital_port *dig_port, bool long_hpd)
> >       u8 dpcd[DP_RECEIVER_CAP_SIZE];
> >
> >       if (dig_port->base.type == INTEL_OUTPUT_EDP &&
> > -         (long_hpd || !intel_pps_have_panel_power_or_vdd(intel_dp))) {
> > +         (long_hpd ||
> > +          intel_runtime_pm_suspended(&i915->runtime_pm) ||
> > +          !intel_pps_have_panel_power_or_vdd(intel_dp))) {
> 
> From what I'm reading, I'm fairly certain that
> "i915->runtime_pm->kdev" is equivalent to "i915->drm.dev".
> At least, this seems to be the case according to this comment on
> the intel_runtime_pm struct in intel_runtime_pm.h:
> 
> "       struct device *kdev; /* points to i915->drm.dev */"
> 
> So, "intel_runtime_pm_suspended(&i915->runtime_pm)" seems
> to be logically equivalent to
> "pm_runtime_suspended(i915->drm.dev)", which would mean we
> wouldn't need to declare the new helper function
> "intel_runtime_pm_suspended" as both want to operate
> pm_runtime_suspended on the same relative path for their target
> drm device.
> 
> Though, perhaps I'm missing some other reasons we would want
> the additional helper function besides,

Yes, I was surprised too but drivers/gpu/drm/i915/intel_runtime_pm.h is
not included by xe, even when drivers/gpu/drm/i915/display is built for
it. IIUC for this and other headers the xe specific ones will be
included instead from drivers/gpu/drm/xe/compat-i915-headers. Some of
these in turn like i915_irq.h will revert back including the original
one from drivers/gpu/drm/i915.

> so I won't block on this:
> 
> Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
> -Jonathan Cavitt
> 
> >               /*
> >                * vdd off can generate a long/short pulse on eDP which
> >                * would require vdd on to handle it, and thus we
> > diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.h b/drivers/gpu/drm/i915/intel_runtime_pm.h
> > index 126f8320f86eb..e22669d61e954 100644
> > --- a/drivers/gpu/drm/i915/intel_runtime_pm.h
> > +++ b/drivers/gpu/drm/i915/intel_runtime_pm.h
> > @@ -96,10 +96,16 @@ intel_rpm_wakelock_count(int wakeref_count)
> >       return wakeref_count >> INTEL_RPM_WAKELOCK_SHIFT;
> >  }
> >
> > +static inline bool
> > +intel_runtime_pm_suspended(struct intel_runtime_pm *rpm)
> > +{
> > +     return pm_runtime_suspended(rpm->kdev);
> > +}
> > +
> >  static inline void
> >  assert_rpm_device_not_suspended(struct intel_runtime_pm *rpm)
> >  {
> > -     WARN_ONCE(pm_runtime_suspended(rpm->kdev),
> > +     WARN_ONCE(intel_runtime_pm_suspended(rpm),
> >                 "Device suspended during HW access\n");
> >  }
> >
> > diff --git a/drivers/gpu/drm/xe/compat-i915-headers/intel_runtime_pm.h b/drivers/gpu/drm/xe/compat-i915-headers/intel_runtime_pm.h
> > index cba587ceba1b6..274042bff1bec 100644
> > --- a/drivers/gpu/drm/xe/compat-i915-headers/intel_runtime_pm.h
> > +++ b/drivers/gpu/drm/xe/compat-i915-headers/intel_runtime_pm.h
> > @@ -20,6 +20,14 @@ static inline void enable_rpm_wakeref_asserts(void *rpm)
> >  {
> >  }
> >
> > +static inline bool
> > +intel_runtime_pm_suspended(struct xe_runtime_pm *pm)
> > +{
> > +     struct xe_device *xe = container_of(pm, struct xe_device, runtime_pm);
> > +
> > +     return pm_runtime_suspended(xe->drm.dev);
> > +}
> > +
> >  static inline intel_wakeref_t intel_runtime_pm_get(struct xe_runtime_pm *pm)
> >  {
> >       struct xe_device *xe = container_of(pm, struct xe_device, runtime_pm);
> > --
> > 2.44.2
> >
> >