[Intel-gfx] [PATCH v2 3/4] drm/i915/psr: Control PSR interrupts via debugfs

[Pandiyan, Dhinakaran]

On Tue, 2018-03-27 at 11:26 +0100, Chris Wilson wrote:
> Quoting Dhinakaran Pandiyan (2018-03-27 02:16:22)
> > Interrupts other than the one for AUX errors are required only for debug,
> > so unmask them via debugfs when the user requests debug.
> > 
> > User can make such a request with
> > echo 1 > <DEBUG_FS>/dri/0/i915_edp_psr_debug
> > 
> > v2: Unroll loops (Ville)
> >     Avoid resetting error mask bits.
> > 
> > Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > Cc: Chris Wilson <chris at chris-wilson.co.uk>
> > Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_debugfs.c | 36 +++++++++++++++++++++++-
> >  drivers/gpu/drm/i915/i915_drv.h     |  1 +
> >  drivers/gpu/drm/i915/i915_irq.c     | 55 +++++++++++--------------------------
> >  drivers/gpu/drm/i915/intel_drv.h    |  2 ++
> >  drivers/gpu/drm/i915/intel_psr.c    | 54 ++++++++++++++++++++++++++++++++++++
> >  5 files changed, 108 insertions(+), 40 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> > index 7816cd53100a..6fd801ef7cbb 100644
> > --- a/drivers/gpu/drm/i915/i915_debugfs.c
> > +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> > @@ -2690,6 +2690,39 @@ static int i915_edp_psr_status(struct seq_file *m, void *data)
> >         return 0;
> >  }
> >  
> > +static int
> > +i915_edp_psr_debug_set(void *data, u64 val)
> > +{
> > +       struct drm_i915_private *dev_priv = data;
> > +
> > +       if (!CAN_PSR(dev_priv))
> > +               return -ENODEV;
> > +
> > +       if (val < 0  || val > 1)
> > +               return -EINVAL;
> > +
> > +       DRM_DEBUG_KMS("%s PSR debug\n", val == 1 ? "Enabling" : "Disabling");
> > +       intel_psr_debug_control(dev_priv, val);
> > +
> > +       return 0;
> > +}
> 
> A really useful trick for features like this (that we think should be
> used wherever it can) is just to enable debug while the debugfs file is
> open. igt need only do something like
> 	openat(debugfs_dir, "i915_edp_psr_debug", O_RDONLY);

That is neat.

We also want to support user enabling/disabling PSR debug via shell. The
semantics get slightly confusing taking that into consideration.

For example,
1) should cat $debugfs/i915_edp_psr_debug 
also enable debug or just print the current status of debug
2) if the file is already open (debug enabled), should
echo 0 > $debugfs/i915_edp_psr_debug disable debug or check for the
refcount to drop to zero.

Choosing the correct solution and implementing it correctly feels like
we'd be over-engineering.


> and then it will be automatically released and the system returned to
> default when terminated. You can then enforce exclusive access or keep an
> open count.
> -Chris
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