[PATCH] drm/i915/alpm: Check for alpm support before accessing alpm register

[Hogander, Jouni]

On Fri, 2025-04-25 at 20:11 +0000, Cavitt, Jonathan wrote:
> -----Original Message-----
> From: Intel-xe <intel-xe-bounces at lists.freedesktop.org> On Behalf Of
> Animesh Manna
> Sent: Friday, April 25, 2025 6:21 AM
> To: intel-gfx at lists.freedesktop.org; intel-xe at lists.freedesktop.org
> Cc: Hogander, Jouni <jouni.hogander at intel.com>; Manna, Animesh
> <animesh.manna at intel.com>
> Subject: [PATCH] drm/i915/alpm: Check for alpm support before
> accessing alpm register
> > 
> > Currently as EDP only support alpm and check for alpm support will
> > prevent DP connector to access alpm register.
> 
> I'd maybe reword this as:
> """
> Currently, only EDP supports alpm.  So, check for alpm support and
> prevent the DP connector from accessing the alpm register if doing
> so is unsupported.
> """
> I won't block on the reword, however.  As is, this patch is
> Reviewed-by: Jonathan Cavitt <jonathan.cavitt at intel.com>
> -Jonathan Cavitt

Before merging this: please consider adding "Fixes:" line.

BR,

Jouni Högander

> 
> > 
> > Signed-off-by: Animesh Manna <animesh.manna at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_alpm.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c
> > b/drivers/gpu/drm/i915/display/intel_alpm.c
> > index 482dd192d47d..1bf08b80c23f 100644
> > --- a/drivers/gpu/drm/i915/display/intel_alpm.c
> > +++ b/drivers/gpu/drm/i915/display/intel_alpm.c
> > @@ -556,7 +556,7 @@ void intel_alpm_disable(struct intel_dp
> > *intel_dp)
> >  	struct intel_display *display =
> > to_intel_display(intel_dp);
> >  	enum transcoder cpu_transcoder = intel_dp-
> > >alpm_parameters.transcoder;
> >  
> > -	if (DISPLAY_VER(display) < 20)
> > +	if (DISPLAY_VER(display) < 20 || !intel_dp->alpm_dpcd)
> >  		return;
> >  
> >  	mutex_lock(&intel_dp->alpm_parameters.lock);
> > -- 
> > 2.29.0
> > 
> >