Re: [PATCH 05/23] drm/xe/xe3p_lpm: Stop reading the CTC_MODE register

[Matt Roper <matthew.d.roper@intel.com>]

On Tue, Oct 14, 2025 at 09:40:50AM -0700, Matt Roper wrote:
> On Mon, Oct 13, 2025 at 08:24:37PM -0700, Lucas De Marchi wrote:
> > From: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
> > 
> > CTC_MODE register is removed by Xe3p.  Stop reading that register on
> > Xe3p and later platforms.
> > 
> > Bspec: 62395
> > Signed-off-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
> > Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
> 
> Reviewed-by: Matt Roper <matthew.d.roper@intel.com>

Actually, based on Shekhar's comment I took a 2nd look and maybe this is
a case where it should be a GRAPHICS_VER check instead of GT_VER.  See
my reply to Shekhar for details.


Matt

> 
> > ---
> >  drivers/gpu/drm/xe/xe_gt_clock.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_gt_clock.c b/drivers/gpu/drm/xe/xe_gt_clock.c
> > index 4f011d1573c65..26052710be8a7 100644
> > --- a/drivers/gpu/drm/xe/xe_gt_clock.c
> > +++ b/drivers/gpu/drm/xe/xe_gt_clock.c
> > @@ -57,6 +57,10 @@ static void read_crystal_clock(struct xe_gt *gt, u32 rpm_config_reg, u32 *freq,
> >  
> >  static void check_ctc_mode(struct xe_gt *gt)
> >  {
> > +	/* CTC_MODE register is removed by Xe3p */
> > +	if (GT_VER(gt) >= 35)
> > +		return;
> > +
> >  	/*
> >  	 * CTC_MODE[0] = 1 is definitely not supported for Xe2 and later
> >  	 * platforms.  In theory it could be a valid setting for pre-Xe2
> > 
> > -- 
> > 2.51.0
> > 
> 
> -- 
> Matt Roper
> Graphics Software Engineer
> Linux GPU Platform Enablement
> Intel Corporation

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation