[Intel-gfx] [PATCH 03/16] drm/i915/bxt: Add a note about BXT_PORT_CL1CM_DW30 being read-only

[Imre Deak]

On pe, 2016-04-08 at 21:12 +0300, Imre Deak wrote:
> On pe, 2016-04-08 at 21:02 +0300, Ville Syrjälä wrote:
> > On Fri, Apr 01, 2016 at 04:02:34PM +0300, Imre Deak wrote:
> > > This register is read-only, so we have never actually set
> > > OCL2_LDOFUSE_PWR_DIS in it as specified by the specification. Add
> > > a
> > > code
> > > comment about this. I filed a specification update request to
> > > clarify
> > > this there.
> > 
> > Hmm. Interesting. It's r/w on my CHV, and the PHY spec agrees. Of
> > course
> > I can't really tell whether it has any effect on the x1 PHY. If I
> > set
> > it
> > on the x2 PHY it definitely makes the channel unusable.
> 
> Note that meanwhile the corresponding BSpec change request got
> updated
> to "Confirmed"/"Won't be fixed".

Sorry, it's just "Confirmed".

> > > CC: Arthur J Runyan <arthur.j.runyan at intel.com>
> > > Signed-off-by: Imre Deak <imre.deak at intel.com>
> > > 
> > > ---
> > > 
> > > [ Art, CC'ing you in case you know if this would have an effect
> > > on
> > >   anything. ]
> > > ---
> > >  drivers/gpu/drm/i915/intel_ddi.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_ddi.c
> > > b/drivers/gpu/drm/i915/intel_ddi.c
> > > index 2758622..f91306e 100644
> > > --- a/drivers/gpu/drm/i915/intel_ddi.c
> > > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> > > @@ -1798,6 +1798,9 @@ static void broxton_phy_init(struct
> > > drm_i915_private *dev_priv,
> > >  	 * enabled.
> > >  	 * TODO: port C is only connected on BXT-P, so on BXT0/1
> > > we should
> > >  	 * power down the second channel on PHY0 as well.
> > > +	 *
> > > +	 * FIXME: Clarify programming of the following, the
> > > register is
> > > +	 * read-only with bit 6 fixed at 0 at least in stepping
> > > A.
> > >  	 */
> > >  	if (phy == DPIO_PHY1)
> > >  		val |= OCL2_LDOFUSE_PWR_DIS;