Re: [PATCH v4 2/2] drm/i915/dp: Extend BDW DP audio workaround to GEN9 platforms

[Jani Nikula <jani.nikula@intel.com>]

On Tue, 01 Nov 2016, "Pandiyan, Dhinakaran" <dhinakaran.pandiyan@intel.com> wrote:
> On Tue, 2016-11-01 at 21:35 +0200, Jani Nikula wrote:
>> On Tue, 01 Nov 2016, Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com> wrote:
>> > According to BSpec, cdclk for BDW has to be not less than 432 MHz with DP
>> > audio enabled, port width x4, and link rate HBR2 (5.4 GHz). With cdclk less
>> > than 432 MHz, enabling audio leads to pipe FIFO underruns and displays
>> > cycling on/off.
>> >
>> > Let's apply this work around to GEN9 platforms too, as it fixes the same
>> > issue.
>> 
>> I'm too tired to read bspec now, but is gen9 really the answer, or just
>> Skylake?
>> 
>> 
>
> Gen9, applies to BXT and KBL as well.

I'll take your word for it, and with that,

Reviewed-by: Jani Nikula <jani.nikula@intel.com>



>
> -DK
>
>> >
>> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97907
>> > Cc: stable@vger.kernel.org
>> > Cc: Libin Yang <libin.yang@linux.intel.com>
>> > Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
>> > ---
>> >  drivers/gpu/drm/i915/intel_display.c | 6 ++++--
>> >  1 file changed, 4 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
>> > index 37483ee..c0ae147 100644
>> > --- a/drivers/gpu/drm/i915/intel_display.c
>> > +++ b/drivers/gpu/drm/i915/intel_display.c
>> > @@ -10264,8 +10264,10 @@ static void bxt_modeset_commit_cdclk(struct drm_atomic_state *old_state)
>> >  static int bdw_adjust_min_pipe_pixel_rate(struct intel_crtc_state *crtc_state,
>> >  					  int pixel_rate)
>> >  {
>> > +	struct drm_device *dev = crtc_state->base.crtc->dev;
>> 
>> Nitpick, I guess I'd make that
>> 
>> 	struct drm_i915_private *dev_priv = to_i915(crtc_state->base.crtc->dev);
>> 
>> but no big deal.
>> 
>> > +
>> >  	/* pixel rate mustn't exceed 95% of cdclk with IPS on BDW */
>> > -	if (crtc_state->ips_enabled)
>> > +	if (IS_BROADWELL(to_i915(dev)) && crtc_state->ips_enabled)
>> >  		pixel_rate = DIV_ROUND_UP(pixel_rate * 100, 95);
>> >  
>> >  	/* BSpec says "Do not use DisplayPort with CDCLK less than
>> > @@ -10307,7 +10309,7 @@ static int ilk_max_pixel_rate(struct drm_atomic_state *state)
>> >  
>> >  		pixel_rate = ilk_pipe_pixel_rate(crtc_state);
>> >  
>> > -		if (IS_BROADWELL(dev_priv))
>> > +		if (IS_BROADWELL(dev_priv) || IS_GEN9(dev_priv))
>> >  			pixel_rate = bdw_adjust_min_pipe_pixel_rate(crtc_state,
>> >  								    pixel_rate);
>> 
>

-- 
Jani Nikula, Intel Open Source Technology Center