RE: [PATCH] drm/i915/display: C20 clock state verification

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

On Fri, 15 Dec 2023, "Kahola, Mika" <mika.kahola@intel.com> wrote:
>> -----Original Message-----
>> From: Deak, Imre <imre.deak@intel.com>
>> Sent: Friday, December 15, 2023 11:02 AM
>> To: Kahola, Mika <mika.kahola@intel.com>; intel-gfx@lists.freedesktop.org
>> Subject: Re: [PATCH] drm/i915/display: C20 clock state verification
>> 
>> On Fri, Dec 15, 2023 at 10:53:36AM +0200, Imre Deak wrote:
>> > On Fri, Dec 15, 2023 at 10:00:57AM +0200, Mika Kahola wrote:
>> > > Add clock state verification for C20. Since we are usign either A or
>> > > B contexts, which are selected based on clock rate, we first need to
>> > > calculate hw clock and use that clock to select which context we are
>> > > using.
>> >
>> > Could the description be clearer that the patch _fixes_ the context
>> > selection? (Also the subject line should always say _what_ the patch
>> > does.)
> OK, should I add the fixes tag as well? I will reword the commit message to better describe what's going on in this patch.
>
>> >
>> > >
>> > > Signed-off-by: Mika Kahola <mika.kahola@intel.com>
>> > > ---
>> > >  drivers/gpu/drm/i915/display/intel_cx0_phy.c | 8 +++++++-
>> > >  1 file changed, 7 insertions(+), 1 deletion(-)
>> > >
>> > > diff --git a/drivers/gpu/drm/i915/display/intel_cx0_phy.c
>> > > b/drivers/gpu/drm/i915/display/intel_cx0_phy.c
>> > > index 775c1c4a8978..6757e9f941e4 100644
>> > > --- a/drivers/gpu/drm/i915/display/intel_cx0_phy.c
>> > > +++ b/drivers/gpu/drm/i915/display/intel_cx0_phy.c
>> > > @@ -3079,8 +3079,9 @@ static void intel_c20pll_state_verify(const struct intel_crtc_state *state,
>> > >  	const struct intel_c20pll_state *mpll_sw_state = &state->cx0pll_state.c20;
>> > >  	bool use_mplla;
>> > >  	int i;
>> > > +	int hw_clock = intel_c20pll_calc_port_clock(encoder,
>> > > +mpll_hw_state);
>> > >
>> > > -	use_mplla = intel_c20_use_mplla(mpll_hw_state->clock);
>> > > +	use_mplla = intel_c20_use_mplla(hw_clock);
>> >
>> > It's mpll_hw_state->tx[0] C20_PHY_USE_MPLLB which tells the HW which
>> > context to use, so I think it's better to use the same condition here.
>
> Maybe I will ditch the use_mplla completely and go directly with
>
> if (mpll_hw_state->tx]0] & C20_PHY_USE_MPLLB) { .. }
>
> instead?

You should first verify that the hw and sw states for use_mplla agree.

If they don't, it doesn't matter which one you use.

BR,
Jani.


>
>> 
>> You could also add a check intel_c20_use_mplla(clock) matches the above flag.
>> 
>> >
>> > >  	if (use_mplla) {
>> > >  		for (i = 0; i < ARRAY_SIZE(mpll_sw_state->mplla); i++) {
>> > >  			I915_STATE_WARN(i915, mpll_hw_state->mplla[i] !=
>> > > mpll_sw_state->mplla[i], @@ -3110,6 +3111,11 @@ static void intel_c20pll_state_verify(const struct intel_crtc_state *state,
>> > >  				crtc->base.base.id, crtc->base.name, i,
>> > >  				mpll_sw_state->cmn[i], mpll_hw_state->cmn[i]);
>> > >  	}
>> > > +
>> > > +	I915_STATE_WARN(i915, hw_clock != mpll_sw_state->clock,
>> > > +			"[CRTC:%d:%s] mismatch in C20: Register CLOCK (expected %d, found %d)",
>> > > +			crtc->base.base.id, crtc->base.name,
>> > > +			mpll_sw_state->clock, hw_clock);
>> >
>> > I think the intel_crtc_state::port_clock SW/HW state verification is
>> > equivalent to the above, but it's good to verify it here as well. I
>> > would store hw_clock to mpll_hw_state->clock in
>> > intel_c20pll_readout_hw_state() though.
> Well, clock is part of pll structure anyway, so it might as well be checked here too.
>
> I will store hw clock too in intel_c20pll_readout_hw_state()
>
> Thanks!
> Mika  
>
>> >
>> > >  }
>> > >
>> > >  void intel_cx0pll_state_verify(struct intel_atomic_state *state,
>> > > --
>> > > 2.34.1
>> > >

-- 
Jani Nikula, Intel