Re: [PATCH] drm/i915: Don't try to use negative pll_id.

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Nov 01, 2017 at 12:13:42PM -0700, Rodrigo Vivi wrote:
> On Wed, Nov 01, 2017 at 06:56:55PM +0000, Ville Syrjälä wrote:
> > On Wed, Nov 01, 2017 at 11:44:58AM -0700, Rodrigo Vivi wrote:
> > > It is unlikely we are getting the -1 here.
> > > But if we propagate that pll_id -1 to the rest of the code
> > > we might have funny calculations on link_clock and who
> > > knows what registers we end up accessing.
> > > 
> > > Better to protect the code.
> > > 
> > > Also better with errno number instead of generic -1.
> > > 
> > > Cc: Manasi Navare <manasi.d.navare@intel.com>
> > > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_ddi.c      | 10 ++++++++++
> > >  drivers/gpu/drm/i915/intel_dpll_mgr.c |  2 +-
> > >  2 files changed, 11 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> > > index ace674cd79b9..2c6abdbf33ea 100644
> > > --- a/drivers/gpu/drm/i915/intel_ddi.c
> > > +++ b/drivers/gpu/drm/i915/intel_ddi.c
> > > @@ -1283,6 +1283,11 @@ static void cnl_ddi_clock_get(struct intel_encoder *encoder,
> > >  
> > >  	pll_id = intel_get_shared_dpll_id(dev_priv, pipe_config->shared_dpll);
> > >  
> > > +	if (pll_id < 0) {
> > > +		DRM_ERROR("PLL not found\n");
> > > +		return;
> > > +	}
> > > +
> > >  	cfgcr0 = I915_READ(CNL_DPLL_CFGCR0(pll_id));
> > 
> > Don't we have the dpll state already read out?
> > 
> > crtc_state->dll_hw_state.cfgcr0 etc.?
> 
> oh! we do!
> Also during calc_wrpll_link we should be using this,
> shouldn't we?!
> 
> Probably my bad when doing this code looking to skl code...
> 
> Same thing on skl case, right?!

On all platforms I'd say. This is all probably just leftovers from before
we had the dpll manager.

I suspect we should just move all these foo_calc_wrpll_link() etc.
functions into the dpll manager. Not sure if we could just directly
fill out the port_clock in the dpll manager actually. Hmm. I guess not
in the .get_hw_state() at least since we don't pass the full crtc state
there. But we could perhaps have some kind of .clock_get() function
that'd be similar to the i9xx/vlv/chv_clock_get(), except we'd just call
it from the DDI code where we currently call these hand rolled
functions.

> > 
> > >  
> > >  	if (cfgcr0 & DPLL_CFGCR0_HDMI_MODE) {
> > > @@ -1337,6 +1342,11 @@ static void skl_ddi_clock_get(struct intel_encoder *encoder,
> > >  
> > >  	pll_id = intel_get_shared_dpll_id(dev_priv, pipe_config->shared_dpll);
> > >  
> > > +	if (pll_id < 0) {
> > > +		DRM_ERROR("PLL not found\n");
> > > +		return;
> > > +	}
> > > +
> > >  	dpll_ctl1 = I915_READ(DPLL_CTRL1);
> > >  
> > >  	if (dpll_ctl1 & DPLL_CTRL1_HDMI_MODE(pll_id)) {
> > > diff --git a/drivers/gpu/drm/i915/intel_dpll_mgr.c b/drivers/gpu/drm/i915/intel_dpll_mgr.c
> > > index a83bf1c38e05..c4a7f39e173a 100644
> > > --- a/drivers/gpu/drm/i915/intel_dpll_mgr.c
> > > +++ b/drivers/gpu/drm/i915/intel_dpll_mgr.c
> > > @@ -102,7 +102,7 @@ intel_get_shared_dpll_id(struct drm_i915_private *dev_priv,
> > >  {
> > >  	if (WARN_ON(pll < dev_priv->shared_dplls||
> > >  		    pll > &dev_priv->shared_dplls[dev_priv->num_shared_dpll]))
> > > -		return -1;
> > > +		return -ENOENT;
> > >  
> > >  	return (enum intel_dpll_id) (pll - dev_priv->shared_dplls);
> > >  }
> > > -- 
> > > 2.13.6
> > > 
> > > _______________________________________________
> > > Intel-gfx mailing list
> > > Intel-gfx@lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> > 
> > -- 
> > Ville Syrjälä
> > Intel OTC

-- 
Ville Syrjälä
Intel OTC
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