Re: [Intel-gfx] [PATCH v4 1/2] drm/i915/dp: Helper for checking DDI_BUF_CTL Idle status

[Manasi Navare <manasi.d.navare@intel.com>]

On Wed, Jul 01, 2020 at 12:03:30AM +0300, Ville Syrjälä wrote:
> On Fri, Jun 26, 2020 at 04:26:40PM -0700, Manasi Navare wrote:
> > Modify the helper to add a fixed delay or poll with timeout
> > based on platform specification to check for either Idle bit
> > set (DDI_BUF_CTL is idle for disable case)
> > 
> > v3:
> > * Change the timeout to 16usecs (Ville)
> > v2:
> > * Use 2 separate functions or idle and active (Ville)
> > 
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Cc: Imre Deak <imre.deak@intel.com>
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_ddi.c | 17 ++++++++---------
> >  1 file changed, 8 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> > index 884b507c5f55..052a74625a61 100644
> > --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> > @@ -1184,16 +1184,15 @@ static void intel_prepare_hdmi_ddi_buffers(struct intel_encoder *encoder,
> >  static void intel_wait_ddi_buf_idle(struct drm_i915_private *dev_priv,
> >  				    enum port port)
> >  {
> > -	i915_reg_t reg = DDI_BUF_CTL(port);
> > -	int i;
> > -
> > -	for (i = 0; i < 16; i++) {
> > -		udelay(1);
> > -		if (intel_de_read(dev_priv, reg) & DDI_BUF_IS_IDLE)
> > -			return;
> > +	if (IS_BROXTON(dev_priv)) {
> > +		udelay(16);
> > +		return;
> >  	}
> > -	drm_err(&dev_priv->drm, "Timeout waiting for DDI BUF %c idle bit\n",
> > -		port_name(port));
> > +
> > +	if (wait_for_us((intel_de_read(dev_priv, DDI_BUF_CTL(port)) &
> > +			 DDI_BUF_IS_IDLE), 16))
> 
> 16 is the BXT number. IIRC the spec said 8 usec for the other platforms.
>

Yes I see for HSW atleast yes it says 8usecs but i left it at 16 since thats
what we always had and the only change was that BXT add a fixed delay
But if you prefer i will change it to 8us timeout?

Manasi
 
> > +		drm_err(&dev_priv->drm, "Timeout waiting for DDI BUF %c to get idle\n",
> > +			port_name(port));
> >  }
> >  
> >  static u32 hsw_pll_to_ddi_pll_sel(const struct intel_shared_dpll *pll)
> > -- 
> > 2.19.1
> 
> -- 
> Ville Syrjälä
> Intel
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