> -----Original Message----- > From: Roper, Matthew D <matthew.d.roper@xxxxxxxxx> > Sent: Monday, September 23, 2024 11:39 PM > To: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > Cc: Kandpal, Suraj <suraj.kandpal@xxxxxxxxx>; intel-gfx@xxxxxxxxxxxxxxxxxxxxx; > Shankar, Uma <uma.shankar@xxxxxxxxx> > Subject: Re: [PATCH 1/2] drm/i915/hotplug: Reduce SHPD_FLITER_CNT for > DISPLAY_VER() == 12 > > On Mon, Sep 23, 2024 at 08:38:35PM +0300, Ville Syrjälä wrote: > > On Mon, Sep 23, 2024 at 08:40:07AM +0530, Suraj Kandpal wrote: > > > Reduce SHPD_CNT to 250us for display version 12 as it lines up with > > > DP1.4a(Table3-4) spec. > > > > > > --v2 > > > -Update commit message and comment [Matt] > > > > > > Signed-off-by: Suraj Kandpal <suraj.kandpal@xxxxxxxxx> > > > --- > > > drivers/gpu/drm/i915/display/intel_hotplug_irq.c | 6 +++++- > > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/gpu/drm/i915/display/intel_hotplug_irq.c > > > b/drivers/gpu/drm/i915/display/intel_hotplug_irq.c > > > index 2c4e946d5575..8427386132e6 100644 > > > --- a/drivers/gpu/drm/i915/display/intel_hotplug_irq.c > > > +++ b/drivers/gpu/drm/i915/display/intel_hotplug_irq.c > > > @@ -849,7 +849,11 @@ static void icp_hpd_irq_setup(struct > drm_i915_private *dev_priv) > > > enabled_irqs = intel_hpd_enabled_irqs(dev_priv, dev_priv- > >display.hotplug.pch_hpd); > > > hotplug_irqs = intel_hpd_hotplug_irqs(dev_priv, > > > dev_priv->display.hotplug.pch_hpd); > > > > > > - if (INTEL_PCH_TYPE(dev_priv) <= PCH_TGP) > > > + /* > > > + * We reduce the value to 250us to be able to detect SHPD when an > external display > > > + * is connected. This is also expected of us as stated in DP1.4a Table 3-4. > > > + */ > > > + if (INTEL_PCH_TYPE(dev_priv) < PCH_TGP) > > > intel_uncore_write(&dev_priv->uncore, SHPD_FILTER_CNT, > SHPD_FILTER_CNT_500_ADJ); > > > else > > > intel_uncore_write(&dev_priv->uncore, SHPD_FILTER_CNT, > > > SHPD_FILTER_CNT_250); > > > > IMO if we start reducing this for older platforms then we should just > > do it for all of them, instead of based on some random cutoff. > > There is a note in the bspec (page 4342) that says > > "Program SHPD_FILTER_CNT with the "500 microseconds adjusted" > value before enabling hotplug detection." > > for CNP and ICP which is where the cutoff originally came from. I'm not sure > about CML (which uses CNP), but ICL at least supports DP1.4a, so I think the > note in the bspec is probably just outdated and we'd still want 250 to ensure we > align with the DP spec. > > So I'd suggest just dropping the condition in this function and using 250us here. > We can probably leave things be in spt_hpd_irq_setup which gets used for > CML/CNP. > Sure will do that Regards, Suraj Kandpal > > Matt > > > > > -- > > Ville Syrjälä > > Intel > > -- > Matt Roper > Graphics Software Engineer > Linux GPU Platform Enablement > Intel Corporation
