[Intel-gfx] [PATCH] drm/i915/dp: DP PHY compliance for JSL

Fri Jun 12 19:38:59 UTC 2020

On Fri, Jun 12, 2020 at 10:21:31PM +0300, Ville Syrjälä wrote:
> On Fri, Jun 12, 2020 at 12:12:25PM -0700, Manasi Navare wrote:
> > On Fri, Jun 12, 2020 at 10:01:19PM +0300, Ville Syrjälä wrote:
> > > On Fri, Jun 12, 2020 at 11:44:13AM -0700, Manasi Navare wrote:
> > > > On Fri, Jun 12, 2020 at 09:36:37PM +0300, Ville Syrjälä wrote:
> > > > > On Fri, Jun 12, 2020 at 11:25:42AM -0700, Manasi Navare wrote:
> > > > > > On Fri, Jun 05, 2020 at 12:03:19AM +0300, Ville Syrjälä wrote:
> > > > > > > On Thu, Jun 04, 2020 at 08:01:03PM +0000, Almahallawy, Khaled wrote:
> > > > > > > > On Thu, 2020-06-04 at 22:06 +0300, Ville Syrjälä wrote:
> > > > > > > > > On Thu, Jun 04, 2020 at 10:33:48AM +0530, Vidya Srinivas wrote:
> > > > > > > > > > Signed-off-by: Khaled Almahallawy <khaled.almahallawy at intel.com>
> > > > > > > > > > Signed-off-by: Vidya Srinivas <vidya.srinivas at intel.com>
> > > > > > > > > > ---
> > > > > > > > > >  drivers/gpu/drm/i915/display/intel_dp.c | 40
> > > > > > > > > > ++++++++++++++++++++++++++-------
> > > > > > > > > >  1 file changed, 32 insertions(+), 8 deletions(-)
> > > > > > > > > > 
> > > > > > > > > > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> > > > > > > > > > b/drivers/gpu/drm/i915/display/intel_dp.c
> > > > > > > > > > index 7223367171d1..44663e8ac9a1 100644
> > > > > > > > > > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > > > > > > > > > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > > > > > > > > > @@ -5470,22 +5470,32 @@ intel_dp_autotest_phy_ddi_disable(struct
> > > > > > > > > > intel_dp *intel_dp)
> > > > > > > > > >  	struct drm_i915_private *dev_priv = to_i915(dev);
> > > > > > > > > >  	struct intel_crtc *crtc = to_intel_crtc(intel_dig_port-
> > > > > > > > > > >base.base.crtc);
> > > > > > > > > >  	enum pipe pipe = crtc->pipe;
> > > > > > > > > > -	u32 trans_ddi_func_ctl_value, trans_conf_value,
> > > > > > > > > > dp_tp_ctl_value;
> > > > > > > > > > +	u32 trans_ddi_func_ctl_value, trans_conf_value,
> > > > > > > > > > dp_tp_ctl_value, trans_ddi_port_mask;
> > > > > > > > > > +	enum port port = intel_dig_port->base.port;
> > > > > > > > > > +	i915_reg_t dp_tp_reg;
> > > > > > > > > > +
> > > > > > > > > > +	if (IS_ELKHARTLAKE(dev_priv)) {
> > > > > > > > > > +		dp_tp_reg = DP_TP_CTL(port);
> > > > > > > > > > +		trans_ddi_port_mask = TRANS_DDI_PORT_MASK;
> > > > > > > > > > +	} else if (IS_TIGERLAKE(dev_priv)) {
> > > > > > > > > > +		dp_tp_reg = TGL_DP_TP_CTL(pipe);
> > > > > > > > > > +		trans_ddi_port_mask = TGL_TRANS_DDI_PORT_MASK;
> > > > > > > > > > +	}
> > > > > > > > > >  
> > > > > > > > > >  	trans_ddi_func_ctl_value = intel_de_read(dev_priv,
> > > > > > > > > >  						 TRANS_DDI_FUNC_CTL(pip
> > > > > > > > > > e));
> > > > > > > > > >  	trans_conf_value = intel_de_read(dev_priv, PIPECONF(pipe));
> > > > > > > > > > -	dp_tp_ctl_value = intel_de_read(dev_priv, TGL_DP_TP_CTL(pipe));
> > > > > > > > > >  
> > > > > > > > > > +	dp_tp_ctl_value = intel_de_read(dev_priv, dp_tp_reg);
> > > > > > > > > >  	trans_ddi_func_ctl_value &= ~(TRANS_DDI_FUNC_ENABLE |
> > > > > > > > > > -				      TGL_TRANS_DDI_PORT_MASK);
> > > > > > > > > > +					trans_ddi_port_mask);
> > > > > > > > > >  	trans_conf_value &= ~PIPECONF_ENABLE;
> > > > > > > > > >  	dp_tp_ctl_value &= ~DP_TP_CTL_ENABLE;
> > > > > > > > > >  
> > > > > > > > > >  	intel_de_write(dev_priv, PIPECONF(pipe), trans_conf_value);
> > > > > > > > > >  	intel_de_write(dev_priv, TRANS_DDI_FUNC_CTL(pipe),
> > > > > > > > > >  		       trans_ddi_func_ctl_value);
> > > > > > > > > > -	intel_de_write(dev_priv, TGL_DP_TP_CTL(pipe), dp_tp_ctl_value);
> > > > > > > > > > +	intel_de_write(dev_priv, dp_tp_reg, dp_tp_ctl_value);
> > > > > > > > > 
> > > > > > > > > All this ad-hoc modeset code really should not exist. It's going to
> > > > > > > > > have different bugs than the norma modeset paths, so compliance
> > > > > > > > > testing
> > > > > > > > > this special code proves absolutely nothing about the normal modeset
> > > > > > > > > code. IMO someone needs to take up the task of rewrtiting all this to
> > > > > > > > > just perform normal modesets.
> > > > > > > > 
> > > > > > > > Agree. I've just found that we get kernel NULL pointer dereference and
> > > > > > > > panic when we try to access to_intel_crtc(intel_dig_port-
> > > > > > > > >base.base.crtc).
> > > > > > > 
> > > > > > > Yeah, that's a legacy pointer which should no longer be used at all
> > > > > > > with atomic drivers. I'm slowly trying to clear out all this legacy
> > > > > > > cruft. The next step I had hoped to take was
> > > > > > > https://patchwork.freedesktop.org/series/76993/ but then this
> > > > > > > compliacnce stuff landed and threw another wrench into the works.
> > > > > > 
> > > > > > We had several discussions on design of DP PHY compliance and the patches were on the M-L
> > > > > > for quite some time without anyone giving feedback on the actual design of whether they should
> > > > > > happen through modeset or directly from the PHY comp request short pulse.
> > > > > > My first feedback was also that this should happen through a complete modeset where after we get
> > > > > > PHY comp request we send a uevent like we do for link layer compliance and then trigger a full modeset.
> > > > > > But honestly that was just a lot of overhead and 
> > > > > > The reason we decided to go with this ad hoc approach was that with PHY compliance request,
> > > > > > nothing really changes in terms of link parameters so we do not need to go through
> > > > > > a complete modeset request unlike link layer compliance where we need to do compute config
> > > > > > all over again to do the link params computation.
> > > > > > 
> > > > > > Every PHY comp request first sends a link layer comp request that does a full modeset
> > > > > > and sets up the desired link rate/lane count.
> > > > > > Then with PHY request, all we need to do is disable pipe conf, dp_tp_ctl, set the PHY patterns
> > > > > > and renable the pipe conf and dp_tp_ctl without interfering and doing anything with a full modeset.
> > > > > > 
> > > > > > Now i think if we need to scale this to other platforms, can we add a per platform hook
> > > > > > for handle_phy_request that gets the correct DP_TP_CTL etc and sets up the PHY patterns and
> > > > > > reenables the already set link?
> > > > > > 
> > > > > > We have thoroughly tested this using the scopes and DPR 100 and it has been working correctly
> > > > > > with the existing IGT compliance tool so IMO no need to rewrite the entire set of patches.
> > > > > > 
> > > > > > Ville, Khaled ?
> > > > > 
> > > > > You're just multiplying the amount of work and bugs we have
> > > > > for every platform.
> > > > > 
> > > > > And as said testing some special compliance paths proves
> > > > > pretty much nothing about the real code paths. So the only
> > > > > point of that code AFAICS it to tick some "we haz
> > > > > compliance code?" checkbox in some random spreadsheet instead
> > > > > of actually providing evidence that our real code works
> > > > > correctly.
> > > > >
> > > > 
> > > > I thougt the whole point of PHY compliance is not to be able to see if the
> > > > driver can do a modeset but just to confirm that driver is able to send
> > > > the requested patterns out on already enabled link. So shouldnt doing this
> > > > directly through the phy request handling on short pulse suffice?
> > > 
> > > You're not proving the driver proper can transmit the requested stuff,
> > > you're only proving the special compliance code can do that. I could
> > > easily break the normal codepaths and yet this magic compliance thing
> > > could still indicate that everything is hunky dory.
> > >
> >  
> > > > 
> > > > But if we want to insert this in the modeset what should be the flow:
> > > > - AFter getting PHY request, store the requested PHY patterns, send a uevent
> > > 
> > > You don't really need any uevent. We coukd do the stuff directly from 
> > > the hotplug work.
> > > 
> > > > - This will trigger a complete modeset, in this path for atomic check, see
> > > > if PHY compliance test active then ignore recomputing the parameters and
> > > > also in the commit tail, only disable the Pipeconf, dp_tp_ctl and send these patterns
> > > > and then reenable?
> > > 
> > > We should just do a full modeset if possible. Randomly turning the
> > > pipe/etc. on/off without following the proper modeset sequence is
> > > dubious at best.
> > 
> > how do we trigger a full modeset directly from the hotplug work just from
> > within the kernel? We faced the same problem with link layer compliance
> > and hence we decided to send the uevent there to trigger a ful modeset.
> 
> The full modeset via userspace route is only needed if the resolution
> needs to be changed since that's something userspace gets to decide.
> If the current mode is still OK we can directly trigger the modeset
> from the kernel. Not sure if we do or not.
> 
> We do a full modeset for HDMI when the sink forgets that scrambling
> was supposed to be on, and I'm a bit tempted to do the same for
> plain old DP retraining to get rid of the special case code for
> that (and to actually follow the modeset seqeunce properly when
> doing retraining).
>

For retraining we dont have any special case code right, we just fallback and then send uevent.
Oh but do you mean like getting rid of setting the link status and forcing a full modeset etc?

So for PHY compliance, we do something similar to calling modeset_pipe() from
intel_hdmi_reset_link()? So call this modeset_pipe from  intel_dp_autotest_phy_pattern() after
storing the requested phy patterns in a compliance struct?

Manasi

> -- 
> Ville Syrjälä
> Intel