Re: [PATCH 01/12] drm/i915: Init DRM connector polled field early

[Imre Deak <imre.deak@intel.com>]

On Fri, Jan 05, 2024 at 02:54:06PM +0200, Hogander, Jouni wrote:
> On Thu, 2024-01-04 at 10:29 +0200, Imre Deak wrote:
> > After an HPD IRQ storm on a connector intel_hpd_irq_storm_detect()
> > will
> > set the connector's HPD pin state to HPD_MARK_DISABLED and the IRQ
> > gets
> > disabled. Subsequently intel_hpd_irq_storm_switch_to_polling() will
> > enable polling for these connectors, setting the pin state to
> > HPD_DISABLED, but only if the connector's base.polled field is set to
> > DRM_CONNECTOR_POLL_HPD. intel_hpd_irq_storm_reenable_work() will
> > reenable the IRQ - after 2 minutes -  if the pin state is
> > HPD_DISABLED.
> >
> > The connectors will be created with their base.polled field set to 0,
> > which gets initialized only later in i915_hpd_poll_init_work() (using
> > intel_connector::polled). If a storm is detected on a connector after
> > it's created and IRQs are enabled on it - by intel_hpd_init() - and
> > before its bease.polled field is initialized in the above work, the
> > connector's HPD pin will stay in the HPD_MARK_DISABLED state -
> > leaving
> > the IRQ disabled indefinitely - and polling will not get enabled on
> > it as
> > intended.
> >
> > I can't see a reason for initializing base.polled in a delayed
> > manner,
> > so do this already when creating the connector, to prevent the above
> > race condition.
> 
> To me it looks like intel_connector::polled is used just to store
> original drm_connector::polled value and restore it in
> intel_hpd_irq_storm_reenable_work:
> 
>         if (connector->base.polled != connector->polled)
>                         drm_dbg(&dev_priv->drm,
>                                 "Reenabling HPD on connector %s\n",
>                                 connector->base.name);
>                 connector->base.polled = connector->polled;

Correct and restored similarly in i915_hpd_poll_init_work(). Originaly
intel_connector::polled was added to avoid misconfiguring a connector's
polled state in these two places if the two connectors share an HPD pin
(one of them needing polling the other one using the HPD pin; not sure
the exact scenario where this is actually possible). But I can't see why
at this moment we couldn't initialize the original base.polled value
early.

> From this perspective it is right thing to do to initialize  connector-
> base.polled as you are doing in this patch.
> 
> Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
> 
> >
> > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_crt.c  | 1 +
> >  drivers/gpu/drm/i915/display/intel_dp.c   | 1 +
> >  drivers/gpu/drm/i915/display/intel_dvo.c  | 1 +
> >  drivers/gpu/drm/i915/display/intel_hdmi.c | 1 +
> >  drivers/gpu/drm/i915/display/intel_sdvo.c | 2 ++
> >  drivers/gpu/drm/i915/display/intel_tv.c   | 1 +
> >  6 files changed, 7 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_crt.c
> > b/drivers/gpu/drm/i915/display/intel_crt.c
> > index abaacea5c2cc4..b330337b842a4 100644
> > --- a/drivers/gpu/drm/i915/display/intel_crt.c
> > +++ b/drivers/gpu/drm/i915/display/intel_crt.c
> > @@ -1069,6 +1069,7 @@ void intel_crt_init(struct drm_i915_private
> > *dev_priv)
> >         } else {
> >                 intel_connector->polled = DRM_CONNECTOR_POLL_CONNECT;
> >         }
> > +       intel_connector->base.polled = intel_connector->polled;
> >
> >         if (HAS_DDI(dev_priv)) {
> >                 assert_port_valid(dev_priv, PORT_E);
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> > b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 9ff0cbd9c0df5..fed649af8fc85 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -6469,6 +6469,7 @@ intel_dp_init_connector(struct
> > intel_digital_port *dig_port,
> >                 connector->interlace_allowed = true;
> >
> >         intel_connector->polled = DRM_CONNECTOR_POLL_HPD;
> > +       intel_connector->base.polled = intel_connector->polled;
> >
> >         intel_connector_attach_encoder(intel_connector,
> > intel_encoder);
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dvo.c
> > b/drivers/gpu/drm/i915/display/intel_dvo.c
> > index 9111e9d46486d..83898ba493d16 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dvo.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dvo.c
> > @@ -536,6 +536,7 @@ void intel_dvo_init(struct drm_i915_private
> > *i915)
> >         if (intel_dvo->dev.type == INTEL_DVO_CHIP_TMDS)
> >                 connector->polled = DRM_CONNECTOR_POLL_CONNECT |
> >                         DRM_CONNECTOR_POLL_DISCONNECT;
> > +       connector->base.polled = connector->polled;
> >
> >         drm_connector_init_with_ddc(&i915->drm, &connector->base,
> >                                     &intel_dvo_connector_funcs,
> > diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c
> > b/drivers/gpu/drm/i915/display/intel_hdmi.c
> > index eedef8121ff7c..55048c56bc527 100644
> > --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> > @@ -3017,6 +3017,7 @@ void intel_hdmi_init_connector(struct
> > intel_digital_port *dig_port,
> >                 connector->ycbcr_420_allowed = true;
> >
> >         intel_connector->polled = DRM_CONNECTOR_POLL_HPD;
> > +       intel_connector->base.polled = intel_connector->polled;
> >
> >         if (HAS_DDI(dev_priv))
> >                 intel_connector->get_hw_state =
> > intel_ddi_connector_get_hw_state;
> > diff --git a/drivers/gpu/drm/i915/display/intel_sdvo.c
> > b/drivers/gpu/drm/i915/display/intel_sdvo.c
> > index 9218047495fb4..4e4a87f841787 100644
> > --- a/drivers/gpu/drm/i915/display/intel_sdvo.c
> > +++ b/drivers/gpu/drm/i915/display/intel_sdvo.c
> > @@ -2805,6 +2805,7 @@ intel_sdvo_dvi_init(struct intel_sdvo
> > *intel_sdvo, u16 type)
> >         } else {
> >                 intel_connector->polled = DRM_CONNECTOR_POLL_CONNECT
> > | DRM_CONNECTOR_POLL_DISCONNECT;
> >         }
> > +       intel_connector->base.polled = intel_connector->polled;
> >         encoder->encoder_type = DRM_MODE_ENCODER_TMDS;
> >         connector->connector_type = DRM_MODE_CONNECTOR_DVID;
> >
> > @@ -2880,6 +2881,7 @@ intel_sdvo_analog_init(struct intel_sdvo
> > *intel_sdvo, u16 type)
> >         intel_connector = &intel_sdvo_connector->base;
> >         connector = &intel_connector->base;
> >         intel_connector->polled = DRM_CONNECTOR_POLL_CONNECT;
> > +       intel_connector->base.polled = intel_connector->polled;
> >         encoder->encoder_type = DRM_MODE_ENCODER_DAC;
> >         connector->connector_type = DRM_MODE_CONNECTOR_VGA;
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_tv.c
> > b/drivers/gpu/drm/i915/display/intel_tv.c
> > index d4386cb3569e0..f3598fe39fda5 100644
> > --- a/drivers/gpu/drm/i915/display/intel_tv.c
> > +++ b/drivers/gpu/drm/i915/display/intel_tv.c
> > @@ -1990,6 +1990,7 @@ intel_tv_init(struct drm_i915_private
> > *dev_priv)
> >          * More recent chipsets favour HDMI rather than integrated S-
> > Video.
> >          */
> >         intel_connector->polled = DRM_CONNECTOR_POLL_CONNECT;
> > +       intel_connector->base.polled = intel_connector->polled;
> >
> >         drm_connector_init(&dev_priv->drm, connector,
> > &intel_tv_connector_funcs,
> >                            DRM_MODE_CONNECTOR_SVIDEO);
>