On Thu, Jun 14, 2018 at 03:42:42PM +0300, Jani Nikula wrote:
> On Wed, 13 Jun 2018, Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx> wrote:
> > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> >
> > While Bspec doesn't list a specific sequence for turning off the DP port
> > on g4x we are getting an underrun if the port is disabled in the
> > .disable() hook. Looks like the pipe stops when the port stops, and by
> > that time the plane disable may not have completed yet. Also the plane(s)
> > seem to end up in some wonky state when this happens as they also signal
> > another underrun immediately after we turn them back on during the next
> > enable sequence.
> >
> > We could add a vblank wait in .disable() to avoid wedging the planes,
> > but I assume we're still tripping up the pipe in some way. So it seems
> > better to me to just follow the ILK+ sequence and turn off the DP port
> > in .post_disable() instead. This sequence doesn't seem to suffer from
> > this problem. Could be it was always the intended sequence for DP and
> > the gen4 bspec was just never updated to include it.
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>
> The change for PCH was
>
> commit 08aff3fe26ae7a0d6f302ac2e1b7e2eb9933cd42
> Author: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Date: Mon Aug 18 22:16:09 2014 +0300
>
> drm/i915: Move DP port disable to post_disable for pch platforms
>
> where you explicitly left out g4x per modeset sequence. I guess you
> could reference that in the commit message.
>
> > ---
> > drivers/gpu/drm/i915/intel_dp.c | 26 +++++++++-----------------
> > 1 file changed, 9 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index 6068986fd985..5f09a8015c89 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -2803,16 +2803,6 @@ static void intel_disable_dp(struct intel_encoder *encoder,
> > static void g4x_disable_dp(struct intel_encoder *encoder,
> > const struct intel_crtc_state *old_crtc_state,
> > const struct drm_connector_state *old_conn_state)
> > -{
> > - intel_disable_dp(encoder, old_crtc_state, old_conn_state);
> > -
> > - /* disable the port before the pipe on g4x */
> > - intel_dp_link_down(encoder, old_crtc_state);
> > -}
> > -
> > -static void ilk_disable_dp(struct intel_encoder *encoder,
> > - const struct intel_crtc_state *old_crtc_state,
> > - const struct drm_connector_state *old_conn_state)
> > {
> > intel_disable_dp(encoder, old_crtc_state, old_conn_state);
> > }
> > @@ -2828,13 +2818,19 @@ static void vlv_disable_dp(struct intel_encoder *encoder,
> > intel_disable_dp(encoder, old_crtc_state, old_conn_state);
> > }
> >
> > -static void ilk_post_disable_dp(struct intel_encoder *encoder,
> > +static void g4x_post_disable_dp(struct intel_encoder *encoder,
> > const struct intel_crtc_state *old_crtc_state,
> > const struct drm_connector_state *old_conn_state)
> > {
> > struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
> > enum port port = encoder->port;
> >
> > + /*
> > + * Bspec does not list a specific disable sequence for g4x DP.
> > + * Follow the ilk+ sequence (disable pipe before the port) for
> > + * g4x DP as it does not suffer from underruns like the normal
> > + * g4x modeset sequence (disable pipe after the port).
> > + */
> > intel_dp_link_down(encoder, old_crtc_state);
> >
> > /* Only ilk+ has port A */
> > @@ -6450,15 +6446,11 @@ bool intel_dp_init(struct drm_i915_private *dev_priv,
> > intel_encoder->enable = vlv_enable_dp;
> > intel_encoder->disable = vlv_disable_dp;
> > intel_encoder->post_disable = vlv_post_disable_dp;
> > - } else if (INTEL_GEN(dev_priv) >= 5) {
> > - intel_encoder->pre_enable = g4x_pre_enable_dp;
> > - intel_encoder->enable = g4x_enable_dp;
> > - intel_encoder->disable = ilk_disable_dp;
> > - intel_encoder->post_disable = ilk_post_disable_dp;
> > - } else {
> > + } else{
>
> Space missing before {.
>
> The code matches the commit message, so strictly in that sense,
>
> Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Fixed up the whitespace, amended the commit message a bit with the pch
commit details, and pushed the series to dinq. Thanks for the review.
>
> but I really don't know if this is the right thing to do. Your
> call. (And your responsibility to fix the regressions! ;)
I'm feeling unusually confident about this one :)
>
>
> > intel_encoder->pre_enable = g4x_pre_enable_dp;
> > intel_encoder->enable = g4x_enable_dp;
> > intel_encoder->disable = g4x_disable_dp;
> > + intel_encoder->post_disable = g4x_post_disable_dp;
> > }
> >
> > intel_dig_port->dp.output_reg = output_reg;
>
> --
> Jani Nikula, Intel Open Source Graphics Center
--
Ville Syrjälä
Intel
