Re: [PATCH 8/9] drm/i915/dp: Protect link training with connection mutex

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

On Thu, Sep 14, 2017 at 03:26:37PM -0700, Ausmus, James wrote:
> On Tue, Sep 12, 2017 at 4:57 PM, Dhinakaran Pandiyan
> <dhinakaran.pandiyan@intel.com> wrote:
> > The other instances of link training are protected with
> > connection_mutex, so do the same in check_mst_status() too.
> 
> We don't seem to be taking connection_mutex around
> intel_dp_start/stop_link_train in the intel_enable_dp or
> intel_ddi_pre_enable_dp paths (unless it's taken higher in the stack)
> - is it needed in all instances?
>

intel_ddi_pre_enable_dp() gets called from the crtc_enable hook higher
up in the stack which gets called essentially from atomic_commit() hook
that traces back eventually to the drm_mode_setcrtc call that grabs the
mod_config mutex there: mutex_lock(&crtc->dev->mode_config.mutex);

Manasi

> >
> > Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index aab9ba31f79e..644463ba313e 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -4191,6 +4191,7 @@ static void intel_dp_handle_test_request(struct intel_dp *intel_dp)
> >  static int
> >  intel_dp_check_mst_status(struct intel_dp *intel_dp)
> >  {
> > +       struct drm_device *dev = intel_dp_to_dev(intel_dp);
> >         bool bret;
> >         u8 esi[DP_DPRX_ESI_LEN] = { 0 };
> >         int ret = 0;
> > @@ -4205,8 +4206,11 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
> >                 if (intel_dp->active_mst_links &&
> >                     !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
> >                         DRM_DEBUG_KMS("channel EQ not ok, retraining\n");
> > +
> > +                       drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> >                         intel_dp_start_link_train(intel_dp);
> >                         intel_dp_stop_link_train(intel_dp);
> > +                       drm_modeset_unlock(&dev->mode_config.connection_mutex);
> >                 }
> >
> >                 DRM_DEBUG_KMS("got esi %3ph\n", esi);
> > --
> > 2.11.0
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> 
> 
> -- 
> 
> 
> James Ausmus
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
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