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

[Ausmus, James]

On Fri, Sep 15, 2017 at 11:38 AM, Manasi Navare
<manasi.d.navare at intel.com> wrote:
> 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 at 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);

Got it - thanks for the pointer!

-James

>
> Manasi
>
>> >
>> > Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at 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 at lists.freedesktop.org
>> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>>
>>
>>
>> --
>>
>>
>> James Ausmus
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/intel-gfx



-- 


James Ausmus