On Fri, Nov 18, 2016 at 11:26:18AM +0100, Maarten Lankhorst wrote:
> Op 17-11-16 om 16:06 schreef Ville Syrjälä:
> > On Tue, Nov 15, 2016 at 02:53:00PM +0100, Maarten Lankhorst wrote:
> >> Op 15-11-16 om 14:41 schreef Ville Syrjälä:
> >>> On Tue, Nov 15, 2016 at 11:14:29AM +0100, Maarten Lankhorst wrote:
> >>>> Op 14-11-16 om 17:35 schreef ville.syrjala@xxxxxxxxxxxxxxx:
> >>>>> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> >>>>>
> >>>>> A modeset on one pipe can update dev_priv->atomic_cdclk_freq without
> >>>>> actually touching the hardware, in which case we won't force a modeset
> >>>>> on all the pipes, and thus won't lock any of the other pipes either.
> >>>>> That means a parallel plane update on another pipe could be looking at
> >>>>> a stale dev_priv->atomic_cdcdlk_freq and thus fail to notice when the
> >>>>> plane configuration is invalid, or potentially reject a valid update.
> >>>>>
> >>>>> To overcome this we must protect writes to atomic_cdclk_freq with
> >>>>> all the crtc locks, and thus for reads any single crtc lock will
> >>>>> be sufficient protection.
> >>>>>
> >>>>> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> >>>>> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> >>>>> ---
> >>>>> drivers/gpu/drm/i915/i915_drv.h | 9 +++++++-
> >>>>> drivers/gpu/drm/i915/intel_display.c | 41 +++++++++++++++++++++++++++++++-----
> >>>>> 2 files changed, 44 insertions(+), 6 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> >>>>> index c0f1dfc7119e..66d2950dc657 100644
> >>>>> --- a/drivers/gpu/drm/i915/i915_drv.h
> >>>>> +++ b/drivers/gpu/drm/i915/i915_drv.h
> >>>>> @@ -1874,7 +1874,14 @@ struct drm_i915_private {
> >>>>>
> >>>>> unsigned int fsb_freq, mem_freq, is_ddr3;
> >>>>> unsigned int skl_preferred_vco_freq;
> >>>>> - unsigned int cdclk_freq, max_cdclk_freq, atomic_cdclk_freq;
> >>>>> + unsigned int cdclk_freq, max_cdclk_freq;
> >>>>> +
> >>>>> + /*
> >>>>> + * For reading holding any crtc lock is sufficient,
> >>>>> + * for writing must hold all of them.
> >>>>> + */
> >>>>> + unsigned int atomic_cdclk_freq;
> >>>>> +
> >>>>> unsigned int max_dotclk_freq;
> >>>>> unsigned int rawclk_freq;
> >>>>> unsigned int hpll_freq;
> >>>>> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> >>>>> index 70f3f0b70263..d7a4bc63b05b 100644
> >>>>> --- a/drivers/gpu/drm/i915/intel_display.c
> >>>>> +++ b/drivers/gpu/drm/i915/intel_display.c
> >>>>> @@ -13946,13 +13946,32 @@ static int haswell_mode_set_planes_workaround(struct drm_atomic_state *state)
> >>>>> return 0;
> >>>>> }
> >>>>>
> >>>>> +static int intel_lock_all_pipes(struct drm_atomic_state *state)
> >>>>> +{
> >>>>> + struct drm_crtc *crtc;
> >>>>> +
> >>>>> + /* Add all pipes to the state */
> >>>>> + for_each_crtc(state->dev, crtc) {
> >>>>> + struct drm_crtc_state *crtc_state;
> >>>>> +
> >>>>> + crtc_state = drm_atomic_get_crtc_state(state, crtc);
> >>>>> + if (IS_ERR(crtc_state))
> >>>>> + return PTR_ERR(crtc_state);
> >>>>> + }
> >>>>> +
> >>>>> + return 0;
> >>>>> +}
> >>>>> +
> >>>>> static int intel_modeset_all_pipes(struct drm_atomic_state *state)
> >>>>> {
> >>>>> struct drm_crtc *crtc;
> >>>>> struct drm_crtc_state *crtc_state;
> >>>>> int ret = 0;
> >>>>>
> >>>>> - /* add all active pipes to the state */
> >>>>> + /*
> >>>>> + * Add all pipes to the state, and force
> >>>>> + * a modeset on all the active ones.
> >>>>> + */
> >>>>> for_each_crtc(state->dev, crtc) {
> >>>>> crtc_state = drm_atomic_get_crtc_state(state, crtc);
> >>>>> if (IS_ERR(crtc_state))
> >>>>> @@ -14018,12 +14037,24 @@ static int intel_modeset_checks(struct drm_atomic_state *state)
> >>>>> if (ret < 0)
> >>>>> return ret;
> >>>>>
> >>>>> + /*
> >>>>> + * Writes to dev_priv->atomic_cdclk_freq must protected by
> >>>>> + * holding all the crtc locks, even if we don't end up
> >>>>> + * touching the hardware
> >>>>> + */
> >>>>> + if (intel_state->cdclk != dev_priv->atomic_cdclk_freq) {
> >>>>> + ret = intel_lock_all_pipes(state);
> >>>>> + if (ret < 0)
> >>>>> + return ret;
> >>>>> + }
> >>>>> +
> >>>> Would it be terrible to just use intel_modeset_all_pipes here? Since this can only be different in the all crtc's disabled case
> >>>> it won't matter much.
> >>> Is there any benefit in doing that? A bit confusing IMO to force a
> >>> modeset when you don't have to.
> >>>
> >> The case where atomic cdclk changes, but dev_cdclk stays the same can only happen
> >> if you configure a crtc, but all crtc's stay !active. In all other cases dev_cdclk
> >> will change too.
> >>
> >> intel_modeset_all_pipes will only set mode_changed on active crtc's, but it will
> >> add all crtc's to the atomic state regardless to make sure the cdclk stays consistent.
> > I still don't see what the benefit is. IMO it's just confusing to say
> > that we're going to force a modeset on a disabled pipe.
> >
> if (!active || needs_modeset(crtc_state)) continue; crtc_state->mode_changed= true; It's not doing a modeset on a disabled pipe, it only makes sure it's part of the state.
But the code will still *read* if (blah) modeset_all_pipes();
which is nonsense.
--
Ville Syrjälä
Intel OTC
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