RE: [PATCH] drm/i915/cmtg: Disable CMTG after PSR exit to avoid disable timeout

On Fri, 07 Aug 2026, "Manna, Animesh" <[email protected]> wrote:
>> -----Original Message-----
>> From: Jani Nikula <[email protected]>
>> Sent: Friday, August 7, 2026 1:33 PM
>> To: Manna, Animesh <[email protected]>; intel-
>> [email protected]; [email protected]
>> Cc: Manna, Animesh <[email protected]>; Dibin Moolakadan
>> Subrahmanian <[email protected]>; Shankar,
>> Uma <[email protected]>
>> Subject: Re: [PATCH] drm/i915/cmtg: Disable CMTG after PSR exit to avoid
>> disable timeout
>> 
>> On Fri, 07 Aug 2026, Animesh Manna <[email protected]> wrote:
>> > CMTG is enabled in sync-to-port mode, so its running state
>> > (CMTG_STATE) can only clear while the port is actively timing. In
>> > hsw_crtc_disable() the CMTG was torn down at the very beginning of the
>> > sequence, before the encoders were disabled. At that point PSR may
>> > still be active on the eDP, leaving the port timing generator idle. As
>> > a result, after clearing CMTG_ENABLE the wait for CMTG_STATE to clear
>> never completes and triggers:
>> >
>> >   xe 0000:00:02.0: [drm] CMTG: A disable timeout
>> >   WARNING: drivers/gpu/drm/i915/display/intel_cmtg.c:205
>> > intel_cmtg_disable+0x331/0x3d0 [xe]
>> >
>> > This is intermittently seen with igt@kms_hdr@bpc-switch-suspend, which
>> > repeatedly cycles the eDP in and out of PSR across suspend/resume.
>> >
>> > Move the CMTG disable to after intel_encoders_disable() (so PSR is
>> > exited) but before intel_encoders_post_disable()/intel_dpll_disable(),
>> > so the transcoder timing generator and port PLL are still active while
>> > CMTG_STATE is polled. The ordering requirement of disabling CMTG
>> > before the transcoder and port PLL are brought down is preserved.
>> >
>> > Cc: Dibin Moolakadan Subrahmanian
>> > <[email protected]>
>> > Cc: Uma Shankar <[email protected]>
>> > Signed-off-by: Animesh Manna <[email protected]>
>> 
>> Fixes: ?
>> Cc: stable ?
>
> Sure, will add in next version.

If there is no next version otherwise, you don't have to and should not
send a new version just to amend these trailers. Just reply with them to
the patch.

BR,
Jani.

>
> Regards,
> Animesh
>> 
>> > ---
>> >  drivers/gpu/drm/i915/display/intel_display.c | 18 ++++++++++++++----
>> >  1 file changed, 14 insertions(+), 4 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/i915/display/intel_display.c
>> > b/drivers/gpu/drm/i915/display/intel_display.c
>> > index 829d7a411dcc..cc4d20fdda44 100644
>> > --- a/drivers/gpu/drm/i915/display/intel_display.c
>> > +++ b/drivers/gpu/drm/i915/display/intel_display.c
>> > @@ -1791,15 +1791,25 @@ static void hsw_crtc_disable(struct
>> intel_atomic_state *state,
>> >  		intel_atomic_get_old_crtc_state(state, crtc);
>> >  	struct intel_crtc *pipe_crtc;
>> >
>> > -	if (crtc->cmtg.enabled && intel_cmtg_is_allowed(old_crtc_state)) {
>> > -		intel_cmtg_set_clk_select(old_crtc_state);
>> > -		intel_cmtg_disable(old_crtc_state);
>> > -	}
>> >  	/*
>> >  	 * FIXME collapse everything to one hook.
>> >  	 * Need care with mst->ddi interactions.
>> >  	 */
>> >  	intel_encoders_disable(state, crtc);
>> > +
>> > +	/*
>> > +	 * Disable CMTG after the encoders are disabled (so PSR is exited) but
>> > +	 * before the transcoder timing generator and port PLL are torn down
>> in
>> > +	 * intel_encoders_post_disable()/intel_dpll_disable(). CMTG is
>> synced to
>> > +	 * the port, so its running state (CMTG_STATE) can only clear while
>> the
>> > +	 * port is actively timing. Doing this while PSR is still active leaves
>> > +	 * the port idle and makes the CMTG_STATE clear wait time out.
>> > +	 */
>> > +	if (crtc->cmtg.enabled && intel_cmtg_is_allowed(old_crtc_state)) {
>> > +		intel_cmtg_set_clk_select(old_crtc_state);
>> > +		intel_cmtg_disable(old_crtc_state);
>> > +	}
>> > +
>> >  	intel_encoders_post_disable(state, crtc);
>> >
>> >  	intel_dpll_disable(old_crtc_state);
>> 
>> --
>> Jani Nikula, Intel

-- 
Jani Nikula, Intel