Message-ID: <3cd320d3-1ed2-45a7-91eb-bf6c1abdfbd6@quicinc.com>
Date: Tue, 4 Mar 2025 20:02:24 -0800
From: Abhinav Kumar <quic_abhinavk@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Jessica Zhang <quic_jesszhan@...cinc.com>,
        Rob Clark
	<robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn Suijten
	<marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, "Simona
 Vetter" <simona@...ll.ch>,
        <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] drm/msm/dpu: Force modeset if new CTLs have been
 reserved



On 3/4/2025 7:09 PM, Dmitry Baryshkov wrote:
> On Wed, 5 Mar 2025 at 00:43, Abhinav Kumar <quic_abhinavk@...cinc.com> wrote:
>>
>>
>>
>> On 3/4/2025 12:42 PM, Dmitry Baryshkov wrote:
>>> On Tue, Mar 04, 2025 at 11:38:24AM -0800, Abhinav Kumar wrote:
>>>>
>>>>
>>>> On 3/3/2025 9:32 PM, Dmitry Baryshkov wrote:
>>>>> On Tue, 4 Mar 2025 at 03:44, Jessica Zhang <quic_jesszhan@...cinc.com> wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 3/3/2025 3:49 PM, Dmitry Baryshkov wrote:
>>>>>>> On Mon, Mar 03, 2025 at 10:28:00AM -0800, Jessica Zhang wrote:
>>>>>>>> If new CTLs are reserved by CRTC but atomic_enable() is skipped, the
>>>>>>>> encoders will configure the stale CTL instead of the newly reserved one.
>>>>>>>
>>>>>>> The CTLs are propagates in .atomic_mode_set(), not in .atomic_enable().
>>>>>>
>>>>>> Hi Dmitry,
>>>>>>
>>>>>> Yes, sorry mixed up the two function ops here and in my reply in the CWB
>>>>>> thread.
>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>> Avoid this by setting mode_changed to true if new CTLs have been
>>>>>>>> reserved by CRTC.
>>>>>>>
>>>>>>> This looks very strange. First we reserve new CTLs when there is a
>>>>>>> modeset requested. Then on one of the next commits we detect that
>>>>>>> encoder has stale CTLs and try to upgrade the commit to full modeset
>>>>>>> (while the user might not have .allow_modeset set to true for whatever
>>>>>>> reason, e.g. because only ACTIVE is changed).
>>>>>>
>>>>>> Ah I see what you mean. I think this is an issue with how/when we're
>>>>>> calling dpu_rm_reserve(). Since RM reservation is tied to
>>>>>> atomic_check(), we aren't able to force a modeset based on HW block
>>>>>> reservation. The only reason we were able to avoid this issue with
>>>>>> needs_cdm is because needs_cdm didn't depend on the CDM HW block index.
>>>>>>
>>>>>> I think there's not really a good way to avoid this other than flipping
>>>>>> the order of the msm_atomic_check to drm_helper_atomic_check ->
>>>>>> dpu_kms.check_mode_changed -> drm_atomic_helper_check_modeset().
>>>>>
>>>>> No-no-no. This would require a full drm_atomic_helper_check() call
>>>>> again, after the check_mode_changed() callback. But again, this should
>>>>> not be required at all. The whole point of .check_mode_changed() is to
>>>>> be called before performing full atomic_check() chains.
>>>>>
>>>>
>>>> Right but the documentation also allows calling
>>>> drm_atomic_helper_check_modeset() again. We are looking at all options even
>>>> moving forward and not just this issue.
>>>
>>> It does. But I'd rather not do it. Especially not in this case: we
>>> perfectly know in advance if hw resources were reallocated or not.
>>>
>>>>
>>>>>>
>>>>>> What do you think? It seems to be valid given the examples in the DRM
>>>>>> docs [1]
>>>>>>
>>>>>> [1]
>>>>>> https://elixir.bootlin.com/linux/v6.13.5/source/drivers/gpu/drm/drm_atomic_helper.c#L610
>>>>>>
>>>>>>>
>>>>>>> Could you please check if the following change fixes the issue: in
>>>>>>> crtc_set_mode() replace the raw !new_crtc_state->mode_changed check with
>>>>>>> the drm_atomic_crtc_needs_modeset() call?
>>>>>>
>>>>>> This also fixes the DPMS failures. IIRC Abhinav had suggested a similar
>>>>>> change to fix a different issue [2] and you gave some feedback on
>>>>>> avoiding mode_set() for enable/disable calls which don't have mode_changed.
>>>>>
>>>>> After reading the documentation for
>>>>> drm_encoder_helper_funcs.atomic_mode_set() and looking around, I think
>>>>> the issue is in the handling of the DPMS functions. I might have a fix
>>>>> for the issue.
>>>>>
>>>>>> Also, while this may fix the CWB CI failures, wouldn't the issue still
>>>>>> remain regarding how to force modeset for changes in HW block reservation?
>>>>>
>>>>> I think it is the other way around: HW block reservation is only
>>>>> changed if there is a modeset. I'm currently testing my theory :-) We
>>>>> were performing HW reassignment if drm_atomic_crtc_needs_modeset() was
>>>>> true. However this function returns true in one of the cases, where
>>>>> there is no actual modeset happening (and it's even documented this
>>>>> way) - when only DPMS call has happened (in other words, when
>>>>> .active_changed = true, but two other bits are false). It is required
>>>>> not to reassign HW resources in such a case. So, I think, a correct
>>>>> fix is to change the condition in dpu_crtc_atomic_check().
>>>>>
>>>>
>>>> Yes, Jessica had also suggested this option. This will work because now the
>>>> resource re-assignment will not happen and hence will avoid the issue. The
>>>> documentation of DPMS was not fully clear. So it said, the same thing you
>>>> mentioned, that when active has changed there is no need to reassign
>>>> hardware resources but I was not sure if that would impact normal
>>>> suspend/resume because across suspend/resume hardware resources need to be
>>>> cleared / re-assigned.
>>>
>>> Suspend / resume is handled via the helpers, which commit an
>>> all-disabled state and then commit a previous state. Other than that,
>>> there is no need to clear resource assignments during suspend resume.
>>> They should be disabled, but there is no need to drop the assignment.
>>>
>>
>> We will need to do some testing to make sure this does not introduce
>> some other regressions. You can post your change, we can discuss it there.
> 
> Posted in another thread.
> 
>>
>>>> I do still think that, even if this also works, we
>>>> will still run into issues when we will need to force a mode_changed based
>>>> on resource assignment of other encoder based blocks such as DSC or PP etc.
>>>
>>> This is what dpu_encoder_needs_modeset() is for. On the other hand,
>>> note, if we reassigned resources, it means that either mode_changes or
>>> connectors_changed is set. And the DRM framework will call encoder's
>>> atomic_mode_set() in such a case.
>>>
>>
>> Like we wrote, dpu_encoder_needs_modeset() is not useful without the
>> sequence change in msm_atomic_check because dpu_encoder_needs_modeset()
>> is called before the resource assignments are done today.
> 
> Resources are reassigned if the mode_changed or connector_changed is
> true. There are no other ways to reassign resources.  Under these
> circumstances the encoder's atomic_mode_set() callback is called,
> propagating those changes to the encoder. What is the problem that you
> are trying to solve here?
> 

Thats fine. We will re-test the patch for some more cases and move fwd 
with that.

>>
>>>>
>>>>>>
>>>>>> [2] https://gitlab.freedesktop.org/drm/msm/-/issues/59
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Jessica Zhang
>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>> Note: This patch only adds tracking for the CTL reservation, but eventually
>>>>>>>> all HW blocks used by encoders (i.e. DSC, PINGPONG, CWB) should have a
>>>>>>>> similar check to avoid the same issue.
>>>>>>>>
>>>>>>>> Suggested-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
>>>>>>>> Closes: https://lists.freedesktop.org/archives/freedreno/2025-February/036719.html
>>>>>>>> Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
>>>>>>>> ---
>>>>>>>>      drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c    | 13 +++++++++++++
>>>>>>>>      drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 12 ++++++++++++
>>>>>>>>      drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h |  1 +
>>>>>>>>      3 files changed, 26 insertions(+)
>>>>>>>>
>>>>>>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>>>>>>>> index 4073d821158c0..a1a8be8f5ab9f 100644
>>>>>>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>>>>>>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>>>>>>>> @@ -1406,19 +1406,32 @@ int dpu_crtc_check_mode_changed(struct drm_crtc_state *old_crtc_state,
>>>>>>>>         struct drm_crtc *crtc = new_crtc_state->crtc;
>>>>>>>>         bool clone_mode_enabled = drm_crtc_in_clone_mode(old_crtc_state);
>>>>>>>>         bool clone_mode_requested = drm_crtc_in_clone_mode(new_crtc_state);
>>>>>>>> +    struct dpu_crtc_state *cstate = to_dpu_crtc_state(new_crtc_state);
>>>>>>>> +    uint32_t enc_ctl_mask = 0;
>>>>>>>> +    uint32_t crtc_ctl_mask = 0;
>>>>>>>> +    struct dpu_crtc_mixer *m;
>>>>>>>>
>>>>>>>>         DRM_DEBUG_ATOMIC("%d\n", crtc->base.id);
>>>>>>>>
>>>>>>>> +    for (int i = 0; i < cstate->num_mixers; i++) {
>>>>>>>> +            m = &cstate->mixers[i];
>>>>>>>> +            crtc_ctl_mask |= BIT(m->lm_ctl->idx - CTL_0);
>>>>>>>> +    }
>>>>>>>> +
>>>>>>>>         /* there might be cases where encoder needs a modeset too */
>>>>>>>>         drm_for_each_encoder_mask(drm_enc, crtc->dev, new_crtc_state->encoder_mask) {
>>>>>>>>                 if (dpu_encoder_needs_modeset(drm_enc, new_crtc_state->state))
>>>>>>>>                         new_crtc_state->mode_changed = true;
>>>>>>>> +            enc_ctl_mask |= dpu_encoder_get_ctls(drm_enc);
>>>>>>>>         }
>>>>>>>>
>>>>>>>>         if ((clone_mode_requested && !clone_mode_enabled) ||
>>>>>>>>             (!clone_mode_requested && clone_mode_enabled))
>>>>>>>>                 new_crtc_state->mode_changed = true;
>>>>>>>>
>>>>>>>> +    if (crtc_ctl_mask != enc_ctl_mask)
>>>>>>>> +            new_crtc_state->mode_changed = true;
>>>>>>>> +
>>>>>>>>         return 0;
>>>>>>>>      }
>>>>>>>>
>>>>>>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>>>>>>>> index a61598710acda..2f3101caeba91 100644
>>>>>>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>>>>>>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>>>>>>>> @@ -188,6 +188,7 @@ struct dpu_encoder_virt {
>>>>>>>>
>>>>>>>>         unsigned int dsc_mask;
>>>>>>>>         unsigned int cwb_mask;
>>>>>>>> +    unsigned int ctl_mask;
>>>>>>>>
>>>>>>>>         bool intfs_swapped;
>>>>>>>>
>>>>>>>> @@ -707,6 +708,13 @@ void dpu_encoder_update_topology(struct drm_encoder *drm_enc,
>>>>>>>>         }
>>>>>>>>      }
>>>>>>>>
>>>>>>>> +uint32_t dpu_encoder_get_ctls(struct drm_encoder *drm_enc)
>>>>>>>> +{
>>>>>>>> +    struct dpu_encoder_virt *dpu_enc = to_dpu_encoder_virt(drm_enc);
>>>>>>>> +
>>>>>>>> +    return dpu_enc->ctl_mask;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>>      bool dpu_encoder_needs_modeset(struct drm_encoder *drm_enc, struct drm_atomic_state *state)
>>>>>>>>      {
>>>>>>>>         struct drm_connector *connector;
>>>>>>>> @@ -1155,6 +1163,7 @@ static void dpu_encoder_virt_atomic_mode_set(struct drm_encoder *drm_enc,
>>>>>>>>         bool is_cwb_encoder;
>>>>>>>>         unsigned int dsc_mask = 0;
>>>>>>>>         unsigned int cwb_mask = 0;
>>>>>>>> +    unsigned int ctl_mask = 0;
>>>>>>>>         int i;
>>>>>>>>
>>>>>>>>         if (!drm_enc) {
>>>>>>>> @@ -1245,11 +1254,14 @@ static void dpu_encoder_virt_atomic_mode_set(struct drm_encoder *drm_enc,
>>>>>>>>                                 "no ctl block assigned at idx: %d\n", i);
>>>>>>>>                         return;
>>>>>>>>                 }
>>>>>>>> +            ctl_mask |= BIT(phys->hw_ctl->idx - CTL_0);
>>>>>>>>
>>>>>>>>                 phys->cached_mode = crtc_state->adjusted_mode;
>>>>>>>>                 if (phys->ops.atomic_mode_set)
>>>>>>>>                         phys->ops.atomic_mode_set(phys, crtc_state, conn_state);
>>>>>>>>         }
>>>>>>>> +
>>>>>>>> +    dpu_enc->ctl_mask = ctl_mask;
>>>>>>>>      }
>>>>>>>>
>>>>>>>>      static void _dpu_encoder_virt_enable_helper(struct drm_encoder *drm_enc)
>>>>>>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
>>>>>>>> index ca1ca2e51d7ea..70b03743dc346 100644
>>>>>>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
>>>>>>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h
>>>>>>>> @@ -91,6 +91,7 @@ bool dpu_encoder_needs_modeset(struct drm_encoder *drm_enc, struct drm_atomic_st
>>>>>>>>
>>>>>>>>      void dpu_encoder_prepare_wb_job(struct drm_encoder *drm_enc,
>>>>>>>>                 struct drm_writeback_job *job);
>>>>>>>> +uint32_t dpu_encoder_get_ctls(struct drm_encoder *drm_enc);
>>>>>>>>
>>>>>>>>      void dpu_encoder_cleanup_wb_job(struct drm_encoder *drm_enc,
>>>>>>>>                 struct drm_writeback_job *job);
>>>>>>>>
>>>>>>>> ---
>>>>>>>> base-commit: 866e43b945bf98f8e807dfa45eca92f931f3a032
>>>>>>>> change-id: 20250228-force-modeset-hw-ctl-d02b80a2bb4c
>>>>>>>> prerequisite-change-id: 20241222-drm-dirty-modeset-88079bd27ae6:v2
>>>>>>>> prerequisite-patch-id: 0c61aabfcd13651203f476985380cbf4d3c299e6
>>>>>>>> prerequisite-patch-id: c6026f08011c288fd301676e9fa6f46d0cc1dab7
>>>>>>>> prerequisite-patch-id: b0cb06d5c88791d6e4755d879ced0d5050aa3cbf
>>>>>>>> prerequisite-patch-id: fd72ddde9dba0df053113bc505c213961a9760da
>>>>>>>> prerequisite-change-id: 20250209-dpu-c3fac78fc617:v2
>>>>>>>> prerequisite-patch-id: c84d2b4b06be06384968429085d1e8ebae23a583
>>>>>>>> prerequisite-patch-id: fb8ea7b9e7c85fabd27589c6551108382a235002
>>>>>>>> prerequisite-change-id: 20250211-dither-disable-b77b1e31977f:v1
>>>>>>>> prerequisite-patch-id: 079e04296212b4b83d51394b5a9b5eea6870d98a
>>>>>>>> prerequisite-change-id: 20240618-concurrent-wb-97d62387f952:v6
>>>>>>>> prerequisite-patch-id: b52034179741dc182aea9411fd446e270fdc69d1
>>>>>>>> prerequisite-patch-id: bc472765a7d5214691f3d92696cc8b0119f3252e
>>>>>>>> prerequisite-patch-id: c959bc480e96b04297ebaf30fea3a68bbac69da6
>>>>>>>> prerequisite-patch-id: f7db8449b241a41faac357d9257f8c7cb16503ec
>>>>>>>> prerequisite-patch-id: 7beb73131d0ab100f266fcd3c1f67c818a3263f4
>>>>>>>> prerequisite-patch-id: c08cbb5cf4e67e308afd61fdad6684b89429d3b6
>>>>>>>> prerequisite-patch-id: a4e343143b8fbe98ae4aa068cc459c750105eb9d
>>>>>>>> prerequisite-patch-id: 1d09edcf12ef7e7ab43547eefacae5b604b698e9
>>>>>>>> prerequisite-patch-id: 0008f9802bfd3c5877267666cceb7608203e5830
>>>>>>>> prerequisite-patch-id: 49402eb767c97915faf2378c5f5d05ced2dcfdac
>>>>>>>> prerequisite-patch-id: 522be2a6b5fe4e3a2d609526bb1539f9bc6f828f
>>>>>>>> prerequisite-patch-id: 031da00d0fffd522f74d682a551362f3ecda0c71
>>>>>>>> prerequisite-patch-id: 9454cec22231a8f3f01c33d52a5df3e26dd88287
>>>>>>>> prerequisite-patch-id: 7edbeaace3549332e581bee3183a76b0e4d18163
>>>>>>>>
>>>>>>>> Best regards,
>>>>>>>> --
>>>>>>>> Jessica Zhang <quic_jesszhan@...cinc.com>
>>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> With best wishes
>>>>>>> Dmitry
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
> 
> 

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