Message-ID: <90e91cd7-e5d7-4d0f-aef8-e19b9f0e336b@quicinc.com>
Date: Tue, 4 Mar 2025 15:43:43 -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 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.

>> 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.

>>
>>>>
>>>> [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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