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Date: Thu, 27 Oct 2022 20:40:35 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Vinod Polimera <vpolimer@....qualcomm.com>,
"Vinod Polimera (QUIC)" <quic_vpolimer@...cinc.com>,
"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
"freedreno@...ts.freedesktop.org" <freedreno@...ts.freedesktop.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"robdclark@...il.com" <robdclark@...il.com>,
"dianders@...omium.org" <dianders@...omium.org>,
"swboyd@...omium.org" <swboyd@...omium.org>,
"Kalyan Thota (QUIC)" <quic_kalyant@...cinc.com>,
"Kuogee Hsieh (QUIC)" <quic_khsieh@...cinc.com>,
"Vishnuvardhan Prodduturi (QUIC)" <quic_vproddut@...cinc.com>,
"Bjorn Andersson (QUIC)" <quic_bjorande@...cinc.com>,
"Aravind Venkateswaran (QUIC)" <quic_aravindh@...cinc.com>,
"Abhinav Kumar (QUIC)" <quic_abhinavk@...cinc.com>,
"Sankeerth Billakanti (QUIC)" <quic_sbillaka@...cinc.com>
Subject: Re: [PATCH v8 01/15] drm/msm/disp/dpu: clear dpu_assign_crtc and get
crtc from connector state instead of dpu_enc
On 27/10/2022 16:34, Vinod Polimera wrote:
>> -----Original Message-----
>> From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>> Sent: Monday, October 24, 2022 8:52 PM
>> To: Vinod Polimera (QUIC) <quic_vpolimer@...cinc.com>; dri-
>> devel@...ts.freedesktop.org; linux-arm-msm@...r.kernel.org;
>> freedreno@...ts.freedesktop.org; devicetree@...r.kernel.org
>> Cc: linux-kernel@...r.kernel.org; robdclark@...il.com;
>> dianders@...omium.org; swboyd@...omium.org; Kalyan Thota (QUIC)
>> <quic_kalyant@...cinc.com>; Kuogee Hsieh (QUIC)
>> <quic_khsieh@...cinc.com>; Vishnuvardhan Prodduturi (QUIC)
>> <quic_vproddut@...cinc.com>; Bjorn Andersson (QUIC)
>> <quic_bjorande@...cinc.com>; Aravind Venkateswaran (QUIC)
>> <quic_aravindh@...cinc.com>; Abhinav Kumar (QUIC)
>> <quic_abhinavk@...cinc.com>; Sankeerth Billakanti (QUIC)
>> <quic_sbillaka@...cinc.com>
>> Subject: Re: [PATCH v8 01/15] drm/msm/disp/dpu: clear dpu_assign_crtc and
>> get crtc from connector state instead of dpu_enc
>>
>> WARNING: This email originated from outside of Qualcomm. Please be wary
>> of any links or attachments, and do not enable macros.
>>
>> On 12/10/2022 15:02, Vinod Polimera wrote:
>>> Update crtc retrieval from dpu_enc to dpu_enc connector state,
>>> since new links get set as part of the dpu enc virt mode set.
>>> The dpu_enc->crtc cache is no more needed, hence cleaning it as
>>> part of this change.
>>>
>>> Signed-off-by: Vinod Polimera <quic_vpolimer@...cinc.com>
>>> ---
>>> drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 4 ---
>>> drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 42 +++++++++---------
>> -----------
>>> drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.h | 8 ------
>>> 3 files changed, 13 insertions(+), 41 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>>> index 13ce321..8ec9a13 100644
>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>>> @@ -1029,7 +1029,6 @@ static void dpu_crtc_disable(struct drm_crtc *crtc,
>>> */
>>> if (dpu_encoder_get_intf_mode(encoder) == INTF_MODE_VIDEO)
>>> release_bandwidth = true;
>>> - dpu_encoder_assign_crtc(encoder, NULL);
>>> }
>>>
>>> /* wait for frame_event_done completion */
>>> @@ -1099,9 +1098,6 @@ static void dpu_crtc_enable(struct drm_crtc *crtc,
>>> trace_dpu_crtc_enable(DRMID(crtc), true, dpu_crtc);
>>> dpu_crtc->enabled = true;
>>>
>>> - drm_for_each_encoder_mask(encoder, crtc->dev, crtc->state-
>>> encoder_mask)
>>> - dpu_encoder_assign_crtc(encoder, crtc);
>>> -
>>> /* Enable/restore vblank irq handling */
>>> drm_crtc_vblank_on(crtc);
>>> }
>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>>> index 9c6817b..d05b353 100644
>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
>>> @@ -132,11 +132,6 @@ enum dpu_enc_rc_states {
>>> * @intfs_swapped: Whether or not the phys_enc interfaces have been
>> swapped
>>> * for partial update right-only cases, such as pingpong
>>> * split where virtual pingpong does not generate IRQs
>>> - * @crtc: Pointer to the currently assigned crtc. Normally you
>>> - * would use crtc->state->encoder_mask to determine the
>>> - * link between encoder/crtc. However in this case we need
>>> - * to track crtc in the disable() hook which is called
>>> - * _after_ encoder_mask is cleared.
>>> * @connector: If a mode is set, cached pointer to the active
>> connector
>>> * @crtc_kickoff_cb: Callback into CRTC that will flush & start
>>> * all CTL paths
>>> @@ -181,7 +176,6 @@ struct dpu_encoder_virt {
>>>
>>> bool intfs_swapped;
>>>
>>> - struct drm_crtc *crtc;
>>> struct drm_connector *connector;
>>>
>>> struct dentry *debugfs_root;
>>> @@ -1288,7 +1282,7 @@ static void dpu_encoder_vblank_callback(struct
>> drm_encoder *drm_enc,
>>> struct dpu_encoder_phys *phy_enc)
>>> {
>>> struct dpu_encoder_virt *dpu_enc = NULL;
>>> - unsigned long lock_flags;
>>> + struct drm_crtc *crtc;
>>>
>>> if (!drm_enc || !phy_enc)
>>> return;
>>> @@ -1296,12 +1290,13 @@ static void dpu_encoder_vblank_callback(struct
>> drm_encoder *drm_enc,
>>> DPU_ATRACE_BEGIN("encoder_vblank_callback");
>>> dpu_enc = to_dpu_encoder_virt(drm_enc);
>>>
>>> - atomic_inc(&phy_enc->vsync_cnt);
>>> + if (!dpu_enc->connector || !dpu_enc->connector->state ||
>>> + !dpu_enc->connector->state->crtc)
>>> + return;
>>>
>>> - spin_lock_irqsave(&dpu_enc->enc_spinlock, lock_flags);
>>> - if (dpu_enc->crtc)
>>> - dpu_crtc_vblank_callback(dpu_enc->crtc);
>>> - spin_unlock_irqrestore(&dpu_enc->enc_spinlock, lock_flags);
>>> + atomic_inc(&phy_enc->vsync_cnt);
>>> + crtc = dpu_enc->connector->state->crtc;
>>> + dpu_crtc_vblank_callback(crtc);
>>
>> So, what if the user commits the mode setting change on another CPU,
>> while we are handling the vblank callback here? Can this happen?
>>
> If user issues a commit on another CPU, it will wait in the drm_atomic_helper_swap_state
> as drm_atomic_helper_commit_hw_done which does the complete_all(&commit->hw_done)
> for the current commit didn't finish yet.
Yes. But there is no interlock between commit->hw_done and vblank IRQ
processing, isn't it? This call happens when DPU processes the vblank
IRQ, so nobody stops other core from swapping the encode state on
another core.
>>>
>>> DPU_ATRACE_END("encoder_vblank_callback");
>>> }
>> --
>> With best wishes
>> Dmitry
>
> Thanks,
> Vinod P.
--
With best wishes
Dmitry
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