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Message-ID: <92666877-1a88-4590-9adc-15cd7b4af06a@quicinc.com>
Date: Fri, 10 Jan 2025 14:08:52 -0800
From: Jessica Zhang <quic_jesszhan@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Rob Clark <robdclark@...il.com>, <quic_abhinavk@...cinc.com>,
Sean Paul
<sean@...rly.run>,
Marijn Suijten <marijn.suijten@...ainline.org>,
"David
Airlie" <airlied@...il.com>,
Maarten Lankhorst
<maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
Simona Vetter <simona@...ll.ch>,
Simona Vetter <simona.vetter@...ll.ch>, <quic_ebharadw@...cinc.com>,
<linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
<freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
Rob Clark
<robdclark@...omium.org>,
Ville Syrjälä
<ville.syrjala@...ux.intel.com>
Subject: Re: [PATCH v4 15/25] drm/msm/dpu: Add CWB to msm_display_topology
On 1/9/2025 6:10 PM, Dmitry Baryshkov wrote:
> On Thu, Jan 09, 2025 at 05:50:16PM -0800, Jessica Zhang wrote:
>>
>>
>> On 1/9/2025 5:42 PM, Dmitry Baryshkov wrote:
>>> On Fri, 10 Jan 2025 at 02:30, Jessica Zhang <quic_jesszhan@...cinc.com> wrote:
>>>>
>>>>
>>>>
>>>> On 1/9/2025 4:00 PM, Dmitry Baryshkov wrote:
>>>>> On Thu, Jan 09, 2025 at 02:34:44PM -0800, Jessica Zhang wrote:
>>>>>>
>>>>>>
>>>>>> On 1/3/2025 10:16 AM, Dmitry Baryshkov wrote:
>>>>>>> On Fri, Jan 03, 2025 at 10:03:35AM -0800, Jessica Zhang wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> On 12/19/2024 9:03 PM, Dmitry Baryshkov wrote:
>>>>>>>>> On Mon, Dec 16, 2024 at 04:43:26PM -0800, Jessica Zhang wrote:
>>>>>>>>>> Add the cwb_enabled flag to msm_display topology and adjust the toplogy
>>>>>>>>>> to account for concurrent writeback
>>>>>>>>>
>>>>>>>>> Why?
>>>>>>>>
>>>>>>>> Hi Dmitry,
>>>>>>>>
>>>>>>>> This flag is necessary to specify that CWB mux(es) need to be assigned for
>>>>>>>> the given reqeusted topology.
>>>>>>>
>>>>>>> Why is necessary? Please rephrase your statement (we need foo bar, so do
>>>>>>> baz).
>>>>>>
>>>>>> Ack, what do you think of rephrasing the commit msg to this:
>>>>>>
>>>>>> ```
>>>>>> Add support for adjusting topology based on if concurrent writeback is
>>>>>> enabled.
>>>>>>
>>>>>> Currently, the topology is calculated based on the assumption that the user
>>>>>> cannot request real-time and writeback simultaneously. For example, the
>>>>>> number of LMs and CTLs are currently based off the number of phys encoders
>>>>>> under the assumption there will be at least 1 LM/CTL per phys encoder.
>>>>>>
>>>>>> This will not hold true for concurrent writeback as 2 phys encoders (1
>>>>>> real-time and 1 writeback) can be driven by 1 LM/CTL when concurrent
>>>>>> writeback is enabled.
>>>>>>
>>>>>> To account for this, add a cwb_enabled flag and only adjust the number of
>>>>>> CTL/LMs needed by a given topology based on the number of phys encoders only
>>>>>> if CWB is not enabled.
>>>>>>
>>>>>> ```
>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
>>>>>>>>>> ---
>>>>>>>>>> drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 11 ++++++++++-
>>>>>>>>>> drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 10 ++++++++--
>>>>>>>>>> drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h | 2 ++
>>>>>>>>>> 3 files changed, 20 insertions(+), 3 deletions(-)
>>>>>>>>>>
>>>>>>>>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>>>>>>>>>> index b4bfded3d53025853cee112ca598533ece290318..b063c8fe4c0594772d84401fa56c9c21afc0ad18 100644
>>>>>>>>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>>>>>>>>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>>>>>>>>>> @@ -1198,6 +1198,8 @@ static struct msm_display_topology dpu_crtc_get_topology(
>>>>>>>>>> dpu_encoder_update_topology(drm_enc, &topology, crtc_state->state,
>>>>>>>>>> &crtc_state->adjusted_mode);
>>>>>>>>>> + topology.cwb_enabled = drm_crtc_in_clone_mode(crtc_state);
>>>>>>>>>> +
>>>>>>>>>> /*
>>>>>>>>>> * Datapath topology selection
>>>>>>>>>> *
>>>>>>>>>> @@ -1209,9 +1211,16 @@ static struct msm_display_topology dpu_crtc_get_topology(
>>>>>>>>>> * 2 LM, 1 INTF (stream merge to support high resolution interfaces)
>>>>>>>>>> *
>>>>>>>>>> * Add dspps to the reservation requirements if ctm is requested
>>>>>>>>>> + *
>>>>>>>>>> + * Only hardcode num_lm to 2 for cases where num_intf == 2 and CWB is not
>>>>>>>>>> + * enabled. This is because in cases where CWB is enabled, num_intf will
>>>>>>>>>> + * count both the WB and real-time phys encoders.
>>>>>>>>>> + *
>>>>>>>>>> + * For non-DSC CWB usecases, have the num_lm be decided by the
>>>>>>>>>> + * (mode->hdisplay > MAX_HDISPLAY_SPLIT) check.
>>>>>>>>>> */
>>>>>>>>>> - if (topology.num_intf == 2)
>>>>>>>>>> + if (topology.num_intf == 2 && !topology.cwb_enabled)
>>>>>>>>>> topology.num_lm = 2;
>>>>>>>>>> else if (topology.num_dsc == 2)
>>>>>>>>>> topology.num_lm = 2;
>>>>>>>>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
>>>>>>>>>> index b763ef19f4c60ae8a35df6a6ffb19e8411bc63f8..85adaf256b2c705d2d7df378b6ffc0e578f52bc3 100644
>>>>>>>>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
>>>>>>>>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
>>>>>>>>>> @@ -382,8 +382,14 @@ static int _dpu_rm_reserve_ctls(
>>>>>>>>>> int i = 0, j, num_ctls;
>>>>>>>>>> bool needs_split_display;
>>>>>>>>>> - /* each hw_intf needs its own hw_ctrl to program its control path */
>>>>>>>>>> - num_ctls = top->num_intf;
>>>>>>>>>> + /*
>>>>>>>>>> + * For non-CWB mode, each hw_intf needs its own hw_ctl to program its
>>>>>>>>>> + * control path. Hardcode num_ctls to 1 if CWB is enabled
>>>>>>>>>> + */
>>>>>>>>>
>>>>>>>>> Why?
>>>>>>>>
>>>>>>>> This is because num_intf is based on the number of phys_encs. Since in the
>>>>>>>> CWB case, the WB and real-time encoders will be driven by the same CTL. I
>>>>>>>> can add this to the comment doc.
>>>>>>>
>>>>>>> Why are they driven by the same CTL? Is it also the case for platforms
>>>>>>> before DPU 5.x?
>>>>>>
>>>>>> This is because the WB and real-time path for a given topology would be
>>>>>> driven by the same data path so the same CTL should enable the real-time and
>>>>>> WB active bits.
>>>>>>
>>>>>> This is the same for pre-DPU 5.x.
>>>>>
>>>>> But pre-5.x platforms didn't have ACTIVE_CTL, so they should be using
>>>>> separte CTL for each of the physical encoders.
>>>>
>>>> For pre-DPU 5.x, enabling CWB would mean configuring the registers under
>>>> both the WB and MODE_SEL_* cases here [1]
>>>
>>> But do we still have to use a single CTL or would we use two different
>>> CTLs, one for the main output and one for WB?
>>
>> We would have to enable both WB and the real-time output on the same CTL
>
> Thanks for the confirmation. Then the text your wrote above should be
> mostly okay. Please drop the first ("Add support...") sentence and s/can
> be driven by/must be driven by/ .
Ack, sounds good
>
>>
>>>
>>>>
>>>> [1]
>>>> https://elixir.bootlin.com/linux/v6.12.6/source/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_ctl.c#L588
>>>>
>>>>>
>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>> Jessica Zhang
>>>>>>>>
>>>>>>>>>
>>>>>>>>>> + if (top->cwb_enabled)
>>>>>>>>>> + num_ctls = 1;
>>>>>>>>>> + else
>>>>>>>>>> + num_ctls = top->num_intf;
>>>>>>>>>> needs_split_display = _dpu_rm_needs_split_display(top);
>>>>>>>>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
>>>>>>>>>> index b061dfdab52e04ab7d777e912a30173273cb3db7..12db21a2403ec6930894c36a58e898c5d94c2568 100644
>>>>>>>>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
>>>>>>>>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
>>>>>>>>>> @@ -46,6 +46,7 @@ struct dpu_rm {
>>>>>>>>>> * @num_dspp: number of dspp blocks used
>>>>>>>>>> * @num_dsc: number of Display Stream Compression (DSC) blocks used
>>>>>>>>>> * @needs_cdm: indicates whether cdm block is needed for this display topology
>>>>>>>>>> + * @cwb_enabled: indicates whether CWB is enabled for this display topology
>>>>>>>>>> */
>>>>>>>>>> struct msm_display_topology {
>>>>>>>>>> u32 num_lm;
>>>>>>>>>> @@ -53,6 +54,7 @@ struct msm_display_topology {
>>>>>>>>>> u32 num_dspp;
>>>>>>>>>> u32 num_dsc;
>>>>>>>>>> bool needs_cdm;
>>>>>>>>>> + bool cwb_enabled;
>>>>>>>>>> };
>>>>>>>>>> int dpu_rm_init(struct drm_device *dev,
>>>>>>>>>>
>>>>>>>>>> --
>>>>>>>>>> 2.34.1
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> --
>>>>>>>>> With best wishes
>>>>>>>>> Dmitry
>>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> With best wishes
>>>>>>> Dmitry
>>>>>>
>>>>>
>>>>> --
>>>>> With best wishes
>>>>> Dmitry
>>>>
>>>
>>>
>>> --
>>> With best wishes
>>> Dmitry
>>
>
> --
> With best wishes
> Dmitry
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