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Message-ID: <657hmty7qisg74pugmgxz4y4idze65ddozm25vnizcavqsubov@fk56ijbl23uv>
Date: Fri, 10 Jan 2025 04:10:22 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Jessica Zhang <quic_jesszhan@...cinc.com>
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 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/ .
>
> >
> > >
> > > [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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