From: Marijn Suijten <marijn.suijten@somainline.org>
To: Abhinav Kumar <quic_abhinavk@quicinc.com>
Cc: Jessica Zhang <quic_jesszhan@quicinc.com>,
freedreno@lists.freedesktop.org, Sean Paul <sean@poorly.run>,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
Rob Clark <robdclark@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
linux-arm-msm@vger.kernel.org,
Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
David Airlie <airlied@gmail.com>
Subject: Re: [Freedreno] [PATCH 3/3] drm/msm/dsi: Enable DATABUS_WIDEN for DSI command mode
Date: Fri, 23 Jun 2023 23:33:05 +0200 [thread overview]
Message-ID: <q7ysvtgkhvc3fv4ib65li6hb3p5aw2hfp4ck3d4afuvqxjopzj@mbsg3zr3pint> (raw)
In-Reply-To: <117d21da-aa44-9439-5d5b-9a9144b53979@quicinc.com>
On 2023-06-23 13:34:06, Abhinav Kumar wrote:
>
>
> On 6/23/2023 1:14 PM, Marijn Suijten wrote:
> > On 2023-06-23 10:29:51, Abhinav Kumar wrote:
> > <snip>
> >> The concept is quite simple
> >>
> >> one pixel per clock for uncompresssed without widebubus
> >>
> >> 2 pixels per clock for uncompressed with widebus (only enabled for DP
> >> not DSI)
> >>
> >> 3 bytes worth of data for compressed without widebus
> >>
> >> 6 bytes worth of data for compressed with widebus
> >>
> >> When compression happens, we cannot quantify with pixels as the boundary
> >> is not defined with respect to bytes.
> >>
> >> You brought up uncompressed in your below comment so I assumed your
> >> question of /2 was about uncompressed too.
> >
> > No clue where things are going wrong, but you either avoid or
> > misunderstand the question.
> >
> > (Talking exclusively about compressed data here!)
> >
> > pclk is determined based on the number of bytes.
> >
> > When widebus is enabled, we transfer twice as many bytes per pclk cycle.
> >
> > Can pclk be reduced by a factor two, as that should still be enough to
> > transfer the same amount of bytes when widebus is enabled?
> >
>
> I dont know where the misunderstanding is too.
>
> I already did answer that pclk can be /2 for uncompressed.
Except that my question is about compressed.
> But for compressed it will be divided by the compression ration.
The question here is "why exactly"? I am looking for the argument that
justifies pclk being twice as high for the number of bytes we need to
send.
Is that answer: pclk is not only used for the bus between DPU and DSI?
If the answer to that question is yes, then I'd ask what the advantage
is of widebus.
<snip>
Let's leave the rest for what it is.
- Marijn
next prev parent reply other threads:[~2023-06-23 21:33 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-14 1:57 [PATCH 0/3] Add support for databus widen mode Jessica Zhang
2023-06-14 1:57 ` [PATCH 1/3] drm/msm/dpu: Add DPU_INTF_DATABUS_WIDEN feature flag for DPU >= 5.0 Jessica Zhang
2023-06-14 7:50 ` Dmitry Baryshkov
2023-06-14 11:42 ` Marijn Suijten
2023-06-14 12:01 ` Dmitry Baryshkov
2023-06-14 12:23 ` Marijn Suijten
2023-06-14 19:35 ` Abhinav Kumar
2023-06-14 19:54 ` Abhinav Kumar
2023-06-14 20:39 ` [Freedreno] " Abhinav Kumar
2023-06-14 20:43 ` Dmitry Baryshkov
2023-06-16 21:10 ` Abhinav Kumar
2023-06-17 0:37 ` Dmitry Baryshkov
2023-06-20 21:37 ` Jessica Zhang
2023-06-20 22:11 ` Dmitry Baryshkov
2023-06-20 23:37 ` Jessica Zhang
2023-06-14 21:41 ` Marijn Suijten
2023-06-16 21:13 ` Abhinav Kumar
2023-06-16 21:58 ` Marijn Suijten
2023-06-14 22:49 ` Marijn Suijten
2023-06-16 21:06 ` Abhinav Kumar
2023-06-16 22:00 ` Marijn Suijten
2023-06-14 1:57 ` [PATCH 2/3] drm/msm/dpu: Set DATABUS_WIDEN on command mode encoders Jessica Zhang
2023-06-14 7:56 ` Dmitry Baryshkov
2023-06-16 21:18 ` Abhinav Kumar
2023-06-16 21:54 ` Marijn Suijten
2023-06-17 0:35 ` Dmitry Baryshkov
2023-06-20 21:38 ` Jessica Zhang
2023-06-20 22:10 ` Dmitry Baryshkov
2023-06-21 15:17 ` Marijn Suijten
2023-06-21 16:36 ` Dmitry Baryshkov
2023-06-21 19:00 ` Marijn Suijten
2023-06-21 23:01 ` Abhinav Kumar
2023-06-21 23:46 ` Dmitry Baryshkov
2023-06-22 22:37 ` Abhinav Kumar
2023-06-22 23:14 ` Dmitry Baryshkov
2023-06-22 23:37 ` [Freedreno] " Abhinav Kumar
2023-06-29 17:26 ` Abhinav Kumar
2023-06-29 17:37 ` Jessica Zhang
2023-06-14 1:57 ` [PATCH 3/3] drm/msm/dsi: Enable DATABUS_WIDEN for DSI command mode Jessica Zhang
2023-06-14 7:49 ` Dmitry Baryshkov
2023-06-14 10:03 ` Marijn Suijten
2023-06-22 23:04 ` Abhinav Kumar
2023-06-23 7:02 ` Marijn Suijten
2023-06-16 21:23 ` Abhinav Kumar
2023-06-14 9:56 ` Marijn Suijten
2023-06-23 0:01 ` [Freedreno] " Abhinav Kumar
2023-06-23 0:41 ` Dmitry Baryshkov
2023-06-23 7:19 ` Marijn Suijten
2023-06-23 17:29 ` Abhinav Kumar
2023-06-23 20:14 ` Marijn Suijten
2023-06-23 20:34 ` Abhinav Kumar
2023-06-23 21:33 ` Marijn Suijten [this message]
2023-06-23 21:47 ` Abhinav Kumar
2023-06-14 10:09 ` [PATCH 0/3] Add support for databus widen mode Marijn Suijten
2023-06-16 11:30 ` Dmitry Baryshkov
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