From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yakir Yang Subject: Re: [PATCH v3 06/14] Documentation: drm/bridge: add document for analogix_dp Date: Tue, 25 Aug 2015 21:48:01 +0800 Message-ID: <55DC7211.9080601@rock-chips.com> References: <1439995728-18046-1-git-send-email-ykk@rock-chips.com> <1439995834-18363-1-git-send-email-ykk@rock-chips.com> <20150825091534.GB14034@ulmo.nvidia.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1652952043==" Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Rob Herring , Thierry Reding Cc: Sean Paul , dri-devel , Andrzej Hajda , Gustavo Padovan , "linux-samsung-soc@vger.kernel.org" , Vincent Palatin , Kishon Vijay Abraham I , linux-rockchip@lists.infradead.org, Russell King , "devicetree@vger.kernel.org" , Pawel Moll , Ian Campbell , Doug Anderson , Ajay kumar , Rob Herring , "linux-arm-kernel@lists.infradead.org" , Fabio Estevam , Jingoo Han , "linux-kernel@vger.kernel.org" , Kyungmin Park List-Id: devicetree@vger.kernel.org This is a multi-part message in MIME format. --===============1652952043== Content-Type: multipart/alternative; boundary="------------020802030208020009020809" This is a multi-part message in MIME format. --------------020802030208020009020809 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable Hi Thierry & Rob, =E5=9C=A8 2015/8/25 21:27, Rob Herring =E5=86=99=E9=81=93: > On Tue, Aug 25, 2015 at 4:15 AM, Thierry Reding wr= ote: >> On Sun, Aug 23, 2015 at 06:23:14PM -0500, Rob Herring wrote: >>> On Wed, Aug 19, 2015 at 9:50 AM, Yakir Yang wrot= e: >> [...] >>>> + -analogix,link-rate: >>>> + max link rate supported by the eDP controller. >>>> + LINK_RATE_1_62GBPS =3D 0x6, LINK_RATE_2_70GB= PS =3D 0x0A, >>>> + LINK_RATE_5_40GBPS =3D 0x14 >>> Same here. I'd rather see something like "link-rate-mbps" and use the >>> actual rate. >> There is no need whatsoever to hard-code this in DT. (e)DP provides th= e >> means to detect what rate the link supports and the specification >> provides guidance on how to select an appropriate one. > Good, even better. I do think we still need keep this DT prop yet. I think drm_dp_help.c could get the "panel" max link-rate and lane-count, but it's not enough, we still need knew the "eDP controller" max link-rat= e and lane-count. Let me show the exact example that happened in my side. When I connect my board to my 2K DP-1.2 TV. Analogix dp driver would get the max link-ra= te from dpcd, and the max link-rate is 5.4Gbps. So if I just set eDP=20 controller link-rate to 5.4Gbps, the DP TV just broken, do not light up normally. This reason why TV broken is the max link-rate which support by RK3288 eD= P controller is 2.7Gbps. Here are the exact words that RK3288 eDP TRM said: *=EF=81=AC=EF=80=A0Compliant with DisplayPortTM Specification, Version 1.= 2. =EF=81=AC=EF=80=A0Compliant with eDPTM Specification, Version 1.3. =EF=81=AC=EF=80=A0HDCP v1.3 amendment for DisplayPortTM Revision 1.0. =EF=81=AC=EF=80=A0Main link containing 4 physical lanes of 2.7/1.62 Gbps/= lane * ** Beside I haven't found there are some registers would indicate the eDP=20 controller max link-rate and lane-count, so this is why I still instance that we=20 need this DT prop to indicata "Max rate controller support". So, I wish you could agree with me on this point. Thanks, - Yakir > Rob > > > --------------020802030208020009020809 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hi Thierry & Rob,

=E5=9C=A8 2015/8/25 21:27, Rob Herring= =E5=86=99=E9=81=93:
On Tue, Aug 25, 2015 at 4:15 AM, Thierry Reding <tre=
ding@nvidia.com> wrote:

On Sun, Aug 23, 2015 at 06:23:14PM -0500, Rob Herr=
ing wrote:

On Wed, Aug 19, 2015 at 9:50 AM, Yakir Yang <ykk=
@rock-chips.com> wrote:

[...]

+       -analogix,link-rate:
+               max link rate supported by the eDP controller.
+                       LINK_RATE_1_62GBPS =3D 0x6, LINK_RATE_2_70GBPS =3D=
 0x0A,
+                       LINK_RATE_5_40GBPS =3D 0x14

Same here. I'd rather see something like "link-rate-mbps" and use the
actual rate.

There is no need whatsoever to hard-code this in DT. (e)DP provides the
means to detect what rate the link supports and the specification
provides guidance on how to select an appropriate one.

Good, even better.

I do think we still need keep this DT prop yet.

I think drm_dp_help.c could get the "panel" max link-rate and lane-count,
but it's not enough, we still need knew the "eDP controller" max link-rate
and lane-count.

Let me show the exact example that happened in my side. When I connect
my board to my 2K DP-1.2 TV. Analogix dp driver would get the max link-rate
from dpcd, and the max link-rate is 5.4Gbps. So if I just set eDP controller link-rate
to 5.4Gbps, the DP TV just broken, do not light up normally.

This reason why TV broken is the max link-rate which support by RK3288 eDP
controller is 2.7Gbps. Here are the exact words that RK3288 eDP TRM said:

=EF=81=AC=EF=80=A0Compliant with DisplayPortTM Specification, Version 1.2.
=EF=81=AC=EF=80=A0Compliant with eDPTM Specification, V= ersion 1.3.
=EF=81=AC=EF=80=A0HDCP v1.3 amendment for DisplayPortTM= Revision 1.0.
=EF=81=AC=EF=80=A0Main link containing 4 physical lanes= of 2.7/1.62 Gbps/lane


Beside I haven't found there are some registers would indicate the eDP controller
max link-rate and lane-count, so this is why I still instance that we need this DT
prop to indicata "Max rate controller support".

So, I wish you could agree with me on this point.


Thanks,
- Yakir

Rob

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