From: Laurent Pinchart <laurent.pinchart@ideasonboard.com> To: Doug Anderson <dianders@chromium.org> Cc: Kieran Bingham <kieran.bingham@ideasonboard.com>, Jernej Skrabec <jernej.skrabec@siol.net>, Jonas Karlman <jonas@kwiboo.se>, Neil Armstrong <narmstrong@baylibre.com>, dri-devel <dri-devel@lists.freedesktop.org>, Stephen Boyd <swboyd@chromium.org>, Linux-Renesas <linux-renesas-soc@vger.kernel.org>, Andrzej Hajda <a.hajda@samsung.com> Subject: Re: [RFC PATCH 10/11] drm/bridge: ti-sn65dsi86: Support DisplayPort (non-eDP) mode Date: Fri, 4 Mar 2022 17:49:23 +0200 [thread overview] Message-ID: <YiI1A+dtLXMQzkVf@pendragon.ideasonboard.com> (raw) In-Reply-To: <CAD=FV=WSHpu3Ub=0Gbq01o_s-SsUa_Q6uC7Z3PaxFL00eeJbdw@mail.gmail.com> On Wed, Feb 23, 2022 at 10:20:18AM -0800, Doug Anderson wrote: > On Wed, Feb 23, 2022 at 10:05 AM Kieran Bingham wrote: > > > > > > > + /* For DisplayPort, disable scrambling mode. */ > > > > > + if (pdata->bridge.type == DRM_MODE_CONNECTOR_DisplayPort) > > > > > + regmap_update_bits(pdata->regmap, SN_TRAINING_SETTING_REG, > > > > > + SCRAMBLE_DISABLE, SCRAMBLE_DISABLE); > > > > > > > > I'm assuming that this is the important part of your patch? Would be > > > > sorta nice to include the "why" in your comment. Why do you want to > > > > disable scrambling mode for DP but not for eDP? Maybe you care about > > > > compatibility but not EMI if you're hooking up to random DP things? > > > > > > I'll investigate and include proper documentation in v2 (or drop the > > > change altogether if it's not required). > > > > And indeed, this part is important. If I drop this hunk - then I get no > > display output. > > > > I'm afraid I don't (yet) know the reasons 'why' to extend the comment, > > beyond "Scrambling is not supported for DP". > > > > If anyone already does, please feel free to provide the text, and I'll > > include it in the next revision, or I'll try to do some more digging > > into this part. > > I don't know _tons_ about it, but I later learned that the "alternate" > scrambler is used for eDP and the normal scrambler is used for DP. I > don't have any background about why they are different other than what > looks to be intentionally making the two things incompatible. I think it was done for DRM purpose, to prevent signals meant for a panel to be connected to a device that could capture video from a DP source. > ...so I guess that would make it pretty clear why you can't use the > alternate scrambler for DP. I haven't personally done the research to > know if you can be officially DP compliant with the scrambler > disabled. I also don't know why the ti-sn65dsi86 makes it so difficult > to switch to the standard scrambler or if it works at all... ;-) -- Regards, Laurent Pinchart
WARNING: multiple messages have this Message-ID (diff)
From: Laurent Pinchart <laurent.pinchart@ideasonboard.com> To: Doug Anderson <dianders@chromium.org> Cc: Jernej Skrabec <jernej.skrabec@siol.net>, Neil Armstrong <narmstrong@baylibre.com>, Jonas Karlman <jonas@kwiboo.se>, Kieran Bingham <kieran.bingham@ideasonboard.com>, dri-devel <dri-devel@lists.freedesktop.org>, Stephen Boyd <swboyd@chromium.org>, Linux-Renesas <linux-renesas-soc@vger.kernel.org>, Andrzej Hajda <a.hajda@samsung.com> Subject: Re: [RFC PATCH 10/11] drm/bridge: ti-sn65dsi86: Support DisplayPort (non-eDP) mode Date: Fri, 4 Mar 2022 17:49:23 +0200 [thread overview] Message-ID: <YiI1A+dtLXMQzkVf@pendragon.ideasonboard.com> (raw) In-Reply-To: <CAD=FV=WSHpu3Ub=0Gbq01o_s-SsUa_Q6uC7Z3PaxFL00eeJbdw@mail.gmail.com> On Wed, Feb 23, 2022 at 10:20:18AM -0800, Doug Anderson wrote: > On Wed, Feb 23, 2022 at 10:05 AM Kieran Bingham wrote: > > > > > > > + /* For DisplayPort, disable scrambling mode. */ > > > > > + if (pdata->bridge.type == DRM_MODE_CONNECTOR_DisplayPort) > > > > > + regmap_update_bits(pdata->regmap, SN_TRAINING_SETTING_REG, > > > > > + SCRAMBLE_DISABLE, SCRAMBLE_DISABLE); > > > > > > > > I'm assuming that this is the important part of your patch? Would be > > > > sorta nice to include the "why" in your comment. Why do you want to > > > > disable scrambling mode for DP but not for eDP? Maybe you care about > > > > compatibility but not EMI if you're hooking up to random DP things? > > > > > > I'll investigate and include proper documentation in v2 (or drop the > > > change altogether if it's not required). > > > > And indeed, this part is important. If I drop this hunk - then I get no > > display output. > > > > I'm afraid I don't (yet) know the reasons 'why' to extend the comment, > > beyond "Scrambling is not supported for DP". > > > > If anyone already does, please feel free to provide the text, and I'll > > include it in the next revision, or I'll try to do some more digging > > into this part. > > I don't know _tons_ about it, but I later learned that the "alternate" > scrambler is used for eDP and the normal scrambler is used for DP. I > don't have any background about why they are different other than what > looks to be intentionally making the two things incompatible. I think it was done for DRM purpose, to prevent signals meant for a panel to be connected to a device that could capture video from a DP source. > ...so I guess that would make it pretty clear why you can't use the > alternate scrambler for DP. I haven't personally done the research to > know if you can be officially DP compliant with the scrambler > disabled. I also don't know why the ti-sn65dsi86 makes it so difficult > to switch to the standard scrambler or if it works at all... ;-) -- Regards, Laurent Pinchart
next prev parent reply other threads:[~2022-03-04 15:49 UTC|newest] Thread overview: 112+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-03-22 3:01 [RFC PATCH 00/11] drm/bridge: ti-sn65dsi86: Support DisplayPort mode Laurent Pinchart 2021-03-22 3:01 ` Laurent Pinchart 2021-03-22 3:01 ` [RFC PATCH 01/11] dt-bindings: drm/bridge: ti-sn65dsi8: Make enable GPIO optional Laurent Pinchart 2021-03-22 3:01 ` Laurent Pinchart 2021-03-22 10:29 ` Jagan Teki 2021-03-22 10:29 ` Jagan Teki 2021-03-23 7:10 ` Stephen Boyd 2021-03-23 7:10 ` Stephen Boyd 2021-03-23 21:08 ` Doug Anderson 2021-03-23 21:08 ` Doug Anderson 2021-03-27 16:42 ` Rob Herring 2021-03-27 16:42 ` Rob Herring 2021-03-22 3:01 ` [RFC PATCH 02/11] drm/bridge: ti-sn65dsi86: " Laurent Pinchart 2021-03-22 3:01 ` Laurent Pinchart 2021-03-22 10:29 ` Jagan Teki 2021-03-22 10:29 ` Jagan Teki 2021-03-23 7:10 ` Stephen Boyd 2021-03-23 7:10 ` Stephen Boyd 2021-03-23 21:08 ` Doug Anderson 2021-03-23 21:08 ` Doug Anderson 2021-03-22 3:01 ` [RFC PATCH 03/11] drm/bridge: ti-sn65dsi86: Unregister AUX adapter in remove() Laurent Pinchart 2021-03-22 3:01 ` Laurent Pinchart 2021-03-23 7:10 ` Stephen Boyd 2021-03-23 7:10 ` Stephen Boyd 2021-03-23 21:08 ` Doug Anderson 2021-03-23 21:08 ` Doug Anderson 2021-03-23 21:41 ` Laurent Pinchart 2021-03-23 21:41 ` Laurent Pinchart 2021-03-23 22:55 ` Doug Anderson 2021-03-23 22:55 ` Doug Anderson 2021-03-23 23:02 ` Laurent Pinchart 2021-03-23 23:02 ` Laurent Pinchart 2021-03-26 0:43 ` Doug Anderson 2021-03-26 0:43 ` Doug Anderson 2021-03-26 1:01 ` Laurent Pinchart 2021-03-26 1:01 ` Laurent Pinchart 2021-03-22 3:01 ` [RFC PATCH 04/11] drm/bridge: ti-sn65dsi86: Use bitmask to store valid rates Laurent Pinchart 2021-03-22 3:01 ` Laurent Pinchart 2021-03-23 7:11 ` Stephen Boyd 2021-03-23 7:11 ` Stephen Boyd 2021-03-23 21:08 ` Doug Anderson 2021-03-23 21:08 ` Doug Anderson 2021-03-23 21:45 ` Laurent Pinchart 2021-03-23 21:45 ` Laurent Pinchart 2021-03-23 22:45 ` Doug Anderson 2021-03-23 22:45 ` Doug Anderson 2021-03-24 8:47 ` Geert Uytterhoeven 2021-03-24 8:47 ` Geert Uytterhoeven 2021-03-22 3:01 ` [RFC PATCH 05/11] drm/bridge: ti-sn65dsi86: Wrap panel with panel-bridge Laurent Pinchart 2021-03-22 3:01 ` Laurent Pinchart 2021-03-22 10:19 ` Jagan Teki 2021-03-22 10:19 ` Jagan Teki 2021-03-23 7:14 ` Stephen Boyd 2021-03-23 7:14 ` Stephen Boyd 2021-03-23 21:50 ` Laurent Pinchart 2021-03-23 21:50 ` Laurent Pinchart 2021-03-24 22:44 ` Doug Anderson 2021-03-24 22:44 ` Doug Anderson 2021-03-26 1:06 ` Laurent Pinchart 2021-03-26 1:06 ` Laurent Pinchart 2021-03-22 3:01 ` [RFC PATCH 06/11] drm/bridge: ti-sn65dsi86: Group code in sections Laurent Pinchart 2021-03-22 3:01 ` Laurent Pinchart 2021-03-23 7:14 ` Stephen Boyd 2021-03-23 7:14 ` Stephen Boyd 2021-03-24 22:44 ` Doug Anderson 2021-03-24 22:44 ` Doug Anderson 2021-03-22 3:01 ` [RFC PATCH 07/11] drm/bridge: ti-sn65dsi86: Split connector creation to a function Laurent Pinchart 2021-03-22 3:01 ` Laurent Pinchart 2021-03-23 7:15 ` Stephen Boyd 2021-03-23 7:15 ` Stephen Boyd 2021-03-24 22:44 ` Doug Anderson 2021-03-24 22:44 ` Doug Anderson 2021-03-22 3:01 ` [RFC PATCH 08/11] drm/bridge: ti-sn65dsi86: Implement bridge connector operations Laurent Pinchart 2021-03-22 3:01 ` Laurent Pinchart 2021-03-23 7:15 ` Stephen Boyd 2021-03-23 7:15 ` Stephen Boyd 2021-03-24 22:46 ` Doug Anderson 2021-03-24 22:46 ` Doug Anderson 2021-03-26 1:40 ` Laurent Pinchart 2021-03-26 1:40 ` Laurent Pinchart 2021-03-22 3:01 ` [RFC PATCH 09/11] drm/bridge: ti-sn65dsi86: Make connector creation optional Laurent Pinchart 2021-03-22 3:01 ` Laurent Pinchart 2021-03-22 3:01 ` [RFC PATCH 10/11] drm/bridge: ti-sn65dsi86: Support DisplayPort (non-eDP) mode Laurent Pinchart 2021-03-22 3:01 ` Laurent Pinchart 2021-03-24 22:47 ` Doug Anderson 2021-03-24 22:47 ` Doug Anderson 2021-06-23 13:59 ` Laurent Pinchart 2021-06-23 13:59 ` Laurent Pinchart 2022-02-23 18:04 ` Kieran Bingham 2022-02-23 18:04 ` Kieran Bingham 2022-02-23 18:20 ` Doug Anderson 2022-02-23 18:20 ` Doug Anderson 2022-03-04 15:49 ` Laurent Pinchart [this message] 2022-03-04 15:49 ` Laurent Pinchart 2021-03-22 3:01 ` [RFC PATCH 11/11] drm/bridge: ti-sn65dsi86: Support hotplug detection Laurent Pinchart 2021-03-22 3:01 ` Laurent Pinchart 2021-03-23 7:21 ` Stephen Boyd 2021-03-23 7:21 ` Stephen Boyd 2021-03-24 22:47 ` Doug Anderson 2021-03-24 22:47 ` Doug Anderson 2021-06-23 23:25 ` Laurent Pinchart 2021-06-23 23:25 ` Laurent Pinchart 2021-06-23 23:51 ` Doug Anderson 2021-06-23 23:51 ` Doug Anderson 2022-02-23 17:43 ` Kieran Bingham 2022-02-23 17:43 ` Kieran Bingham 2022-02-23 18:25 ` Doug Anderson 2022-02-23 18:25 ` Doug Anderson 2022-03-04 15:45 ` Kieran Bingham 2022-03-04 15:45 ` Kieran Bingham 2022-03-04 16:30 ` Doug Anderson 2022-03-04 16:30 ` Doug Anderson
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