From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4C6FC2B9F8 for ; Tue, 25 May 2021 08:03:27 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 90B52613F9 for ; Tue, 25 May 2021 08:03:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 90B52613F9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 924E189135; Tue, 25 May 2021 08:03:19 +0000 (UTC) Received: from m43-7.mailgun.net (m43-7.mailgun.net [69.72.43.7]) by gabe.freedesktop.org (Postfix) with ESMTPS id D8C596E9BC for ; Tue, 25 May 2021 08:03:16 +0000 (UTC) DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1621929796; h=Message-ID: References: In-Reply-To: Subject: Cc: To: From: Date: Content-Transfer-Encoding: Content-Type: MIME-Version: Sender; bh=/kEnPjhJjqrbSkYAOsYKI4/+SBWF5gUGEh00EhIqOGA=; b=sG9K/C3Wa3O5bRKu/x0b1dmhPJ3jRPQvVRcKTr4nODxUDSLYv3YEal/akOaRo4TXmr8npzNy OeGXjBBzfnZYvGwZ3VcgmW+wpmK+u+4Os9XmUoTvNEVsu7SYzbnHwF8e2dSH7iRaZMid4+vY lIzwv+jfS0oBRcmg8HVUeGRiVas= X-Mailgun-Sending-Ip: 69.72.43.7 X-Mailgun-Sid: WyJkOTU5ZSIsICJkcmktZGV2ZWxAbGlzdHMuZnJlZWRlc2t0b3Aub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n05.prod.us-west-2.postgun.com with SMTP id 60acaf3fc229adfeff7afadf (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Tue, 25 May 2021 08:03:11 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 2B6F7C4338A; Tue, 25 May 2021 08:03:11 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: rajeevny) by smtp.codeaurora.org (Postfix) with ESMTPSA id 82687C433D3; Tue, 25 May 2021 08:03:08 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Tue, 25 May 2021 13:33:08 +0530 From: rajeevny@codeaurora.org To: Doug Anderson Subject: Re: [v3 1/2] dt-bindings: backlight: add DisplayPort aux backlight In-Reply-To: References: <1619416756-3533-1-git-send-email-rajeevny@codeaurora.org> <1619416756-3533-2-git-send-email-rajeevny@codeaurora.org> <20210429180435.GA1385465@robh.at.kernel.org> <78c4bd291bd4a17ae2a1d02d0217de43@codeaurora.org> Message-ID: <3fbad05fd1e944ed3e0d493d1f5470e6@codeaurora.org> X-Sender: rajeevny@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mkrishn@codeaurora.org, "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , linux-arm-msm , LKML , dri-devel , Andrzej Hajda , Sean Paul , Abhinav Kumar , Kalyan Thota , "Kristian H. Kristensen" , freedreno , "Lankhorst, Maarten" , Laurent Pinchart Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi, On 18-05-2021 01:51, Doug Anderson wrote: > Hi, > > On Tue, May 11, 2021 at 4:17 PM Doug Anderson > wrote: >> >> Hi, >> >> On Tue, May 11, 2021 at 11:12 AM wrote: >> > >> > On 01-05-2021 03:08, Doug Anderson wrote: >> > > Hi, >> > > >> > > On Fri, Apr 30, 2021 at 8:10 AM wrote: >> > >> >> > >> On 30-04-2021 02:33, Doug Anderson wrote: >> > >> > Hi, >> > >> > >> > >> > On Thu, Apr 29, 2021 at 11:04 AM Rob Herring wrote: >> > >> >> >> > >> >> On Mon, Apr 26, 2021 at 11:29:15AM +0530, Rajeev Nandan wrote: >> > >> >> > Add bindings for DisplayPort aux backlight driver. >> > >> >> > >> > >> >> > Changes in v2: >> > >> >> > - New >> > >> >> > >> > >> >> > Signed-off-by: Rajeev Nandan >> > >> >> > --- >> > >> >> > .../bindings/leds/backlight/dp-aux-backlight.yaml | 49 ++++++++++++++++++++++ >> > >> >> > 1 file changed, 49 insertions(+) >> > >> >> > create mode 100644 Documentation/devicetree/bindings/leds/backlight/dp-aux-backlight.yaml >> > >> >> > >> > >> >> > diff --git a/Documentation/devicetree/bindings/leds/backlight/dp-aux-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/dp-aux-backlight.yaml >> > >> >> > new file mode 100644 >> > >> >> > index 00000000..0fa8bf0 >> > >> >> > --- /dev/null >> > >> >> > +++ b/Documentation/devicetree/bindings/leds/backlight/dp-aux-backlight.yaml >> > >> >> > @@ -0,0 +1,49 @@ >> > >> >> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) >> > >> >> > +%YAML 1.2 >> > >> >> > +--- >> > >> >> > +$id: http://devicetree.org/schemas/leds/backlight/dp-aux-backlight.yaml# >> > >> >> > +$schema: http://devicetree.org/meta-schemas/core.yaml# >> > >> >> > + >> > >> >> > +title: DisplayPort aux backlight driver bindings >> > >> >> > + >> > >> >> > +maintainers: >> > >> >> > + - Rajeev Nandan >> > >> >> > + >> > >> >> > +description: >> > >> >> > + Backlight driver to control the brightness over DisplayPort aux channel. >> > >> >> > + >> > >> >> > +allOf: >> > >> >> > + - $ref: common.yaml# >> > >> >> > + >> > >> >> > +properties: >> > >> >> > + compatible: >> > >> >> > + const: dp-aux-backlight >> > >> >> > + >> > >> >> > + ddc-i2c-bus: >> > >> >> > + $ref: /schemas/types.yaml#/definitions/phandle >> > >> >> > + description: >> > >> >> > + A phandle to the system I2C controller connected to the DDC bus used >> > >> >> > + for the DisplayPort AUX channel. >> > >> >> > + >> > >> >> > + enable-gpios: >> > >> >> > + maxItems: 1 >> > >> >> > + description: GPIO specifier for backlight enable pin. >> > >> >> > + >> > >> >> > + max-brightness: true >> > >> >> > + >> > >> >> > +required: >> > >> >> > + - compatible >> > >> >> > + - ddc-i2c-bus >> > >> >> > + >> > >> >> > +additionalProperties: false >> > >> >> > + >> > >> >> > +examples: >> > >> >> > + - | >> > >> >> > + backlight { >> > >> >> > + compatible = "dp-aux-backlight"; >> > >> >> > + ddc-i2c-bus = <&sn65dsi86_bridge>; >> > >> >> > + enable-gpios = <&tlmm 12 GPIO_ACTIVE_HIGH>; >> > >> >> >> > >> >> So the DDC bus is connected to a backlight and also a panel? This >> > >> >> binding is not reflecting the h/w, but rather what you want for some >> > >> >> driver. >> > >> >> >> > >> >> There's only one thing here and that's an eDP panel which supports >> > >> >> backlight control via DP aux channel. You can figure all that out from >> > >> >> the panel's compatible and/or reading the EDID. >> > >> >> >> > >> >> You might also be interested in this thread: >> > >> >> >> > >> >> https://lore.kernel.org/lkml/YIKsDtjcIHGNvW0u@orome.fritz.box/ >> > >> > >> > >> > I think Rajeev needs to rework everything anyway as per: >> > >> > >> > >> > https://lore.kernel.org/r/87zgxl5qar.fsf@intel.com >> > >> > >> > >> > ...but you're right that it makes sense not to model the backlight as >> > >> > a separate node in the device tree. The panel driver can handle >> > >> > setting up the backlight. >> > >> > >> > >> > -Doug >> > >> >> > >> It was not a good idea to create a separate backlight driver and use >> > >> ddc-i2c-bus to get access to DP aux. I am working to move the code >> > >> to the panel driver and to utilize the new DRM helper functions >> > >> (drm_edp_backlight_*) Lyude has added [1]. >> > >> >> > >> To use these helper functions, the panel driver should have access to >> > >> the >> > >> "struct drm_dp_aux *". The simple-panel has a "ddc-i2c-bus" property >> > >> to give the panel access to the DDC bus and is currently being used to >> > >> get the EDID from the panel. Can I use the same ddc bus i2c_adapter to >> > >> get >> > >> the "struct drm_dp_aux *"? >> > >> >> > >> As per the suggestion [2], I get the "struct drm_dp_aux *" from the >> > >> i2c_adapter of ddc bus (maybe I didn't understand the suggestion >> > >> correctly), >> > >> and, it turned out, the way I have implemented is not the right way >> > >> [3]. >> > >> So, I am afraid to use the same method in the panel driver. >> > >> >> > >> >> > >> [1] https://lore.kernel.org/dri-devel/871rb5bcf9.fsf@intel.com/ >> > >> [2] https://www.spinics.net/lists/dri-devel/msg295429.html >> > >> [3] >> > >> https://lore.kernel.org/dri-devel/20210426111116.4lc3ekxjugjr3oho@maple.lan/ >> > > >> > > So it's definitely up to maintainers, not me. ...but I guess I would >> > > have expected something like a new property called "ddc-aux-bus". Then >> > > you'd have to create a new API call called something like >> > > "of_find_ddc_aux_adapter_by_node()" that would allow you to find it. >> > > >> > >> > To implement the first suggestion, I can think of the following way >> > to get the "struct drm_dp_aux" in the panel_simple_probe function: >> > >> > - Create a new panel-simple DT property "ddc-aux-bus", a phandle to the >> > platform device that implements the AUX channel. >> > >> > - Create a global list of drm_dp_aux in drm_dp_helper.c. Initialize list >> > head >> > in drm_dp_aux_init(), add the drm_dp_aux onto the list in >> > drm_dp_aux_register(). >> > Similarly, remove the drm_dp_aux from list in drm_dp_aux_unregister(). >> > >> > - Create a new function of_drm_find_dp_aux_by_node() to get the expected >> > drm_dp_aux from this global list. >> > >> > Please let me know your views on this implementation. >> >> BTW: a bunch of discussion today on IRC: >> >> https://people.freedesktop.org/~cbrill/dri-log/?channel=dri-devel&highlight_names=&date=2021-05-11&show_html=true > > To finish adding breadcrumbs to those playing at home, v7 of my patch > series should get the AUX channel to the panel device: > > https://lore.kernel.org/r/20210517200907.1459182-1-dianders@chromium.org/ > > Assuming that people don't hate that solution it may be a good things > for you to build your patches atop. :-) > > -Doug Thank you, for all your suggestions. I have posted the new patch series (v4) on top of the above series. Please check: https://lore.kernel.org/dri-devel/1621927831-29471-1-git-send-email-rajeevny@codeaurora.org/ Thanks, Rajeev