From mboxrd@z Thu Jan 1 00:00:00 1970 From: Archit Taneja Subject: Re: [PATCH v3 7/7] dt-bindings: drm/bridge: Update bindings for ADV7533 Date: Tue, 17 May 2016 09:13:25 +0530 Message-ID: <573A935D.7010301@codeaurora.org> References: <1441625800-1858-1-git-send-email-architt@codeaurora.org> <1992414.kkmfQUJ8oO@avalon> <5719B942.8070907@codeaurora.org> <1987165.vo5BTWVL5e@avalon> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1987165.vo5BTWVL5e@avalon> Sender: linux-arm-msm-owner@vger.kernel.org To: Laurent Pinchart , xinliang.liu@linaro.orgXinliang Liu Cc: dri-devel@lists.freedesktop.org, airlied@linux.ie, daniel@ffwll.ch, treding@nvidia.com, linux-arm-msm@vger.kernel.org, srinivas.kandagatla@linaro.org, lars@metafoo.de, amit.kucheria@linaro.org, robdclark@gmail.com, devicetree@vger.kernel.org, Rob Herring List-Id: devicetree@vger.kernel.org On 05/16/2016 05:31 PM, Laurent Pinchart wrote: > Hi Archit, > > On Friday 22 Apr 2016 11:10:18 Archit Taneja wrote: >> On 04/22/2016 04:02 AM, Laurent Pinchart wrote: >>> On Wednesday 09 Mar 2016 16:27:18 Archit Taneja wrote: >>>> Add description of ADV7533. Add the required and optional properties that >>>> are specific to it. >>>> >>>> Cc: devicetree@vger.kernel.org >>>> Cc: Rob Herring >>>> >>>> Signed-off-by: Archit Taneja >>>> --- >>>> >>>> .../bindings/display/bridge/adi,adv7511.txt | 25 ++++++++++++----- >>>> 1 file changed, 20 insertions(+), 5 deletions(-) >>>> >>>> diff --git >>>> a/Documentation/devicetree/bindings/display/bridge/adi,adv7511.txt >>>> b/Documentation/devicetree/bindings/display/bridge/adi,adv7511.txt index >>>> 96c25ee..420da5a 100644 >>>> --- a/Documentation/devicetree/bindings/display/bridge/adi,adv7511.txt >>>> +++ b/Documentation/devicetree/bindings/display/bridge/adi,adv7511.txt > > [snip] > >>>> +- adi,disable-timing-generator: Only for ADV7533. Disables the internal >>>> timing >>>> + generator. The chip will rely on the sync signals in the DSI data >>>> lanes, >>>> + rather than generate its own timings for HDMI output. >>> >>> Isn't that something that should be selectable at runtime ? >> >> The timing generator can be enabled/disabled at runtime. Although, we >> don't have a way to tell the driver whether we want to keep it enabled >> or not. >> >> It's a hardware feature that works well on most platforms, but not on >> all. In particular, it works well on DB410c, but causes issues with >> the Hikey 96 board. The DSI host on Hikey has different clock sources >> that generate the display controller's pixel clock and DSI byte clock, >> whereas the Qualcomm SoC uses the same source. My guess is that the >> ADV7533's timing generator doesn't like it when the pixel data and >> clock are out of phase or something. >> >> Since it is a hardware feature which needs tweaking, I thought it >> qualified as a DT property. > > The fact that a hardware generator is present is certainly describes the > hardware, but I'm not sure whether to enable it or not also qualifies as a > hardware feature. > > Are there use cases for using the timing generator conditionally on a given > board ? As you implement support for disabling it, I assume it's not > mandatory. What feature(s) do we lose if we keep it disabled ? > The spec says it's recommended to use the internal timing generator. In the case of db410c, I observe an unstable output/flicker for certain modes if I don't enable it. In the case of hikey platform, it's the other way round. Xinliang, could you describe the problems you face when the timing generator is enabled? Thanks, Archit -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation