From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laurent Pinchart Subject: Re: [PATCH v3 7/7] dt-bindings: drm/bridge: Update bindings for ADV7533 Date: Mon, 16 May 2016 15:01:35 +0300 Message-ID: <1987165.vo5BTWVL5e@avalon> References: <1441625800-1858-1-git-send-email-architt@codeaurora.org> <1992414.kkmfQUJ8oO@avalon> <5719B942.8070907@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <5719B942.8070907-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Archit Taneja Cc: dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, airlied-cv59FeDIM0c@public.gmane.org, daniel-/w4YWyX8dFk@public.gmane.org, treding-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, linux-arm-msm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, srinivas.kandagatla-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, andy.green-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, lars-Qo5EllUWu/uELgA04lAiVw@public.gmane.org, xinliang.liu-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, amit.kucheria-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, robdclark-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Rob Herring List-Id: linux-arm-msm@vger.kernel.org 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-u79uwXL29TY76Z2rM5mHXA@public.gmane.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 ? -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html