Hi Archit,

On Friday 22 Apr 2016 11:10:18 Archit Taneja wrote:

On 04/22/2016 04:02 AM, Laurent Pinchart wrote:

quoted

On Wednesday 09 Mar 2016 16:27:18 Archit Taneja wrote:

quoted

Add description of ADV7533. Add the required and optional properties that
are specific to it.

Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: Rob Herring <redacted>

Signed-off-by: Archit Taneja <redacted>
---

.../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]

quoted

quoted

+- 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

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