Re: [PATCH 1/3] dt-bindings: display/ti: Add optional property to set memory bandwidth limit

[Peter Ujfalusi <peter.ujfalusi@ti.com>]

Rob,

On 10/27/2017 05:27 AM, Rob Herring wrote:
> On Fri, Oct 20, 2017 at 04:12:56PM +0300, Peter Ujfalusi wrote:
>> max-memory-bandwidth can be used to specify the maximum bandwidth dispc
>> can use when reading display data from main memory.
>>
>> In some SoC (am437x for example) we have memory bandwidth limitation
>> which causes underflow in the display subsystem.
>>
>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
>> ---
>>  Documentation/devicetree/bindings/display/ti/ti,dra7-dss.txt  | 5 +++++
>>  Documentation/devicetree/bindings/display/ti/ti,omap2-dss.txt | 4 ++++
>>  Documentation/devicetree/bindings/display/ti/ti,omap3-dss.txt | 4 ++++
>>  Documentation/devicetree/bindings/display/ti/ti,omap4-dss.txt | 4 ++++
>>  Documentation/devicetree/bindings/display/ti/ti,omap5-dss.txt | 4 ++++
>>  5 files changed, 21 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/display/ti/ti,dra7-dss.txt b/Documentation/devicetree/bindings/display/ti/ti,dra7-dss.txt
>> index c30f9ec189ed..91279f1060fe 100644
>> --- a/Documentation/devicetree/bindings/display/ti/ti,dra7-dss.txt
>> +++ b/Documentation/devicetree/bindings/display/ti/ti,dra7-dss.txt
>> @@ -47,6 +47,11 @@ Required properties:
>>  - clocks: handle to fclk
>>  - clock-names: "fck"
>>  
>> +Optional properties:
>> +- max-memory-bandwidth: Input memory (from main memory to dispc) bandwidth limit
>> +			in bytes per second
> 
> Can we move this to a common location since we already have the same 
> prop for ARM pl11x.

This is why I used the same string for ti,* as I saw that pl11x have it
documented (the driver is not supporting it afaik, it is in the TODO).

I don't see any generic documentation for Display, not sure what would be the
best place for things like this.

While it is true that memory bandwidth limit can be a generic property, but it
might (not sure about it) can apply to different interfaces among different
vendors. The device specific documentation should either way need to mention
that it supports memory bandwidth limitation or not.

-- 
Péter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
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