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[PATCH v2 2/2] ARM: dts: da850-lcdk: specify the maximum pixel clock rate for tilcdc

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  [PATCH v2 2/2] ARM: dts: da850-lcdk: specify the maximum pixel clock rate for tilcdc Bartosz Golaszewski <bgolaszewski@baylibre.com> - 2016-11-28 13:20 +0100
    Re: [PATCH v2 2/2] ARM: dts: da850-lcdk: specify the maximum pixel  clock rate for tilcdc Sekhar Nori <nsekhar@ti.com> - 2016-11-29 12:00 +0100
      Re: [PATCH v2 2/2] ARM: dts: da850-lcdk: specify the maximum pixel  clock rate for tilcdc Bartosz Golaszewski <bgolaszewski@baylibre.com> - 2016-11-29 13:00 +0100

#1531255 — [PATCH v2 2/2] ARM: dts: da850-lcdk: specify the maximum pixel clock rate for tilcdc

Due to memory throughput constraints any display mode for which the
pixel clock rate exceeds the recommended value of 37500 KHz must be
filtered out.

Specify the max-pixelclock property for the display node for
da850-lcdk.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 arch/arm/boot/dts/da850-lcdk.dts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/boot/dts/da850-lcdk.dts b/arch/arm/boot/dts/da850-lcdk.dts
index d864f11..1283263 100644
--- a/arch/arm/boot/dts/da850-lcdk.dts
+++ b/arch/arm/boot/dts/da850-lcdk.dts
@@ -285,6 +285,7 @@
 
 &display {
 	status = "okay";
+	max-pixelclock = <37500>;
 };
 
 &display_out {
-- 
2.9.3

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#1532126 — Re: [PATCH v2 2/2] ARM: dts: da850-lcdk: specify the maximum pixel clock rate for tilcdc

On Monday 28 November 2016 05:45 PM, Bartosz Golaszewski wrote:
> Due to memory throughput constraints any display mode for which the
> pixel clock rate exceeds the recommended value of 37500 KHz must be
> filtered out.

I think there might be more reasons than memory throughput constraints
for the reasoning behind 37.5Mhz cap on pixel clock. Why not just refer
to the datasheet section that places this constraint so we know its a
hardware restriction.

> 
> Specify the max-pixelclock property for the display node for
> da850-lcdk.
> 
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> ---
>  arch/arm/boot/dts/da850-lcdk.dts | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm/boot/dts/da850-lcdk.dts b/arch/arm/boot/dts/da850-lcdk.dts
> index d864f11..1283263 100644
> --- a/arch/arm/boot/dts/da850-lcdk.dts
> +++ b/arch/arm/boot/dts/da850-lcdk.dts
> @@ -285,6 +285,7 @@
>  
>  &display {
>  	status = "okay";
> +	max-pixelclock = <37500>;

Should this not be in da850.dtsi since its an SoC imposed constraint? If
a board needs narrower constraint, it can override it. But I guess most
well designed boards will just hit the SoC constraint.

Thanks,
Sekhar

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#1532223 — Re: [PATCH v2 2/2] ARM: dts: da850-lcdk: specify the maximum pixel clock rate for tilcdc

2016-11-29 11:53 GMT+01:00 Sekhar Nori <nsekhar@ti.com>:
> On Monday 28 November 2016 05:45 PM, Bartosz Golaszewski wrote:
>> Due to memory throughput constraints any display mode for which the
>> pixel clock rate exceeds the recommended value of 37500 KHz must be
>> filtered out.
>
> I think there might be more reasons than memory throughput constraints
> for the reasoning behind 37.5Mhz cap on pixel clock. Why not just refer
> to the datasheet section that places this constraint so we know its a
> hardware restriction.
>
>>
>> Specify the max-pixelclock property for the display node for
>> da850-lcdk.
>>
>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
>> ---
>>  arch/arm/boot/dts/da850-lcdk.dts | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/arm/boot/dts/da850-lcdk.dts b/arch/arm/boot/dts/da850-lcdk.dts
>> index d864f11..1283263 100644
>> --- a/arch/arm/boot/dts/da850-lcdk.dts
>> +++ b/arch/arm/boot/dts/da850-lcdk.dts
>> @@ -285,6 +285,7 @@
>>
>>  &display {
>>       status = "okay";
>> +     max-pixelclock = <37500>;
>
> Should this not be in da850.dtsi since its an SoC imposed constraint? If
> a board needs narrower constraint, it can override it. But I guess most
> well designed boards will just hit the SoC constraint.
>

Both issues fixed in v3.

Thanks,
Bartosz Golaszewski

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