linux-kernel - Re: [PATCH 3/3] arm64: dts: zynqmp: Wire up the DisplayPort subsystem

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Date:   Fri, 22 Jan 2021 08:19:15 +0100
From:   Michal Simek <michal.simek@...inx.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Michal Simek <michal.simek@...inx.com>
CC:     <linux-kernel@...r.kernel.org>, <monstr@...str.eu>,
        <git@...inx.com>, Krzysztof Kozlowski <krzk@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 3/3] arm64: dts: zynqmp: Wire up the DisplayPort subsystem

Hi Laurent,

On 1/21/21 11:37 PM, Laurent Pinchart wrote:
> Hi Michal,
> 
> Thank you for the patch.
> 
> On Thu, Jan 21, 2021 at 01:36:07PM +0100, Michal Simek wrote:
>> From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
>>
>> Enable the dpsub device and wire it up to the PS-GTR PHY lanes routed to
>> the DisplayPort connector.
>>
>> Signed-off-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
>> Signed-off-by: Michal Simek <michal.simek@...inx.com>
>> ---
>>
>> Wire all the boards
>>
>> ---
>>  .../boot/dts/xilinx/zynqmp-zcu100-revC.dts    | 31 +++++++++++++++++++
>>  .../boot/dts/xilinx/zynqmp-zcu102-revA.dts    | 10 ++++++
>>  .../boot/dts/xilinx/zynqmp-zcu104-revA.dts    | 11 +++++++
>>  .../boot/dts/xilinx/zynqmp-zcu104-revC.dts    | 11 +++++++
>>  .../boot/dts/xilinx/zynqmp-zcu106-revA.dts    | 11 +++++++
>>  .../boot/dts/xilinx/zynqmp-zcu111-revA.dts    | 11 +++++++
>>  6 files changed, 85 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/xilinx/zynqmp-zcu100-revC.dts b/arch/arm64/boot/dts/xilinx/zynqmp-zcu100-revC.dts
>> index 71ebcaadb7c8..a53598c3624b 100644
>> --- a/arch/arm64/boot/dts/xilinx/zynqmp-zcu100-revC.dts
>> +++ b/arch/arm64/boot/dts/xilinx/zynqmp-zcu100-revC.dts
>> @@ -15,6 +15,7 @@
>>  #include <dt-bindings/input/input.h>
>>  #include <dt-bindings/interrupt-controller/irq.h>
>>  #include <dt-bindings/gpio/gpio.h>
>> +#include <dt-bindings/phy/phy.h>
>>  
>>  / {
>>  	model = "ZynqMP ZCU100 RevC";
>> @@ -108,6 +109,18 @@ ina226 {
>>  		compatible = "iio-hwmon";
>>  		io-channels = <&u35 0>, <&u35 1>, <&u35 2>, <&u35 3>;
>>  	};
>> +
>> +	si5335a_0: clk26 {
>> +		compatible = "fixed-clock";
>> +		#clock-cells = <0>;
>> +		clock-frequency = <26000000>;
>> +	};
>> +
>> +	si5335a_1: clk27 {
>> +		compatible = "fixed-clock";
>> +		#clock-cells = <0>;
>> +		clock-frequency = <27000000>;
>> +	};
> 
> This is fine as a workaround for now, but I'm still wondering how we'll
> solve this properly. We can declare the SI5335A in DT without wiring the
> output that provides the clock to the PS, otherwise it will be disabled
> as part of the boot process.

All these clock chips are preprogrammed to certain rate and enabled by
default. It means there doesn't need to be any SW handling to enable it.
When driver for these clock chips comes we can change this that's why I
used labels which are saying which output it is.

Thanks,
Michal