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

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Date:   Fri, 22 Jan 2021 09:37:03 +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 1/22/21 8:46 AM, Laurent Pinchart wrote:
> Hi Michal,
> 
> On Fri, Jan 22, 2021 at 08:19:15AM +0100, Michal Simek wrote:
>> On 1/21/21 11:37 PM, Laurent Pinchart wrote:
>>> 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.
> 
> Unless I'm mistaken, on the ZCU106 board, the chip is an SI5341B, which
> has a driver already. I tried to declare it in DT, but the PS_REF_CLK
> then got disabled at the end of boot, and the system wasn't happy about
> it :-)

In series before si5341 chips are enabled as the part of sata
enablement. Maybe you missed always-on parameter.

si5341_9: out@9 {
	/* refclk9 used for PS_REF_CLK 33.3 MHz */
	reg = <9>;
	always-on;
};

I just retest it and I can't see any issue. Sata
I see DP driver probed but I can't see anything on 4k monitor but maybe
there should be something to setup (I use fs from 2015).

thanks,
Michal