linux-kernel - Re: [PATCH v4 6/8] arm64: dts: add SRAM, MHU mailbox and SCPI support on Juno

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Date:	Mon, 08 Jun 2015 15:32:56 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	"Jon Medhurst (Tixy)" <tixy@...aro.org>
CC:	Sudeep Holla <sudeep.holla@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Arnd Bergmann <arnd@...db.de>,
	Kevin Hilman <khilman@...nel.org>,
	Olof Johansson <olof@...om.net>
Subject: Re: [PATCH v4 6/8] arm64: dts: add SRAM, MHU mailbox and SCPI support
 on Juno



On 08/06/15 14:51, Jon Medhurst (Tixy) wrote:
> On Mon, 2015-06-08 at 11:40 +0100, Sudeep Holla wrote:
> [...]
>> +
>> +	scpi {
>> +		compatible = "arm,scpi";
>> +		mboxes = <&mailbox 1>;
>> +		shmem = <&cpu_scp_hpri>;
>> +
>> +		clocks {
>> +			compatible = "arm,scpi-clocks";
>> +
>> +			scpi_dvfs: scpi_clocks@0 {
>> +				compatible = "arm,scpi-dvfs-clocks";
>> +				#clock-cells = <1>;
>> +				clock-indices = <0>, <1>, <2>;
>> +				clock-output-names = "vbig", "vlittle", "vgpu";
>
>  From where do the clock names derive? They look more like names for
> voltage domains rather than clocks. My (admittedly very old) Juno docs,
> have the clocks as ATLCLK, APLCLK and GPUCLK.
>

I agree, I just copied it from SCPI spec which just deals with power
domain names in the context of DVFS. I will update as per Juno doc.

>> +			};
>> +			scpi_clk: scpi_clocks@3 {
>> +				compatible = "arm,scpi-variable-clocks";
>> +				#clock-cells = <1>;
>> +				clock-indices = <3>, <4>;
>> +				clock-output-names = "pxlclk0", "pxlclk1";
>
> Can we also have clock index 5, name 'i2s_clk', for used by audio?
> (I don't know what other clocks the SCP currently supports, but audio is
> one being currently used by the out-of-tree code).
>

I will update.

> Also, I believe that both display outputs share the same clock, and so
> pxlclk0 and pxlclk1 can't be controlled independently. But I guess these
> device-tree entries are for the interface to the SCP firmware, not the
> hardware, and if that pretends the clocks are independent...
>

Yes, this is bit tricky, I will let Liviu answer this.

Regards,
Sudeep
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