linux-kernel - Re: [RESEND PATCH v4] clk/axs10x: Add I2S PLL clock driver

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Date:	Wed, 20 Apr 2016 10:47:43 +0100
From:	Jose Abreu <Jose.Abreu@...opsys.com>
To:	Stephen Boyd <sboyd@...eaurora.org>,
	Jose Abreu <Jose.Abreu@...opsys.com>
CC:	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	<linux-kernel@...r.kernel.org>, <linux-clk@...r.kernel.org>,
	<linux-snps-arc@...ts.infradead.org>,
	<CARLOS.PALMINHA@...opsys.com>, <Alexey.Brodkin@...opsys.com>,
	<mturquette@...libre.com>
Subject: Re: [RESEND PATCH v4] clk/axs10x: Add I2S PLL clock driver

Hi Stephen,


On 20-04-2016 02:54, Stephen Boyd wrote:
> On 04/19, Jose Abreu wrote:
>> @Stephen: can you give some input so that I can submit a v6?
>>
> I don't prefer putting the second register in the same DT node,
> but that's really up to the DT reviewers to approve such a
> design. The current binding has been acked by Rob right?

Yes.

> Assuming the new binding is acked/reviewed then that solution is
> fine.

Ok, will then use the DT to pass the FPGA version register.

> Otherwise, I still prefer two DTS files for the two different FPGA
> versions. At the least, please use ioremap for any pointers that
> you readl/writel here.
>
> Beyond that, we should have a fixed rate source clk somewhere in
> the software view of the clk tree, because that reflects reality.
> Hardcoding the parent rate in the structure works, but doesn't
> properly express the clk tree.
>

Can I use a property in the DT to pass this reference clock? something like this:
    snps,parent-freq = <0xFBED9 27000000>, <0x0 28224000>; /* Tuple
<fpga-version reference-clock-freq>, fpga-version = 0 is default */

Or use a parent clock? like:
    clk {
        compatible = "fixed-clock";
        clock-frequency = <27000000>;
        #clock-cells = <0>;
        snps,fpga-version = <0xFBED9>;
    }

It is important to distinguish between the different versions automatically, is
any of these solutions ok?

Best regards,
Jose Miguel Abreu