linux-kernel - Re: [PATCH v6 04/41] clk: davinci: Add platform information for TI DA850 PLL

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Date:   Fri, 2 Feb 2018 13:53:04 +0530
From:   Sekhar Nori <nsekhar@...com>
To:     David Lechner <david@...hnology.com>, <linux-clk@...r.kernel.org>,
        <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Kevin Hilman <khilman@...nel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Adam Ford <aford173@...il.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 04/41] clk: davinci: Add platform information for TI
 DA850 PLL

On Friday 02 February 2018 12:34 AM, David Lechner wrote:
> On 02/01/2018 02:58 AM, Sekhar Nori wrote:
>> On Saturday 20 January 2018 10:43 PM, David Lechner wrote:
>>> This adds platform-specific declarations for the PLL clocks on TI DA850/
>>> OMAP-L138/AM18XX SoCs.
>>>
>>> Signed-off-by: David Lechner <david@...hnology.com>
>>
>>> +static const struct davinci_pll_clk_info da850_pll1_info __initconst
>>> = {
>>> +    .name = "pll1",
>>> +    .unlock_reg = CFGCHIP(3),
>>> +    .unlock_mask = CFGCHIP3_PLL1_MASTER_LOCK,
>>
>> I guess this will change with the cfgchip handling discussion last week.
> 
> Actually no, there really weren't any changes to the clock drivers because
> of this change. Only a small change in mach-davinci.
> 
>>
>>> +    .pllm_mask = GENMASK(4, 0),
>>> +    .pllm_min = 4,
>>> +    .pllm_max = 32,
>>> +    .pllout_min_rate = 300000000,
>>> +    .pllout_max_rate = 600000000,
>>> +    .flags = PLL_HAS_POSTDIV,
>>> +};
>>> +
>>
>> [...]
>>
>>> +void __init da850_pll_clk_init(void __iomem *pll0, void __iomem *pll1)
>>> +{
>>> +    const struct davinci_pll_sysclk_info *info;
>>> +
>>> +    davinci_pll_clk_register(&da850_pll0_info, "ref_clk", pll0);
>>> +
>>> +    davinci_pll_auxclk_register("pll0_auxclk", pll0);
>>> +
>>> +    for (info = da850_pll0_sysclk_info; info->name; info++)
>>> +        davinci_pll_sysclk_register(info, pll0);
>>> +
>>> +    davinci_pll_obsclk_register(&da850_pll0_obsclk_info, pll0);
>>> +
>>> +    davinci_pll_clk_register(&da850_pll1_info, "oscin", pll1);
>>
>> Both PLL0 and PLL1 use the same reference clock. So this should be
>> "ref_clk". I dont think we ever need to register a clock called oscin
>> along with "ref_clk". There is only one reference clock. It can either
>> be obtained using internal oscillator or external oscillator.
>>
> 
> As per my response to the previous path, this depends on which both
> which SoC and which diagram in the TRM for that SoC you are looking at.
> It works either way.

I see the distinction you are making between clock inputs to the two
PLLs now. A comment somewhere (probably in pll.c) should do it.

Thanks,
Sekhar