linux-kernel - Re: [PATCH v6 20/41] ARM: da830: add new clock init using common clock framework

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Date:   Mon, 5 Feb 2018 16:36:58 +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 20/41] ARM: da830: add new clock init using common
 clock framework

On Friday 02 February 2018 11:33 PM, David Lechner wrote:
> On 02/02/2018 08:12 AM, Sekhar Nori wrote:
>> On Saturday 20 January 2018 10:43 PM, David Lechner wrote:
>>>   void __init da830_init_time(void)
>>>   {
>>> +#ifdef CONFIG_COMMON_CLK
>>> +    void __iomem *pll0, *psc0, *psc1;
>>> +    struct clk *clk;
>>> +
>>> +    pll0 = ioremap(DA8XX_PLL0_BASE, SZ_4K);
>>> +    psc0 = ioremap(DA8XX_PSC0_BASE, SZ_4K);
>>> +    psc1 = ioremap(DA8XX_PSC1_BASE, SZ_4K);
>>> +
>>> +    da8xx_register_cfgchip();
>>> +
>>> +    clk_register_fixed_rate(NULL, "ref_clk", NULL, 0, DA830_REF_FREQ);
>>> +
>>> +    da830_pll_clk_init(pll0);
>>> +
>>> +    da830_psc_clk_init(psc0, psc1);
>>> +
>>
>>> +    clk = clk_register_fixed_factor(NULL, "i2c0", "pll0_aux_clk", 0,
>>> 1, 1);
>>> +    clk_register_clkdev(clk, NULL, "i2c_davinci.1");
>>> +
>>> +    clk = clk_register_fixed_factor(NULL, "timer0", "pll0_aux_clk",
>>> 0, 1, 1);
>>> +    clk_register_clkdev(clk, "timer0", NULL);
>>> +
>>> +    clk = clk_register_fixed_factor(NULL, "timer1", "pll0_aux_clk",
>>> 0, 1, 1);
>>> +    clk_register_clkdev(clk, NULL, "davinci-wdt");
>>
>> Isn't this better done in da830_pll_clk_init() ? I think we can get rid
>> of the dummy fixed factor clock too and directly use the pll0_auxclk.
> 
> 
> I considered it, but I kind of like keeping the fixed factor clocks for
> debugging purposes. If you just have "pll0_auxclk" the enable count is
> not helpful because you don't know which driver did the enabling.

I think it is better to more or less reflect the hardware here. We would
not be doing this in the DT case, for example.

I see your point on debugging. Such code can perhaps be temporarily
introduced if really debugging such an issue. This will be the case with
any shared clock.

Thanks,
Sekhar