linux-kernel - Re: [PATCH v5 02/44] clk: davinci: New driver for davinci PLL clocks

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Date:   Fri, 12 Jan 2018 20:13:41 -0600
From:   David Lechner <david@...hnology.com>
To:     Sekhar Nori <nsekhar@...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>,
        Adam Ford <aford173@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 02/44] clk: davinci: New driver for davinci PLL clocks

On 01/12/2018 03:21 AM, Sekhar Nori wrote:
> On Monday 08 January 2018 07:47 AM, David Lechner wrote:
>> +static unsigned long davinci_pll_clk_recalc(struct clk_hw *hw,
>> +					    unsigned long parent_rate)
>> +{
>> +	struct davinci_pll_clk *pll = to_davinci_pll_clk(hw);
>> +	unsigned long rate = parent_rate;
>> +	u32 prediv, mult, postdiv;
>> +
>> +	prediv = readl(pll->base + PREDIV) & PREDIV_RATIO_MASK;
>> +	mult = readl(pll->base + PLLM) & PLLM_MASK;
>> +	postdiv = readl(pll->base + POSTDIV) & POSTDIV_RATIO_MASK;
> 
> Shouldn't we check if the pre and post dividers are enabled before using
> them?

I dug into this and the answer is no. The enable bit acts like a gate, not
a bypass, so it does not affect the rate calculation.