linux-kernel - Re: [PATCH 1/3] clk: qcom: clk-alpha-pll: add support for zonda pll

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Message-ID: <abc662f3-8c36-862d-4d50-3628d3a02ee2@marek.ca>
Date:   Tue, 18 May 2021 09:06:23 -0400
From:   Jonathan Marek <jonathan@...ek.ca>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     linux-arm-msm@...r.kernel.org, robert.foss@...aro.org,
        andrey.konovalov@...aro.org, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        "open list:COMMON CLK FRAMEWORK" <linux-clk@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] clk: qcom: clk-alpha-pll: add support for zonda pll

On 5/18/21 7:32 AM, Vinod Koul wrote:
> On 13-05-21, 13:52, Jonathan Marek wrote:

...

>> +/* ZONDA PLL specific */
>> +#define ZONDA_PLL_OUT_MASK	0xf
>> +#define ZONDA_STAY_IN_CFA	BIT(16)
>> +#define ZONDA_PLL_FREQ_LOCK_DET	BIT(29)
> 
> This seems similar to ALPHA_PLL_ACK_LATCH..?
> 

The bit is the same, and it is also used with wait_for_pll(), but the 
meaning seems different (the usage pattern is different).

>> +const struct clk_ops clk_alpha_pll_postdiv_zonda_ops = {
>> +	.recalc_rate = clk_alpha_pll_postdiv_fabia_recalc_rate,
>> +	.round_rate = clk_alpha_pll_postdiv_fabia_round_rate,
>> +	.set_rate = clk_alpha_pll_postdiv_fabia_set_rate,
>> +};
>> +EXPORT_SYMBOL(clk_alpha_pll_postdiv_zonda_ops);
> 
> Why add one more ops when we can reuse clk_alpha_pll_postdiv_fabia_ops
> for this?
> 

No reason (copied from downstream), will fix.

>> +
>> +	/* Set operation mode to OFF */
>> +	regmap_write(regmap, PLL_OPMODE(pll), PLL_STANDBY);
>> +
>> +	/* PLL should be in OFF mode before continuing */
>> +	wmb();
> 
> Why a barrier?
> 

Again no reason (copied from downstream, but it doesn't make sense to 
have this barrier).

>> +static unsigned long
>> +clk_zonda_pll_recalc_rate(struct clk_hw *hw, unsigned long parent_rate)
>> +{
>> +	struct clk_alpha_pll *pll = to_clk_alpha_pll(hw);
>> +	u32 l, frac;
>> +
>> +	regmap_read(pll->clkr.regmap, PLL_L_VAL(pll), &l);
>> +	regmap_read(pll->clkr.regmap, PLL_ALPHA_VAL(pll), &frac);
>> +
>> +	return alpha_pll_calc_rate(parent_rate, l, frac, ALPHA_BITWIDTH);
>> +}
> 
> sounds like you could use clk_trion_pll_recalc_rate() instead
> 

I had this thought as well, but alpha_width in 
clk_trion_pll_recalc()_rate is 16, here ALPHA_BITWIDTH is 32, so I just 
copied this from downstream.

I think changing pll_alpha_width() to return the right value for zonda 
will work and allow sharing the function, if you think that's a good idea?