linux-kernel - Re: [PATCH v2 1/3] clk: qcom: clk-alpha-pll: Add support for controlling Agera PLLs

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Message-ID: <1d969460-92c7-ce9a-d727-2c0a31c5d3c5@codeaurora.org>
Date:   Sat, 17 Oct 2020 00:08:58 +0530
From:   Taniya Das <tdas@...eaurora.org>
To:     Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>
Cc:     David Brown <david.brown@...aro.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andy Gross <agross@...nel.org>, devicetree@...r.kernel.org,
        robh@...nel.org, robh+dt@...nel.org
Subject: Re: [PATCH v2 1/3] clk: qcom: clk-alpha-pll: Add support for
 controlling Agera PLLs

Thanks Stephen for the review comments.

On 10/14/2020 7:37 AM, Stephen Boyd wrote:
> Quoting Taniya Das (2020-10-13 10:11:48)
>> diff --git a/drivers/clk/qcom/clk-alpha-pll.c b/drivers/clk/qcom/clk-alpha-pll.c
>> index 26139ef..17e1fc0 100644
>> --- a/drivers/clk/qcom/clk-alpha-pll.c
>> +++ b/drivers/clk/qcom/clk-alpha-pll.c
>> @@ -1561,3 +1571,73 @@ const struct clk_ops clk_alpha_pll_postdiv_lucid_ops = {
>>          .set_rate = clk_alpha_pll_postdiv_fabia_set_rate,
>>   };
>>   EXPORT_SYMBOL_GPL(clk_alpha_pll_postdiv_lucid_ops);
>> +
>> +void clk_agera_pll_configure(struct clk_alpha_pll *pll, struct regmap *regmap,
>> +                       const struct alpha_pll_config *config)
>> +{
>> +       if (config->l)
>> +               regmap_write(regmap, PLL_L_VAL(pll), config->l);
> 
> Maybe make a helper function for this too. That way we can't mix up the
> if condition with the value in the write.
> 

Sure, I will add a helper function.

> 	clk_alpha_pll_write_config(regmap, PLL_L_VAL(pll), config->l);
> 
> static void clk_alpha_pll_write_config(struct regmap *regmap,
> 				       unsigned int reg,
> 				       unsigned int val) {
> 	if (val)
> 		regmap_write(regmap, reg, val);
> }
> 
> and how are we so lucky that zero isn't a value that we may need to
> write?
> 
>> +
>> +       if (config->alpha)
>> +               regmap_write(regmap, PLL_ALPHA_VAL(pll), config->alpha);
>> +
>> +       if (config->user_ctl_val)
>> +               regmap_write(regmap, PLL_USER_CTL(pll), config->user_ctl_val);
>> +
>> +       if (config->config_ctl_val)
>> +               regmap_write(regmap, PLL_CONFIG_CTL(pll),
>> +                                               config->config_ctl_val);
>> +
>> +       if (config->config_ctl_hi_val)
>> +               regmap_write(regmap, PLL_CONFIG_CTL_U(pll),
>> +                                               config->config_ctl_hi_val);
>> +
>> +       if (config->test_ctl_val)
>> +               regmap_write(regmap, PLL_TEST_CTL(pll),
>> +                                               config->test_ctl_val);
>> +
>> +       if (config->test_ctl_hi_val)
>> +               regmap_write(regmap,  PLL_TEST_CTL_U(pll),
>> +                                               config->test_ctl_hi_val);
>> +}
>> +EXPORT_SYMBOL_GPL(clk_agera_pll_configure);
>> +
>> +static int clk_alpha_pll_agera_set_rate(struct clk_hw *hw, unsigned long rate,
>> +                                                       unsigned long prate)
>> +{
>> +       struct clk_alpha_pll *pll = to_clk_alpha_pll(hw);
>> +       u32 l, alpha_width = pll_alpha_width(pll);
>> +       unsigned long rrate, max = rate + PLL_RATE_MARGIN;
>> +       u64 a;
>> +
>> +       rrate = alpha_pll_round_rate(rate, prate, &l, &a, alpha_width);
>> +
>> +       /*
>> +        * Due to limited number of bits for fractional rate programming, the
>> +        * rounded up rate could be marginally higher than the requested rate.
>> +        */
>> +       if (rrate > (rate + PLL_RATE_MARGIN) || rrate < rate) {
>> +               pr_err("%s: Rounded rate %lu not within range [%lu, %lu)\n",
>> +                      clk_hw_get_name(hw), rrate, rate, max);
>> +               return -EINVAL;
>> +       }
> 
> Can this be extracted into a helper function?
> 

Yes, I will add this too.

>> +
>> +       /* change L_VAL without having to go through the power on sequence */
>> +       regmap_write(pll->clkr.regmap, PLL_L_VAL(pll), l);
>> +       regmap_write(pll->clkr.regmap, PLL_ALPHA_VAL(pll), a);
>> +
>> +       if (clk_hw_is_enabled(hw))
>> +               return wait_for_pll_enable_lock(pll);
>> +
>> +       return 0;
>> +}
>> +

-- 
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of Code Aurora Forum, hosted by The Linux Foundation.

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