linux-kernel - Re: [PATCH 3/5] clk: qcom: gcc-ipq6018: remove alpha values from NSS Crypto PLL's config

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Message-ID: <23d59aa6-ef46-46bd-94c9-a298b4870e09@gmail.com>
Date: Fri, 25 Oct 2024 22:06:55 +0200
From: Gabor Juhos <j4g8y7@...il.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Bjorn Andersson <andersson@...nel.org>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, linux-arm-msm@...r.kernel.org,
 linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] clk: qcom: gcc-ipq6018: remove alpha values from NSS
 Crypto PLL's config

2024. 10. 25. 8:18 keltezéssel, Dmitry Baryshkov írta:
> On Mon, Oct 21, 2024 at 10:21:59PM +0200, Gabor Juhos wrote:
>> Since both the 'alpha' and 'alpha_hi' members of the configuration is
>> initialized with zero values, the output rate of the PLL will be the
>> same whether alpha mode is enabled or not.
>>
>> Remove the initialization of the alpha* members to make it clear that
>> alpha mode is not required to get the desired output rate.
>>
>> While at it, also add a comment to indicate the frequency the PLL runs
>> at with the current configuration.
>>
>> No functional changes, the PLL runs at 1.2 GHz both before and after
>> the change.
>>
>> Tested on Xiaomi Mi Router AX1800 (IPQ6018, out-of-tree board).
>>
>> Signed-off-by: Gabor Juhos <j4g8y7@...il.com>
>> ---
>>  drivers/clk/qcom/gcc-ipq6018.c | 4 +---
>>  1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/drivers/clk/qcom/gcc-ipq6018.c b/drivers/clk/qcom/gcc-ipq6018.c
>> index ab0f7fc665a9790dd8edba0cf4b86c5c672a337d..d861191b0c85ccc105ac0e62d7a68210c621fc13 100644
>> --- a/drivers/clk/qcom/gcc-ipq6018.c
>> +++ b/drivers/clk/qcom/gcc-ipq6018.c
>> @@ -4194,10 +4194,9 @@ static const struct alpha_pll_config ubi32_pll_config = {
>>  	.test_ctl_hi_val = 0x4000,
>>  };
>>  
>> +/* 1200 MHz configuration */
>>  static const struct alpha_pll_config nss_crypto_pll_config = {
>>  	.l = 0x32,
>> -	.alpha = 0x0,
>> -	.alpha_hi = 0x0,
> 
> I'd say this serves documentation purposes: zero alpha value

For me, setting 'alpha_en_mask' means that the alpha values will be used. If it
is not set, then it means that the alpha values are getting ignored. If those
will be ignored eventually, specifying even zero alpha values explicitly is
pointless in my opinion.

If we really need that for documentation purposes, the comment before the
configuration can be changed to indicate that alpha values are not needed.

> 
>>  	.config_ctl_val = 0x4001055b,
>>  	.main_output_mask = BIT(0),
>>  	.pre_div_val = 0x0,
>> @@ -4206,7 +4205,6 @@ static const struct alpha_pll_config nss_crypto_pll_config = {
>>  	.post_div_mask = GENMASK(11, 8),
>>  	.vco_mask = GENMASK(21, 20),
>>  	.vco_val = 0x0,
>> -	.alpha_en_mask = BIT(24),
> 
> This is okay

Regards,
Gabor