linux-kernel - Re: [PATCH 6/6] clk: qcom: Fix APSS PLL and RCG Configuration

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Message-ID: <f21b74b2-cdaf-1be1-17e7-d004bfdddedd@quicinc.com>
Date:   Wed, 1 Feb 2023 20:10:52 +0530
From:   Devi Priya <quic_devipriy@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>, <agross@...nel.org>,
        <andersson@...nel.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <mturquette@...libre.com>,
        <sboyd@...nel.org>, <jassisinghbrar@...il.com>,
        <catalin.marinas@....com>, <will@...nel.org>,
        <shawnguo@...nel.org>, <arnd@...db.de>,
        <marcel.ziswiler@...adex.com>, <nfraprado@...labora.com>,
        <broonie@...nel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-clk@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     <quic_srichara@...cinc.com>, <quic_gokulsri@...cinc.com>,
        <quic_sjaganat@...cinc.com>, <quic_kathirav@...cinc.com>,
        <quic_arajkuma@...cinc.com>, <quic_anusha@...cinc.com>,
        <quic_poovendh@...cinc.com>
Subject: Re: [PATCH 6/6] clk: qcom: Fix APSS PLL and RCG Configuration



On 1/31/2023 3:10 PM, Dmitry Baryshkov wrote:
> On 31/01/2023 11:17, Devi Priya wrote:
>> Thanks for taking time to review the patch
>>
>> On 1/13/2023 8:50 PM, Konrad Dybcio wrote:
>>>
>>>
>>> On 13.01.2023 15:36, devi priya wrote:
>>>> Included CLK_IS_CRITICAL flag which helps to properly enable
>>>> the APSS PLL during bootup.
>>> Please describe the issue and not only the user-visible impact it
>>> makes. Does the PLL get shut down by clk_ignore_unused? Maybe you
>>> would be interested in the sync_state changes that landed in recent
>>> -next that may solve it for you?
>>>
>>> I don't think it should be always-on, as you have an alternate source
>>> for low power modes, adding CLK_IS_CRITICAL will keep the PLL enabled
>>> even if you're not using it.
>> Yeah, got it. Will drop the critical flag
>>>
>>>> clk_rcg2_ops should be used for APSS clock RCG, as other ops
>>>> will not configure the RCG register
>>> RCG register meaning RCG register*s*, meaning in this case M/N/D
>>> which would be required for proper rate setting and not only input
>>> switching (which arguably doesn't seem to be of much concern on a
>>> single-parent clock)? This all is not obvious..
>>>
>>> Konrad
>> The source selection is done by configuring the RCGR config register 
>> with the source entry (P_APSS_PLL_EARLY) added to the frequency table. 
>> Proper rate is achieved by configuring the PLL and hence M/N/D values 
>> are not configured
> 
> But the clk_rcg2_mux_closest_ops also programs the parent for the clock. 
> So from your description it isn't obvious what is wrong with the current 
> _ops used for the clock.
> 
Okay, understood & agreed.
Will re-verify it once and update it accordingly in V2
>>>>
>>>> Co-developed-by: Praveenkumar I <quic_ipkumar@...cinc.com>
>>>> Signed-off-by: Praveenkumar I <quic_ipkumar@...cinc.com>
>>>> Signed-off-by: devi priya <quic_devipriy@...cinc.com>
>>>> ---
>>>>   drivers/clk/qcom/apss-ipq-pll.c | 1 +
>>>>   drivers/clk/qcom/apss-ipq6018.c | 8 +++++++-
>>>>   2 files changed, 8 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/clk/qcom/apss-ipq-pll.c 
>>>> b/drivers/clk/qcom/apss-ipq-pll.c
>>>> index dd0c01bf5a98..75486a124fcd 100644
>>>> --- a/drivers/clk/qcom/apss-ipq-pll.c
>>>> +++ b/drivers/clk/qcom/apss-ipq-pll.c
>>>> @@ -33,6 +33,7 @@ static struct clk_alpha_pll ipq_pll = {
>>>>               },
>>>>               .num_parents = 1,
>>>>               .ops = &clk_alpha_pll_huayra_ops,
>>>> +            .flags = CLK_IS_CRITICAL,
>>>>           },
>>>>       },
>>>>   };
>>>> diff --git a/drivers/clk/qcom/apss-ipq6018.c 
>>>> b/drivers/clk/qcom/apss-ipq6018.c
>>>> index f2f502e2d5a4..0d0e7196a4dc 100644
>>>> --- a/drivers/clk/qcom/apss-ipq6018.c
>>>> +++ b/drivers/clk/qcom/apss-ipq6018.c
>>>> @@ -33,15 +33,21 @@ static const struct parent_map 
>>>> parents_apcs_alias0_clk_src_map[] = {
>>>>       { P_APSS_PLL_EARLY, 5 },
>>>>   };
>>>> +static const struct freq_tbl ftbl_apcs_alias0_clk_src[] = {
>>>> +    { .src = P_APSS_PLL_EARLY, .pre_div = 1 },
>>>> +    { }
>>>> +};
>>>> +
>>>>   static struct clk_rcg2 apcs_alias0_clk_src = {
>>>>       .cmd_rcgr = 0x0050,
>>>> +    .freq_tbl = ftbl_apcs_alias0_clk_src,
>>>>       .hid_width = 5,
>>>>       .parent_map = parents_apcs_alias0_clk_src_map,
>>>>       .clkr.hw.init = &(struct clk_init_data){
>>>>           .name = "apcs_alias0_clk_src",
>>>>           .parent_data = parents_apcs_alias0_clk_src,
>>>>           .num_parents = ARRAY_SIZE(parents_apcs_alias0_clk_src),
>>>> -        .ops = &clk_rcg2_mux_closest_ops,
>>>> +        .ops = &clk_rcg2_ops,
>>>>           .flags = CLK_SET_RATE_PARENT,
>>>>       },
>>>>   };
>> Best Regards,
>> Devi Priya
> 
Best Regards,
Devi Priya