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

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Message-ID: <b87ab80d-0936-5a5a-25da-35c0dbdede33@linaro.org>
Date:   Fri, 13 Jan 2023 16:20:06 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     devi priya <quic_devipriy@...cinc.com>, 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,
        dmitry.baryshkov@...aro.org, 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 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.

> 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
> 
> 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,
>  	},
>  };