linux-kernel - Re: [PATCH v2 11/11] clk: qcom: gpucc-msm8998: Allow fabia gpupll0 rate setting

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Message-ID: <161280865244.76967.4923517866545833837@swboyd.mtv.corp.google.com>
Date:   Mon, 08 Feb 2021 10:24:12 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        linux-arm-msm@...r.kernel.org
Cc:     konrad.dybcio@...ainline.org, marijn.suijten@...ainline.org,
        martin.botka@...ainline.org, phone-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org, agross@...nel.org,
        bjorn.andersson@...aro.org, mturquette@...libre.com,
        robh+dt@...nel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>
Subject: Re: [PATCH v2 11/11] clk: qcom: gpucc-msm8998: Allow fabia gpupll0 rate setting

Quoting AngeloGioacchino Del Regno (2021-01-14 14:10:59)
> The GPU PLL0 is not a fixed PLL and the rate can be set on it:
> this is necessary especially on boards which bootloader is setting
> a very low rate on this PLL before booting Linux, which would be
> unsuitable for postdividing to reach the maximum allowed Adreno GPU
> frequency of 710MHz (or, actually, even 670MHz..) on this SoC.
> 
> To allow setting rates on the GPU PLL0, also define VCO boundaries
> and set the CLK_SET_RATE_PARENT flag to the GPU PLL0 postdivider.
> 
> With this change, the Adreno GPU is now able to scale through all
> the available frequencies.

BTW, you're probably undervolting your GPU and clocking it higher
than it should be at the voltage from boot.

> 
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...ainline.org>
> ---
>  drivers/clk/qcom/gpucc-msm8998.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/qcom/gpucc-msm8998.c b/drivers/clk/qcom/gpucc-msm8998.c
> index 1a518c4915b4..fedfffaf0a8d 100644
> --- a/drivers/clk/qcom/gpucc-msm8998.c
> +++ b/drivers/clk/qcom/gpucc-msm8998.c
> @@ -50,6 +50,11 @@ static struct clk_branch gpucc_cxo_clk = {
>         },
>  };
>  
> +static struct pll_vco fabia_vco[] = {

Should be const.

> +       { 249600000, 2000000000, 0 },
> +       { 125000000, 1000000000, 1 },
> +};
> +
>  static const struct clk_div_table post_div_table_fabia_even[] = {
>         { 0x0, 1 },
>         { 0x1, 2 },