linux-kernel - Re: [PATCH V3 3/6] clk: meson: S4: add support for Amlogic S4 SoC PLL clock driver

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Date:   Mon, 29 Aug 2022 11:48:21 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Yu Tu <yu.tu@...ogic.com>, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: Re: [PATCH V3 3/6] clk: meson: S4: add support for Amlogic S4 SoC
 PLL clock driver


On Mon 15 Aug 2022 at 21:20, Yu Tu <yu.tu@...ogic.com> wrote:

>>>> +
>>>> +static struct clk_regmap s4_hdmi_pll_dco = {
>>>> +    .data = &(struct meson_clk_pll_data){
>>>> +        .en = {
>>>> +            .reg_off = ANACTRL_HDMIPLL_CTRL0,
>>>> +            .shift   = 28,
>>>> +            .width   = 1,
>>>> +        },
>>>> +        .m = {
>>>> +            .reg_off = ANACTRL_HDMIPLL_CTRL0,
>>>> +            .shift   = 0,
>>>> +            .width   = 8,
>>>> +        },
>>>> +        .n = {
>>>> +            .reg_off = ANACTRL_HDMIPLL_CTRL0,
>>>> +            .shift   = 10,
>>>> +            .width   = 5,
>>>> +        },
>>>> +        .frac = {
>>>> +            .reg_off = ANACTRL_HDMIPLL_CTRL1,
>>>> +            .shift   = 0,
>>>> +            .width   = 17,
>>>> +        },
>>>> +        .l = {
>>>> +            .reg_off = ANACTRL_HDMIPLL_CTRL0,
>>>> +            .shift   = 31,
>>>> +            .width   = 1,
>>>> +        },
>>>> +        .rst = {
>>>> +            .reg_off = ANACTRL_HDMIPLL_CTRL0,
>>>> +            .shift   = 29,
>>>> +            .width   = 1,
>>>> +        },
>>>> +    },
>>>> +    .hw.init = &(struct clk_init_data){
>>>> +        .name = "hdmi_pll_dco",
>>>> +        .ops = &meson_clk_pll_ro_ops,
>>>> +        .parent_data = (const struct clk_parent_data []) {
>>>> +            { .fw_name = "xtal", }
>>>> +        },
>>>> +        .num_parents = 1,
>>>> +        /*
>>>> +         * Display directly handle hdmi pll registers ATM, we need
>>>> +         * NOCACHE to keep our view of the clock as accurate as
>>>> +         * possible
>>>> +         */
>>>
>>> Is it really ?
>>>
>>> Given that HDMI support for the s4 is there yet, the
>>> addresses have changes and the region is no longer a syscon, it is time
>>> for the HDMI driver to get fixed.
> The HDMI PLL is configured in the Uboot phase and does not change the
> frequency in the kernel phase. So we use the NOCACHE flag and
> "ro_ops".

That's no reason to put NOCACHE or ro-ops

If you want the frequencies to be statically assinged, the correct way
would be through assigned-rate in DT I guess.