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References: <20220905100416.42421-1-angelogioacchino.delregno@collabora.com> <20220905100416.42421-9-angelogioacchino.delregno@collabora.com>
In-Reply-To: <20220905100416.42421-9-angelogioacchino.delregno@collabora.com>
From:   Chen-Yu Tsai <wenst@chromium.org>
Date:   Wed, 7 Sep 2022 11:49:55 +0800
Message-ID: <CAGXv+5G52--wF=e=nd3ezDPoQcOdsqMd_1WdzGEWxjjZaJsRLg@mail.gmail.com>
Subject: Re: [PATCH 08/10] clk: mediatek: clk-mt8195-topckgen: Drop univplls
 from mfg mux parents
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>
Cc:     matthias.bgg@gmail.com, mturquette@baylibre.com, sboyd@kernel.org,
        miles.chen@mediatek.com, rex-bc.chen@mediatek.com,
        nfraprado@collabora.com, chun-jie.chen@mediatek.com,
        jose.exposito89@gmail.com, drinkcat@chromium.org,
        weiyi.lu@mediatek.com, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-clk@vger.kernel.org, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org
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Precedence: bulk

Hi,

On Mon, Sep 5, 2022 at 6:04 PM AngeloGioacchino Del Regno
<angelogioacchino.delregno@collabora.com> wrote:
>
> These PLLs are conflicting with GPU rates that can be generated by
> the GPU-dedicated MFGPLL and would require a special clock handler
> to be used, for very little and ignorable power consumption benefits.
> Also, we're in any case unable to set the rate of these PLLs to
> something else that is sensible for this task, so simply drop them:
> this will make the GPU to be clocked exclusively from MFGPLL for
> "fast" rates, while still achieving the right "safe" rate during
> PLL frequency locking.
>
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
> ---
>  drivers/clk/mediatek/clk-mt8195-topckgen.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/drivers/clk/mediatek/clk-mt8195-topckgen.c b/drivers/clk/mediatek/clk-mt8195-topckgen.c
> index 4dde23bece66..6ff610c101ae 100644
> --- a/drivers/clk/mediatek/clk-mt8195-topckgen.c
> +++ b/drivers/clk/mediatek/clk-mt8195-topckgen.c
> @@ -301,8 +301,6 @@ static const char * const ipu_if_parents[] = {
>  static const char * const mfg_parents[] = {
>         "clk26m",
>         "mainpll_d5_d2",
> -       "univpll_d6",
> -       "univpll_d7"

I'd just comment them out and leave a note about it. Or remove them but
leave a note. Removed code will not be obvious to others. And given this
is probably the only public documentation of the hardware, it'd be a shame
to lose evidence of it.

ChenYu