linux-kernel - Re: [PATCH 2/6] clk: meson: add a driver for the Meson8/8b/8m2 DDR clock controller

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Date:   Wed, 02 Oct 2019 11:04:42 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        linux-amlogic@...ts.infradead.org, devicetree@...r.kernel.org,
        khilman@...libre.com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH 2/6] clk: meson: add a driver for the Meson8/8b/8m2 DDR clock controller


On Tue 01 Oct 2019 at 20:53, Martin Blumenstingl <martin.blumenstingl@...glemail.com> wrote:

>
> [...]
>> > +static struct clk_hw_onecell_data meson8_ddr_clk_hw_onecell_data = {
>> > +     .hws = {
>> > +             [DDR_CLKID_DDR_PLL_DCO]         = &meson8_ddr_pll_dco.hw,
>> > +             [DDR_CLKID_DDR_PLL]             = &meson8_ddr_pll.hw,
>>
>> I wonder if onecell is not overkill for this driver. We won't expose the
>> DCO, so only the post divider remains
>>
>> Do you expect this provider to have more than one leaf clock ?
>> If not, maybe you could use of_clk_hw_simple_get() instead ?
> there's some more clock bits in DDR_CLK_CNTL - the public A311D
> datasheet has a description for these bits but I'm not sure they do
> the same on Meson8/Meson8b/Meson8m2
> all I know is that some magic bytes are written to DDR_CLK_CNTL in the
> old u-boot code
>
> that's why I don't want to make any assumptions and play safe here (by
> using a onecell clock provider)

Understood. Let's keep onecell then.