linux-kernel - Re: [PATCH] clk: sunxi-ng: sun6i-a31: Force AHB1 clock to use PLL6 as parent

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Date:   Tue, 18 Oct 2016 15:57:29 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Jean-Francois Moine <moinejf@...e.fr>
Cc:     Chen-Yu Tsai <wens@...e.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        linux-sunxi <linux-sunxi@...glegroups.com>,
        linux-clk <linux-clk@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] clk: sunxi-ng: sun6i-a31: Force AHB1 clock to use PLL6 as parent

On Tue, Oct 18, 2016 at 3:50 PM, Jean-Francois Moine <moinejf@...e.fr> wrote:
> On Tue, 18 Oct 2016 13:42:09 +0800
> Chen-Yu Tsai <wens@...e.org> wrote:
>
>> On the A31, the DMA engine only works if AHB1 is clocked from PLL6.
>> In addition, the hstimer is clocked from AHB1, and if AHB1 is clocked
>> from the CPU clock, and cpufreq is working, we get an unstable timer.
>>
>> Force the AHB1 clock to use PLL6 as its parent. Previously this was done
>> in the device tree with the assigned-clocks and assigned-clocks-parent
>> bindings. However with this new monolithic driver, the system critical
>> clocks aren't exported through the device tree. The alternative is to
>> force this setting in the driver before the clocks are registered.
>
> It should be simpler to export the constant (CLK_AHB1) instead of
> adding code...

I get you. But the plan is to not export system core clocks that
don't have a direct user.

ChenYu