[PATCH 3/4] clk: samsung: Add driver to control CLKOUT line on Exynos SoCs
s.nawrocki at samsung.com
Thu May 22 05:10:46 PDT 2014
On 22/05/14 13:44, Tushar Behera wrote:
> On 22 May 2014 16:04, Tomasz Figa <t.figa at samsung.com> wrote:
>> On 22.05.2014 07:13, Tushar Behera wrote:
>>> On 05/20/2014 10:13 PM, Tomasz Figa wrote:
>>>> This patch introduces a driver that handles configuration of CLKOUT pin
>>>> of Exynos SoCs that can be used to output certain clocks from inside of
>>>> the SoC to a dedicated output pin.
>>>> Signed-off-by: Tomasz Figa <t.figa at samsung.com>
>>>> .../devicetree/bindings/arm/samsung/pmu.txt | 30 ++++
>>>> drivers/clk/samsung/Makefile | 1 +
>>>> drivers/clk/samsung/clk-exynos-clkout.c | 153 +++++++++++++++++++++
>>>> 3 files changed, 184 insertions(+)
>>>> create mode 100644 drivers/clk/samsung/clk-exynos-clkout.c
>>> [ ... ]
>>>> + clkout->clk_table = clk_register_composite(NULL, "clkout",
>>>> + parent_names, parent_count, &clkout->mux.hw,
>>>> + &clk_mux_ops, NULL, NULL, &clkout->gate.hw,
>>>> + &clk_gate_ops, CLK_SET_RATE_PARENT
>>>> + | CLK_SET_RATE_NO_REPARENT);
>>> Would you please remove CLK_SET_RATE_NO_REPARENT flag from here? Let me
>>> know if you have reservations against this.
>> The problem with clock reparenting is that there are certain parent
>> clocks of CLKOUT, rate of which changes at runtime, e.g. clocks derived
>> from APLL or bus clocks, which can be reconfigured by cpufreq or devfreq.
> +CC: Sylwester Nawrocki
> Okay. But in cases where there is only 1 valid parent clock provided
> through DT (at the moment for Exynos5250/Exynos5420), would it be safe
> to set that clock as the parent of CLKOUT? Otherwise, this clock is
> not usable ATM.
I'd prefer to not allow re-parenting here, as it will not work in all system
configurations and seems not reliable in general.
>>> With RFC patches, I am able to do a clk_set_rate() on this clock to
>>> get a 24MHz output to the codec clock. With this flag set, I again have
>>> to rely on the default value set to this register in bootloader.
>> This problem should be handled by initializing clocks from DT. I'm not
>> sure why it hasn't been implemented yet...
> I would be happy to get it done that way. I can see a patch from
> Sylwester regarding this, but there hasn't been a conclusion as of
I posted a next version recently , any feedback on that is welcome.
I used these patches for the camera on Trats2 and the audio on Odroid U3
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