linux-kernel - Re: [PATCH] clk: samsung: exynos7: Enable clocks for CMU_CCORE and CMU

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Message-ID: <CA+Ln22G0b1O9HHyePg60Q2uZnGT_a3J1LMU0o3+CpPoLCTbksA@mail.gmail.com>
Date:	Wed, 13 Apr 2016 09:26:15 +0300
From:	Tomasz Figa <tomasz.figa@...il.com>
To:	Alim Akhtar <alim.akhtar@...sung.com>
Cc:	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Thomas Abraham <thomas.ab@...sung.com>,
	Krzysztof Kozłowski <k.kozlowski@...sung.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>, linux-clk@...r.kernel.org,
	Stephen Boyd <sboyd@...eaurora.org>,
	Michael Turquette <mturquette@...libre.com>
Subject: Re: [PATCH] clk: samsung: exynos7: Enable clocks for CMU_CCORE and
 CMU_FSYS0 blocks

2016-04-12 14:07 GMT+03:00 Alim Akhtar <alim.akhtar@...sung.com>:
> This patch enables clocks for CMU_CCORE and CMU_FSYS0 blocks. This is
> required before accessing registers of these blocks.
>
> Signed-off-by: Alim Akhtar <alim.akhtar@...sung.com>
> ---
>  drivers/clk/samsung/clk-exynos7.c |    9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/drivers/clk/samsung/clk-exynos7.c b/drivers/clk/samsung/clk-exynos7.c
> index ad68d46..7013aa7 100644
> --- a/drivers/clk/samsung/clk-exynos7.c
> +++ b/drivers/clk/samsung/clk-exynos7.c
> @@ -8,6 +8,7 @@
>   *
>  */
>
> +#include <linux/clk.h>
>  #include <linux/clk-provider.h>
>  #include <linux/of.h>
>
> @@ -205,7 +206,11 @@ static struct samsung_cmu_info topc_cmu_info __initdata = {
>
>  static void __init exynos7_clk_topc_init(struct device_node *np)
>  {
> +       struct clk *clk;
> +
>         samsung_cmu_register_one(np, &topc_cmu_info);
> +       clk = __clk_lookup("aclk_ccore_133");
> +       clk_prepare_enable(clk);

Shouldn't this be rather done before calling
samsung_cmu_register_one()? I don't remember exactly, but wouldn't
clock registration trigger reading back current (mux, div) values from
registers?

Also, do we have any guarantees on order of initialization of
particular CMUs? I believe this will happen in order of DT nodes and
so would be not any kind of guarantee at all.

Best regards,
Tomasz