linux-kernel - Re: [RFC PATCH 2/4] clk: rockchip: rk3399: add ddrc clock support

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Date:	Wed, 1 Jun 2016 08:24:48 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Lin Huang <hl@...k-chips.com>
Cc:	Heiko Stübner <heiko@...ech.de>,
	姚智情 <mark.yao@...k-chips.com>,
	myungjoo.ham@...sung.com,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	linux-clk <linux-clk@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	David Airlie <airlied@...ux.ie>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Derek Basehore <dbasehore@...omium.org>
Subject: Re: [RFC PATCH 2/4] clk: rockchip: rk3399: add ddrc clock support

Lin Huang,

On Wed, Jun 1, 2016 at 2:35 AM, Lin Huang <hl@...k-chips.com> wrote:
> add ddrc clock setting, so we can do ddr frequency
> scaling on rk3399 platform in future.
>
> Signed-off-by: Lin Huang <hl@...k-chips.com>
> ---
>  drivers/clk/rockchip/clk-rk3399.c      | 16 ++++++++++++++++
>  include/dt-bindings/clock/rk3399-cru.h |  1 +
>  2 files changed, 17 insertions(+)
>
> diff --git a/drivers/clk/rockchip/clk-rk3399.c b/drivers/clk/rockchip/clk-rk3399.c
> index f1d8e44..749ea59 100644
> --- a/drivers/clk/rockchip/clk-rk3399.c
> +++ b/drivers/clk/rockchip/clk-rk3399.c
> @@ -118,6 +118,10 @@ PNAME(mux_armclkb_p)                               = { "clk_core_b_lpll_src",
>                                                     "clk_core_b_bpll_src",
>                                                     "clk_core_b_dpll_src",
>                                                     "clk_core_b_gpll_src" };
> +PNAME(mux_ddrclk_p)                            = { "clk_ddrc_lpll_src",
> +                                                   "clk_ddrc_bpll_src",
> +                                                   "clk_ddrc_dpll_src",
> +                                                   "clk_ddrc_gpll_src" };
>  PNAME(mux_aclk_cci_p)                          = { "cpll_aclk_cci_src",
>                                                     "gpll_aclk_cci_src",
>                                                     "npll_aclk_cci_src",
> @@ -1377,6 +1381,18 @@ static struct rockchip_clk_branch rk3399_clk_branches[] __initdata = {
>         COMPOSITE_NOMUX(0, "clk_test", "clk_test_pre", CLK_IGNORE_UNUSED,
>                         RK3368_CLKSEL_CON(58), 0, 5, DFLAGS,
>                         RK3368_CLKGATE_CON(13), 11, GFLAGS),
> +
> +       /* ddrc */
> +       GATE(0, "clk_ddrc_lpll_src", "lpll", CLK_IGNORE_UNUSED,
> +            RK3399_CLKGATE_CON(3), 0, GFLAGS),
> +       GATE(0, "clk_ddrc_bpll_src", "bpll", CLK_IGNORE_UNUSED,
> +            RK3399_CLKGATE_CON(3), 1, GFLAGS),
> +       GATE(0, "clk_ddrc_dpll_src", "dpll", CLK_IGNORE_UNUSED,
> +            RK3399_CLKGATE_CON(3), 2, GFLAGS),
> +       GATE(0, "clk_ddrc_gpll_src", "gpll", CLK_IGNORE_UNUSED,
> +            RK3399_CLKGATE_CON(3), 3, GFLAGS),
> +       COMPOSITE_DDRC(SCLK_DDRCLK, "clk_ddrc", mux_ddrclk_p, CLK_IGNORE_UNUSED,
> +                      RK3399_CLKSEL_CON(6), 4, 2, MFLAGS, 0, 3, DFLAGS),

It seems slightly unfortunate that we need CLK_IGNORE_UNUSED on these.
Only one of these will ever be used at once and it would be awfully
nice if the others could get gated, right?

...presumably this is needed because we might not have an actual
driver for DDR Freq and we definitely want to make sure that clk_ddrc
is enabled in that case.  I guess what we really want is something
like CLK_ENABLE_HAND_OFF eventually, but until then I think you might
get slightly better behavior by getting rid of all of these
CLK_IGNORE_UNUSED and setting "clk_ddrc" as a critical clock, either
using the table in this file or the new flag.

>  };
>
>  static struct rockchip_clk_branch rk3399_clk_pmu_branches[] __initdata = {
> diff --git a/include/dt-bindings/clock/rk3399-cru.h b/include/dt-bindings/clock/rk3399-cru.h
> index 50a44cf..8a0f0442 100644
> --- a/include/dt-bindings/clock/rk3399-cru.h
> +++ b/include/dt-bindings/clock/rk3399-cru.h
> @@ -131,6 +131,7 @@
>  #define SCLK_DPHY_RX0_CFG              165
>  #define SCLK_RMII_SRC                  166
>  #define SCLK_PCIEPHY_REF100M           167
> +#define SCLK_DDRCLK                    168

Almost certainly you'll want to create a separate patch for the
dt-bindings change since it will need to land in a different tree so
it can be pulled into both Heiko's clock topic branch and dts64 topic
branch.



-Doug