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

From: hl
Date: Wed Jun 01 2016 - 21:32:55 EST

Hi Doug&Heiko,

On 2016å06æ01æ 23:46, Heiko StÃbner wrote:
Am Mittwoch, 1. Juni 2016, 08:24:48 schrieb Doug Anderson:
Lin Huang,

On Wed, Jun 1, 2016 at 2:35 AM, Lin Huang <hl@xxxxxxxxxxxxxx> wrote:
add ddrc clock setting, so we can do ddr frequency
scaling on rk3399 platform in future.

Signed-off-by: Lin Huang <hl@xxxxxxxxxxxxxx>

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",>

+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",

@@ -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,
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.
My current feeling is that staying with the homegrown solution for critical
clocks might be preferable until the clk-handoff mechanism lands as well, as
our critical clocks fall into both categories and I'd like to not touch
everything twice.

The clock above should be controlled by the dcf, so falls into the handoff
category (critical until a driver picks up the clock).

Also mixing both new and old approach might get confusing.

But I'm definitly open to counter-arguments :-)
I will remove CLK_IGNORE_UNUSED flag and set
"clk_ddrc" as critical clock in next version. Besides, i think we should also
set "clk_ddrc_dpll_src" as critical clock, since we always use dpll as ddr clock source,
and it should always on.

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
will fix next version, thanks.

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