Re: [PATCH v3 5/6] ARM: shmobile: lager: Set clock rates for SDHI

On Mon, 2015-06-29 at 06:23 +0000, Kuninori Morimoto wrote:

Hi Ben 
Cc Laurent, Geert, Magnus

quoted

diff --git a/arch/arm/boot/dts/r8a7790-lager.dts b/arch/arm/boot/dts/r8a7790-lager.dts
index aaa4f258e279..5f68e53c58ae 100644
--- a/arch/arm/boot/dts/r8a7790-lager.dts
+++ b/arch/arm/boot/dts/r8a7790-lager.dts

@@ -488,6 +488,9 @@
 	pinctrl-0 = <&sdhi0_pins>;
 	pinctrl-names = "default";
 
+	assigned-clocks = <&mstp3_clks R8A7790_CLK_SDHI0>;
+	assigned-clock-rates = <156000000>;
+
 	vmmc-supply = <&vcc_sdhi0>;
 	vqmmc-supply = <&vccq_sdhi0>;
 	cd-gpios = <&gpio3 6 GPIO_ACTIVE_LOW>;

@@ -498,6 +501,9 @@
 	pinctrl-0 = <&sdhi2_pins>;
 	pinctrl-names = "default";
 
+	assigned-clocks = <&mstp3_clks R8A7790_CLK_SDHI2>;
+	assigned-clock-rates = <97500000>;
+
 	vmmc-supply = <&vcc_sdhi2>;
 	vqmmc-supply = <&vccq_sdhi2>;
 	cd-gpios = <&gpio3 22 GPIO_ACTIVE_LOW>;

Thank you for your patch, but I still wandering about this.
Please correct me if I'm misunderstanding.

Above seetings is for SDHI IP, and it can divide it ?
The image is

	[CPG] -> 156 MHz -> [SDHI] -> 1/x -> [CARD]
	         ~~~~~~~

If so, why we can't use max-frequency ?
We can calculate/set SDHI IP clocks via 
max-frequency / clk_round_rate() / clk_set_rate()
since we know SDHI's divider capability.

SH-MMC is using this style. and I think it is flexible for every speed.
Please check sh_mmcif_clock_control(), sh_mmcif_clk_setup()
on ${LINUX}/drivers/mmc/host/sh_mmcif.c

That's certainly a nicer way of doing this.  The difficulty I see is
that tmio_mmc doesn't know anything about the input clock, and not all
of the drivers using it actually use the clock framework.

Ben.