clk: Add RISC-V Canaan Kendryte K210 clock driver

Add a clock provider driver for the Canaan Kendryte K210 RISC-V SoC.
This new driver with the compatible string "canaan,k210-clk" implements
support for the full clock structure of the K210 SoC. Since it is
required for the correct operation of the SoC, this driver is
selected by default for compilation when the SOC_CANAAN option is
selected.

With this change, the k210-sysctl driver is turned into a simple
platform driver which enables its power bus clock and triggers
populating its child nodes. The sysctl driver retains the SOC early
initialization code, but the implementation now relies on the new
function k210_clk_early_init() provided by the new clk-k210 driver.

The clock structure implemented and many of the coding ideas for the
driver come from the work by Sean Anderson on the K210 support for the
U-Boot project.

Cc: Stephen Boyd <[email protected]>
Cc: Michael Turquette <[email protected]>
Cc: [email protected]
Signed-off-by: Damien Le Moal <[email protected]>
Reviewed-by: Stephen Boyd <[email protected]>
Signed-off-by: Palmer Dabbelt <[email protected]>

drivers/clk/Kconfig

@@ -368,6 +368,13 @@ config COMMON_CLK_FIXED_MMIO
 	help
 	  Support for Memory Mapped IO Fixed clocks
 
+config COMMON_CLK_K210
+	bool "Clock driver for the Canaan Kendryte K210 SoC"
+	depends on OF && RISCV && SOC_CANAAN
+	default SOC_CANAAN
+	help
+	  Support for the Canaan Kendryte K210 RISC-V SoC clocks.
+
 source "drivers/clk/actions/Kconfig"
 source "drivers/clk/analogbits/Kconfig"
 source "drivers/clk/baikal-t1/Kconfig"

drivers/clk/Makefile

@@ -37,6 +37,7 @@ obj-$(CONFIG_COMMON_CLK_ASPEED)		+= clk-aspeed.o
 obj-$(CONFIG_MACH_ASPEED_G6)		+= clk-ast2600.o
 obj-$(CONFIG_ARCH_HIGHBANK)		+= clk-highbank.o
 obj-$(CONFIG_CLK_HSDK)			+= clk-hsdk-pll.o
+obj-$(CONFIG_COMMON_CLK_K210)		+= clk-k210.o
 obj-$(CONFIG_COMMON_CLK_LOCHNAGAR)	+= clk-lochnagar.o
 obj-$(CONFIG_COMMON_CLK_MAX77686)	+= clk-max77686.o
 obj-$(CONFIG_COMMON_CLK_MAX9485)	+= clk-max9485.o