clk: wpcm450: Add Nuvoton WPCM450 clock/reset controller driver

This driver implements the following features w.r.t. the clock and reset
controller in the WPCM450 SoC:

- It calculates the rates for all clocks managed by the clock controller
- It leaves the clock tree mostly unchanged, except that it enables/
  disables clock gates based on usage.
- It exposes the reset lines managed by the controller using the
  Generic Reset Controller subsystem

NOTE: If the driver and the corresponding devicetree node are present,
      the driver will disable "unused" clocks. This is problem until
      the clock relations are properly declared in the devicetree (in a
      later patch). Until then, the clk_ignore_unused kernel parameter
      can be used as a workaround.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-by: Joel Stanley <joel@jms.id.au>
---

I have considered converting this driver to a platform driver instead of
using CLK_OF_DECLARE, because platform drivers are generally the way
forward. However, the timer-npcm7xx driver used on the same platform
requires is initialized with TIMER_OF_DECLARE and thus requires the
clocks to be available earlier than a platform driver can provide them.


v9:
- Apply comments made by Stephen Boyd
- Move to drivers/clk/nuvoton/ directory
- Update SPDX license identifier from GPL-2.0 to GPL-2.0-only
- Rename clk_np variable to np
- Use of_clk_hw_register
- Refer to clock parents by .fw_name

v8:
- https://lore.kernel.org/lkml/20230428190226.1304326-3-j.neuschaefer@gmx.net/
- Use %pe format specifier throughout the driver, as suggested by Philipp Zabel
- Add Joel's R-b

v7:
- https://lore.kernel.org/lkml/20230422220240.322572-3-j.neuschaefer@gmx.net/
- Simplify error handling by not deallocating resources

v6:
- Enable RESET_SIMPLE based on ARCH_WPCM450, not ARCH_NPCM, as suggested by Tomer Maimon

v5:
- https://lore.kernel.org/lkml/20221104161850.2889894-6-j.neuschaefer@gmx.net/
- Switch to using clk_parent_data

v4:
- Fix reset controller initialization

v3:
- Change reference clock name from "refclk" to "ref"
- Remove unused variable in return path of wpcm450_clk_register_pll
- Remove unused divisor tables

v2:
- no changes

drivers/clk/Makefile

@@ -106,7 +106,7 @@ endif
 obj-y					+= mstar/
 obj-y					+= mvebu/
 obj-$(CONFIG_ARCH_MXS)			+= mxs/
-obj-$(CONFIG_ARCH_MA35)			+= nuvoton/
+obj-y					+= nuvoton/
 obj-$(CONFIG_COMMON_CLK_NXP)		+= nxp/
 obj-$(CONFIG_COMMON_CLK_PISTACHIO)	+= pistachio/
 obj-$(CONFIG_COMMON_CLK_PXA)		+= pxa/

drivers/clk/nuvoton/Kconfig

@@ -3,7 +3,7 @@
 
 config COMMON_CLK_NUVOTON
 	bool "Nuvoton clock controller common support"
-	depends on ARCH_MA35 || COMPILE_TEST
+	depends on ARCH_MA35 || ARCH_NPCM || COMPILE_TEST
 	default y
 	help
 	  Say y here to enable common clock controller for Nuvoton platforms.
@@ -16,4 +16,10 @@ config CLK_MA35D1
 	help
 	  Build the clock controller driver for MA35D1 SoC.
 
+config CLK_WPCM450
+	bool "Nuvoton WPCM450 clock/reset controller support"
+	default y
+	help
+	  Build the clock and reset controller driver for the WPCM450 SoC.
+
 endif

drivers/clk/nuvoton/Makefile

@@ -2,3 +2,4 @@
 obj-$(CONFIG_CLK_MA35D1) += clk-ma35d1.o
 obj-$(CONFIG_CLK_MA35D1) += clk-ma35d1-divider.o
 obj-$(CONFIG_CLK_MA35D1) += clk-ma35d1-pll.o
+obj-$(CONFIG_CLK_WPCM450) += clk-wpcm450.o