rtc: renesas-rtca3: Add driver for RTCA-3 available on Renesas RZ/G3S SoC

The RTC IP (RTCA-3) available on the Renesas RZ/G3S SoC has calendar count
mode and binary count mode (selectable though RCR2.CNTMD) capabilities,
alarm capabilities, clock error correction capabilities. It can generate
alarm, period, carry interrupts.

Add a driver for RTCA-3 IP. The driver implements calendar count mode (as
the conversion b/w RTC and system time is simpler, done with bcd2bin(),
bin2bcd()), read and set time, read and set alarm, read and set
an offset.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Link: https://lore.kernel.org/r/20241030110120.332802-6-claudiu.beznea.uj@bp.renesas.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Author: claudiubeznea

MAINTAINERS

@@ -19721,6 +19721,14 @@ S:	Supported
 F:	Documentation/devicetree/bindings/timer/renesas,rz-mtu3.yaml
 F:	drivers/counter/rz-mtu3-cnt.c
 
+RENESAS RTCA-3 RTC DRIVER
+M:	Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
+L:	linux-rtc@vger.kernel.org
+L:	linux-renesas-soc@vger.kernel.org
+S:	Supported
+F:	Documentation/devicetree/bindings/rtc/renesas,rz-rtca3.yaml
+F:	drivers/rtc/rtc-renesas-rtca3.c
+
 RENESAS RZ/N1 A5PSW SWITCH DRIVER
 M:	Clément Léger <clement.leger@bootlin.com>
 L:	linux-renesas-soc@vger.kernel.org

drivers/rtc/Kconfig

@@ -2005,6 +2005,16 @@ config RTC_DRV_MA35D1
 	   This driver can also be built as a module, if so, the module
 	   will be called "rtc-ma35d1".
 
+config RTC_DRV_RENESAS_RTCA3
+	tristate "Renesas RTCA-3 RTC"
+	depends on ARCH_RENESAS
+	help
+	  If you say yes here you get support for the Renesas RTCA-3 RTC
+	  available on the Renesas RZ/G3S SoC.
+
+	  This driver can also be built as a module, if so, the module
+	  will be called "rtc-rtca3".
+
 comment "HID Sensor RTC drivers"
 
 config RTC_DRV_HID_SENSOR_TIME

drivers/rtc/Makefile

@@ -158,6 +158,7 @@ obj-$(CONFIG_RTC_DRV_RX8025)	+= rtc-rx8025.o
 obj-$(CONFIG_RTC_DRV_RX8111)	+= rtc-rx8111.o
 obj-$(CONFIG_RTC_DRV_RX8581)	+= rtc-rx8581.o
 obj-$(CONFIG_RTC_DRV_RZN1)	+= rtc-rzn1.o
+obj-$(CONFIG_RTC_DRV_RENESAS_RTCA3)	+= rtc-renesas-rtca3.o
 obj-$(CONFIG_RTC_DRV_S35390A)	+= rtc-s35390a.o
 obj-$(CONFIG_RTC_DRV_S3C)	+= rtc-s3c.o
 obj-$(CONFIG_RTC_DRV_S5M)	+= rtc-s5m.o