rtc: sh: add support for rza series

This same RTC is used in RZ/A series MPUs, therefore with some slight
changes, this driver can be reused. Additionally, since ARM architectures
require Device Tree configurations, device tree support has been added.
Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

drivers/rtc/Kconfig

@@ -1303,10 +1303,10 @@ config RTC_DRV_SA1100
 
 config RTC_DRV_SH
 	tristate "SuperH On-Chip RTC"
-	depends on SUPERH && HAVE_CLK
+	depends on SUPERH || ARCH_RENESAS
 	help
 	  Say Y here to enable support for the on-chip RTC found in
-	  most SuperH processors.
+	  most SuperH processors. This RTC is also found in RZ/A SoCs.
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called rtc-sh.

drivers/rtc/rtc-sh.c

@@ -27,7 +27,15 @@
 #include <linux/log2.h>
 #include <linux/clk.h>
 #include <linux/slab.h>
+#ifdef CONFIG_SUPERH
 #include <asm/rtc.h>
+#else
+/* Default values for RZ/A RTC */
+#define rtc_reg_size		sizeof(u16)
+#define RTC_BIT_INVERTED        0	/* no chip bugs */
+#define RTC_CAP_4_DIGIT_YEAR    (1 << 0)
+#define RTC_DEF_CAPABILITIES    RTC_CAP_4_DIGIT_YEAR
+#endif
 
 #define DRV_NAME	"sh-rtc"
 
@@ -570,6 +578,8 @@ static int __init sh_rtc_probe(struct platform_device *pdev)
 	rtc->alarm_irq = platform_get_irq(pdev, 2);
 
 	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
+	if (!res)
+		res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (unlikely(res == NULL)) {
 		dev_err(&pdev->dev, "No IO resource\n");
 		return -ENOENT;
@@ -587,12 +597,15 @@ static int __init sh_rtc_probe(struct platform_device *pdev)
 	if (unlikely(!rtc->regbase))
 		return -EINVAL;
 
+	if (!pdev->dev.of_node) {
 		clk_id = pdev->id;
 		/* With a single device, the clock id is still "rtc0" */
 		if (clk_id < 0)
 			clk_id = 0;
 
 		snprintf(clk_name, sizeof(clk_name), "rtc%d", clk_id);
+	} else
+		snprintf(clk_name, sizeof(clk_name), "fck");
 
 	rtc->clk = devm_clk_get(&pdev->dev, clk_name);
 	if (IS_ERR(rtc->clk)) {
@@ -608,6 +621,8 @@ static int __init sh_rtc_probe(struct platform_device *pdev)
 	clk_enable(rtc->clk);
 
 	rtc->capabilities = RTC_DEF_CAPABILITIES;
+
+#ifdef CONFIG_SUPERH
 	if (dev_get_platdata(&pdev->dev)) {
 		struct sh_rtc_platform_info *pinfo =
 			dev_get_platdata(&pdev->dev);
@@ -618,6 +633,7 @@ static int __init sh_rtc_probe(struct platform_device *pdev)
 		 */
 		rtc->capabilities |= pinfo->capabilities;
 	}
+#endif
 
 	if (rtc->carry_irq <= 0) {
 		/* register shared periodic/carry/alarm irq */
@@ -738,10 +754,17 @@ static int sh_rtc_resume(struct device *dev)
 
 static SIMPLE_DEV_PM_OPS(sh_rtc_pm_ops, sh_rtc_suspend, sh_rtc_resume);
 
+static const struct of_device_id sh_rtc_of_match[] = {
+	{ .compatible = "renesas,sh-rtc", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, sh_rtc_of_match);
+
 static struct platform_driver sh_rtc_platform_driver = {
 	.driver		= {
 		.name	= DRV_NAME,
 		.pm	= &sh_rtc_pm_ops,
+		.of_match_table = sh_rtc_of_match,
 	},
 	.remove		= __exit_p(sh_rtc_remove),
 };