rtc: m68k: provide ioctl for q40

The q40 platform is the only machine in the kernel that provides
RTC_PLL_GET/RTC_PLL_SET ioctl commands in its rtc through the
mach_get_rtc_pll/mach_set_rtc_pll callbacks.

However, this currenctly works only in the old-style genrtc
driver, not the (somewhat) modern rtc-generic driver replacing
it. This adds an ioctl implementation to the m68k generic_rtc_ops
in order to let both drivers provide the same API.

After this, we should be able to remove support for genrtc
from the m68k architecture.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

arch/m68k/kernel/time.c

@@ -100,7 +100,32 @@ static int rtc_generic_set_time(struct device *dev, struct rtc_time *tm)
 	return 0;
 }
 
+static int rtc_ioctl(struct device *dev, unsigned int cmd, unsigned long arg)
+{
+	struct rtc_pll_info pll;
+	struct rtc_pll_info __user *argp = (void __user *)arg;
+
+	switch (cmd) {
+	case RTC_PLL_GET:
+		if (!mach_get_rtc_pll || mach_get_rtc_pll(&pll))
+			return -EINVAL;
+		return copy_to_user(argp, &pll, sizeof pll) ? -EFAULT : 0;
+
+	case RTC_PLL_SET:
+		if (!mach_set_rtc_pll)
+			return -EINVAL;
+		if (!capable(CAP_SYS_TIME))
+			return -EACCES;
+		if (copy_from_user(&pll, argp, sizeof(pll)))
+			return -EFAULT;
+		return mach_set_rtc_pll(&pll);
+	}
+
+	return -ENOIOCTLCMD;
+}
+
 static const struct rtc_class_ops generic_rtc_ops = {
+	.ioctl = rtc_ioctl,
 	.read_time = rtc_generic_get_time,
 	.set_time = rtc_generic_set_time,
 };