rtc: efi: Enable SET/GET WAKEUP services as optional

The current implementation of rtc-efi is expecting all the 4
time services GET{SET}_TIME{WAKEUP} must be supported by UEFI
firmware. As per the EFI_RT_PROPERTIES_TABLE, the platform
specific implementations can choose to enable selective time
services based on the RTC device capabilities.

This patch does the following changes to provide GET/SET RTC
services on platforms that do not support the WAKEUP feature.

1) Relax time services cap check when creating a platform device.
2) Clear RTC_FEATURE_ALARM bit in the absence of WAKEUP services.
3) Conditional alarm entries in '/proc/driver/rtc'.

Cc: <stable@vger.kernel.org> # v6.0+
Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
Link: https://lore.kernel.org/r/20230102230630.192911-1-sdonthineni@nvidia.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/rtc-efi.c

@@ -188,9 +188,10 @@ static int efi_set_time(struct device *dev, struct rtc_time *tm)
 
 static int efi_procfs(struct device *dev, struct seq_file *seq)
 {
-	efi_time_t      eft, alm;
-	efi_time_cap_t  cap;
-	efi_bool_t      enabled, pending;
+	efi_time_t        eft, alm;
+	efi_time_cap_t    cap;
+	efi_bool_t        enabled, pending;
+	struct rtc_device *rtc = dev_get_drvdata(dev);
 
 	memset(&eft, 0, sizeof(eft));
 	memset(&alm, 0, sizeof(alm));
@@ -213,23 +214,25 @@ static int efi_procfs(struct device *dev, struct seq_file *seq)
 		/* XXX fixme: convert to string? */
 		seq_printf(seq, "Timezone\t: %u\n", eft.timezone);
 
-	seq_printf(seq,
-		   "Alarm Time\t: %u:%u:%u.%09u\n"
-		   "Alarm Date\t: %u-%u-%u\n"
-		   "Alarm Daylight\t: %u\n"
-		   "Enabled\t\t: %s\n"
-		   "Pending\t\t: %s\n",
-		   alm.hour, alm.minute, alm.second, alm.nanosecond,
-		   alm.year, alm.month, alm.day,
-		   alm.daylight,
-		   enabled == 1 ? "yes" : "no",
-		   pending == 1 ? "yes" : "no");
-
-	if (eft.timezone == EFI_UNSPECIFIED_TIMEZONE)
-		seq_puts(seq, "Timezone\t: unspecified\n");
-	else
-		/* XXX fixme: convert to string? */
-		seq_printf(seq, "Timezone\t: %u\n", alm.timezone);
+	if (test_bit(RTC_FEATURE_ALARM, rtc->features)) {
+		seq_printf(seq,
+			   "Alarm Time\t: %u:%u:%u.%09u\n"
+			   "Alarm Date\t: %u-%u-%u\n"
+			   "Alarm Daylight\t: %u\n"
+			   "Enabled\t\t: %s\n"
+			   "Pending\t\t: %s\n",
+			   alm.hour, alm.minute, alm.second, alm.nanosecond,
+			   alm.year, alm.month, alm.day,
+			   alm.daylight,
+			   enabled == 1 ? "yes" : "no",
+			   pending == 1 ? "yes" : "no");
+
+		if (eft.timezone == EFI_UNSPECIFIED_TIMEZONE)
+			seq_puts(seq, "Timezone\t: unspecified\n");
+		else
+			/* XXX fixme: convert to string? */
+			seq_printf(seq, "Timezone\t: %u\n", alm.timezone);
+	}
 
 	/*
 	 * now prints the capabilities
@@ -269,7 +272,10 @@ static int __init efi_rtc_probe(struct platform_device *dev)
 
 	rtc->ops = &efi_rtc_ops;
 	clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, rtc->features);
-	set_bit(RTC_FEATURE_ALARM_WAKEUP_ONLY, rtc->features);
+	if (efi_rt_services_supported(EFI_RT_SUPPORTED_WAKEUP_SERVICES))
+		set_bit(RTC_FEATURE_ALARM_WAKEUP_ONLY, rtc->features);
+	else
+		clear_bit(RTC_FEATURE_ALARM, rtc->features);
 
 	device_init_wakeup(&dev->dev, true);
 

include/linux/efi.h

@@ -668,7 +668,8 @@ extern struct efi {
 
 #define EFI_RT_SUPPORTED_ALL					0x3fff
 
-#define EFI_RT_SUPPORTED_TIME_SERVICES				0x000f
+#define EFI_RT_SUPPORTED_TIME_SERVICES				0x0003
+#define EFI_RT_SUPPORTED_WAKEUP_SERVICES			0x000c
 #define EFI_RT_SUPPORTED_VARIABLE_SERVICES			0x0070
 
 extern struct mm_struct efi_mm;