linux-kernel - [PATCH] efi: remove the rtc-wakeup capability from default value

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Message-Id: <20250709103541.7268-1-feng.tang@linux.alibaba.com>
Date: Wed,  9 Jul 2025 18:35:41 +0800
From: Feng Tang <feng.tang@...ux.alibaba.com>
To: Ard Biesheuvel <ardb@...nel.org>,
	linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Feng Tang <feng.tang@...ux.alibaba.com>
Subject: [PATCH] efi:  remove the rtc-wakeup capability from default value

The kernel selftest of rtc reported a error on an ARM server:

	RUN           rtc.alarm_alm_set ...
	rtctest.c:262:alarm_alm_set:Alarm time now set to 17:31:36.
	rtctest.c:267:alarm_alm_set:Expected -1 (-1) != rc (-1)
	alarm_alm_set: Test terminated by assertion
		 FAIL  rtc.alarm_alm_set
	not ok 5 rtc.alarm_alm_set

The root cause is, the unerlying EFI firmware doesn't support wakeup
service (get/set alarm), while it doesn't have the efi 'RT_PROP'
table either. The current code logic will claim efi supports these
runtime service capability by default, and let following 'RT_PROP'
table parsing to correct it, if that table exists.

This issue was reproduced on ARM server from another verndor, and not
reproudce on one x86 server (Icelake). All these 3 platforms don't have
'RT_PROP' tables, so they are all claimed to support alarm service,
but x86 server uses real CMOS RTC device instead rtc-efi device, and
passes the test.

So remove the wakeup/alarm capability from default value, and setup
the capability bits according to the 'RT_PROP' table parsing.

Signed-off-by: Feng Tang <feng.tang@...ux.alibaba.com>
---
 drivers/firmware/efi/efi.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index e57bff702b5f..7cf35376a2f7 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -789,6 +789,17 @@ int __init efi_config_parse_tables(const efi_config_table_t *config_tables,
 		}
 	}

+	/*
+	 * After bootup, the runtime_supported_mask was set to be capable of
+	 * all features, which could be kind of too optimistici. In real
+	 * world, many platforms don't support advanced RTC wakeup runtime
+	 * service, while they don't provide RT_PROPERTY table either, which
+	 * led to rtc-wakeup capability being worngly claimed.
+	 *
+	 * So remove the wakeup capbility from default value, and let the
+	 * RT_PROPERTY do the judge.
+	 */
+	efi.runtime_supported_mask &= ~EFI_RT_SUPPORTED_WAKEUP_SERVICES;
 	if (rt_prop != EFI_INVALID_TABLE_ADDR) {
 		efi_rt_properties_table_t *tbl;

-- 
2.43.5