linux-kernel - [PATCH v1] ACPI: reboot: Increase the delay to avoid racing after writing to ACPI RESET

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Message-Id: <20230607034403.2885-1-james.liu@hpe.com>
Date:   Wed,  7 Jun 2023 11:44:03 +0800
From:   James Liu <james.liu@....com>
To:     rafael@...nel.org, lenb@...nel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     hpelk@...ts.osp.hpe.com, james.liu@....com
Subject: [PATCH v1] ACPI: reboot: Increase the delay to avoid racing after writing to ACPI RESET_REG on AMD Milan platforms.

For AMD Milan platforms, the delay of 15ms is insufficient to avoid racing
of reboot mechanisms. That said, the AMD Milan processors don't reboot
in 15ms after invoking acpi_reset().

The proposed 50ms delay can effectively work around this issue.
This extended delay aligns better with ACPI v6.4 (i.e., sec. 4.8.4.6),
which indicates that ideally OSPM should execute spin loops on the CPUs
in the system following a write to this register.

Signed-off-by: James Liu <james.liu@....com>
---
 drivers/acpi/reboot.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/acpi/reboot.c b/drivers/acpi/reboot.c
index b79b7c99c237..002f7c7814a1 100644
--- a/drivers/acpi/reboot.c
+++ b/drivers/acpi/reboot.c
@@ -78,5 +78,5 @@ void acpi_reboot(void)
 	 * The 15ms delay has been found to be long enough for the system
 	 * to reboot on the affected platforms.
 	 */
-	mdelay(15);
+	mdelay(50);
 }
-- 
2.40.1