* [PATCH V2] acpi: reboot: fix racing after writing to ACPI RESET_REG
@ 2020-10-13 7:35 Zhang Rui
2020-10-16 16:06 ` Rafael J. Wysocki
0 siblings, 1 reply; 2+ messages in thread
From: Zhang Rui @ 2020-10-13 7:35 UTC (permalink / raw)
To: linux-acpi, rjw; +Cc: sukumar.ghorai, rui.zhang
According to the ACPI spec, "The system must reset immediately following
the write to the ACPI RESET_REG register.", but there are cases that the
system does not follow this and results in racing with the subsequetial
reboot mechanism, which brings unexpected behavior.
Fix this by adding a 15ms delay after writing to the ACPI RESET_REG.
Reported-by: Ghorai, Sukumar <sukumar.ghorai@intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
---
drivers/acpi/reboot.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/acpi/reboot.c b/drivers/acpi/reboot.c
index ca707f5b521d..0e357cb5612f 100644
--- a/drivers/acpi/reboot.c
+++ b/drivers/acpi/reboot.c
@@ -3,6 +3,7 @@
#include <linux/pci.h>
#include <linux/acpi.h>
#include <acpi/reboot.h>
+#include <linux/delay.h>
#ifdef CONFIG_PCI
static void acpi_pci_reboot(struct acpi_generic_address *rr, u8 reset_value)
@@ -66,4 +67,13 @@ void acpi_reboot(void)
acpi_reset();
break;
}
+
+ /*
+ * Some platforms do not shutdown immediately after writing to the
+ * ACPI reset register, and this results in racing with the
+ * subsequetial reboot mechanism.
+ * Delay for 15ms has been proved to be long enough for the system
+ * to reboot, for these platforms.
+ */
+ mdelay(15);
}
--
2.17.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH V2] acpi: reboot: fix racing after writing to ACPI RESET_REG
2020-10-13 7:35 [PATCH V2] acpi: reboot: fix racing after writing to ACPI RESET_REG Zhang Rui
@ 2020-10-16 16:06 ` Rafael J. Wysocki
0 siblings, 0 replies; 2+ messages in thread
From: Rafael J. Wysocki @ 2020-10-16 16:06 UTC (permalink / raw)
To: Zhang Rui; +Cc: ACPI Devel Maling List, Rafael J. Wysocki, sukumar.ghorai
On Tue, Oct 13, 2020 at 9:36 AM Zhang Rui <rui.zhang@intel.com> wrote:
>
> According to the ACPI spec, "The system must reset immediately following
> the write to the ACPI RESET_REG register.", but there are cases that the
> system does not follow this and results in racing with the subsequetial
> reboot mechanism, which brings unexpected behavior.
>
> Fix this by adding a 15ms delay after writing to the ACPI RESET_REG.
>
> Reported-by: Ghorai, Sukumar <sukumar.ghorai@intel.com>
> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> ---
> drivers/acpi/reboot.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/acpi/reboot.c b/drivers/acpi/reboot.c
> index ca707f5b521d..0e357cb5612f 100644
> --- a/drivers/acpi/reboot.c
> +++ b/drivers/acpi/reboot.c
> @@ -3,6 +3,7 @@
> #include <linux/pci.h>
> #include <linux/acpi.h>
> #include <acpi/reboot.h>
> +#include <linux/delay.h>
>
> #ifdef CONFIG_PCI
> static void acpi_pci_reboot(struct acpi_generic_address *rr, u8 reset_value)
> @@ -66,4 +67,13 @@ void acpi_reboot(void)
> acpi_reset();
> break;
> }
> +
> + /*
> + * Some platforms do not shutdown immediately after writing to the
> + * ACPI reset register, and this results in racing with the
> + * subsequetial reboot mechanism.
> + * Delay for 15ms has been proved to be long enough for the system
> + * to reboot, for these platforms.
> + */
> + mdelay(15);
> }
> --
Applied as 5.10-rc material with some edits in the comment above and subject.
Thanks!
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