On Mon, 2020-10-12 at 12:42 +0200, Rafael J. Wysocki wrote: > On Sat, Oct 10, 2020 at 4:36 AM Zhang Rui <rui.zhang@xxxxxxxxx> > 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@xxxxxxxxx> > > Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx> > > --- > > drivers/acpi/reboot.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/drivers/acpi/reboot.c b/drivers/acpi/reboot.c > > index ca707f5b521d..88e6b083d702 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 +67,10 @@ void acpi_reboot(void) > > acpi_reset(); > > break; > > } > > + > > + /* > > + * delay for 15ms in case the system does not shutdown > > immediately after > > + * writing to the ACPI reset register > > It would also be good to make a note of where the 15ms value comes > from. > > Even if it has been guessed, it will still be good to know that, say, > 5 years from now. > Agreed, patch V2 sent out. -rui > > + */ > > + mdelay(15); > > } > > -- > > 2.17.1 > >
