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. > + */ > + mdelay(15); > } > -- > 2.17.1 >
