On Wed, Jun 07, 2023 at 01:19:42PM +0200, Rafael J. Wysocki wrote: > On Wed, Jun 7, 2023 at 5:44 AM James Liu <james.liu@xxxxxxx> wrote: > > > > 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@xxxxxxx> > > Why do you want to affect everyone (including guest kernels running in > virtual machines AFAICS) in order to address a problem specific to one > platform? I hoped to address this issue for any platform requiring a longer delay to complete ACPI reset in time for any (maybe silicon-level) reasons. Some AMD Milan platforms were the cases that we've found so far. Except that, since ACPI spec indicates there should be a spin loop (long enough) after the write instruction to Reset Register, I thought it should be no harms to the other systems which well consider this spin loop when they claim to support ACPI reboot. Btw, I am just curious, why is the virtual machine mentioned here? is the 50ms delay in acpi_reboot() for a guest OS on VM so long that some unexpected behavior might happen? > Wouldn't it be better to quirk that platform and document the quirk properly? Yeah, it could be. Actually we considered this, and we will consider it again. > > --- > > 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 > >
