Re: [edk2][PATCH V1 1/1] ArmPkg: Handle warm reboot request correctly

["Pranav Madhu" <pranav.madhu@arm.com>]

Hi Ard,

Thanks for your suggestions. Please find my reply inline.

Regards,
Pranav

> -----Original Message-----
> From: Ard Biesheuvel <ardb@kernel.org>
> Sent: Thursday, March 10, 2022 8:56 PM
> To: Pranav Madhu <Pranav.Madhu@arm.com>
> Cc: edk2-devel-groups-io <devel@edk2.groups.io>; Ard Biesheuvel
> <ardb+tianocore@kernel.org>; Sami Mujawar <Sami.Mujawar@arm.com>
> Subject: Re: [edk2][PATCH V1 1/1] ArmPkg: Handle warm reboot request
> correctly
> 
> On Thu, 10 Mar 2022 at 14:10, Pranav Madhu <pranav.madhu@arm.com>
> wrote:
> >
> > The warm reboot requests are mapped to cold reboot as the power
> > control module was not capable of handling the warm reboot requests in
> > the legacy implementation. The support for warm reboot support is
> > added into the power control module. To support warm reset, update
> > ArmPsciResetSystemLib, and there by invoke the PSCI call with
> > parameters for warm reboot.
> >
> > Signed-off-by: Pranav Madhu <pranav.madhu@arm.com>
> 
> What happens on 32-bit platforms with this change?

Will change this to PSCI_SYSTEM_RESET2_AARCH32, as this is compatible with AARCH64 as well.

> 
> What happens if the firmware does not implement
> ARM_SMC_ID_PSCI_SYSTEM_RESET2_AARCH64?

As per PSCI 1.1 specification, what I understood is before invoking SYSTEM_RESET2, the OS should query the PSCI capabilities using PSCI_FEATURES for SYSTEM_RESET2 support. The OS should invoke RESET2 only if PSCI_FEATURES returns 0. If the OS is invoking this call without querying the features, PSCI will return UNSUPPORTED.

> 
> > ---
> >  ArmPkg/Include/IndustryStandard/ArmStdSmc.h                  | 1 +
> >  ArmPkg/Library/ArmPsciResetSystemLib/ArmPsciResetSystemLib.c | 7
> > +++++--
> >  2 files changed, 6 insertions(+), 2 deletions(-)
> >
> > Link to github branch for this patch -
> > https://github.com/Pranav-Madhu/edk2/tree/topics/warm_reboot
> >
> > diff --git a/ArmPkg/Include/IndustryStandard/ArmStdSmc.h
> > b/ArmPkg/Include/IndustryStandard/ArmStdSmc.h
> > index 655edc21b205..c9059dead6e9 100644
> > --- a/ArmPkg/Include/IndustryStandard/ArmStdSmc.h
> > +++ b/ArmPkg/Include/IndustryStandard/ArmStdSmc.h
> > @@ -93,6 +93,7 @@
> >  #define ARM_SMC_ID_PSCI_MIGRATE_AARCH32        0x84000005
> >  #define ARM_SMC_ID_PSCI_SYSTEM_OFF             0x84000008
> >  #define ARM_SMC_ID_PSCI_SYSTEM_RESET           0x84000009
> > +#define ARM_SMC_ID_PSCI_SYSTEM_RESET2_AARCH64  0xc4000012
> >
> >  /* The current PSCI version is:  0.2 */  #define
> > ARM_SMC_PSCI_VERSION_MAJOR  0 diff --git
> > a/ArmPkg/Library/ArmPsciResetSystemLib/ArmPsciResetSystemLib.c
> > b/ArmPkg/Library/ArmPsciResetSystemLib/ArmPsciResetSystemLib.c
> > index 7bcd34849507..27e048ba0f7a 100644
> > --- a/ArmPkg/Library/ArmPsciResetSystemLib/ArmPsciResetSystemLib.c
> > +++ b/ArmPkg/Library/ArmPsciResetSystemLib/ArmPsciResetSystemLib.c
> > @@ -45,10 +45,13 @@ LibResetSystem (
> >    ARM_SMC_ARGS  ArmSmcArgs;
> >
> >    switch (ResetType) {
> > +    case EfiResetWarm:
> > +      ArmSmcArgs.Arg0 = ARM_SMC_ID_PSCI_SYSTEM_RESET2_AARCH64;
> > +      ArmSmcArgs.Arg1 = 0;
> > +      ArmSmcArgs.Arg2 = 0;
> > +      break;
> >      case EfiResetPlatformSpecific:
> >      // Map the platform specific reset as reboot
> > -    case EfiResetWarm:
> > -    // Map a warm reset into a cold reset
> >      case EfiResetCold:
> >        // Send a PSCI 0.2 SYSTEM_RESET command
> >        ArmSmcArgs.Arg0 = ARM_SMC_ID_PSCI_SYSTEM_RESET;
> > --
> > 2.17.1
> >