Re: [edk2-devel] [PATCH 3/4] UefiCpuPkg/CpuTimerDxeRiscV64: Add support for Sstc

["Sunil V L" <sunilvl@ventanamicro.com>]

On Thu, Jan 04, 2024 at 03:38:17PM +0100, Laszlo Ersek wrote:
> On 1/3/24 14:58, Sunil V L wrote:
> > Sstc extension allows to program the timer and receive the interrupt
> > without using an SBI call. This reduces the latency to generate the timer
> > interrupt. So, detect whether Sstc extension is supported and use the
> > stimecmp register directly to program the timer interrupt.
> > 
> > Cc: Gerd Hoffmann <kraxel@redhat.com>
> > Cc: Rahul Kumar <rahul1.kumar@intel.com>
> > Cc: Laszlo Ersek <lersek@redhat.com>
> > Cc: Ray Ni <ray.ni@intel.com>
> > Cc: Andrei Warkentin <andrei.warkentin@intel.com>
> > Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
> > ---
> >  .../CpuTimerDxeRiscV64/CpuTimerDxeRiscV64.inf |  1 +
> >  UefiCpuPkg/CpuTimerDxeRiscV64/Timer.h         |  2 ++
> >  UefiCpuPkg/CpuTimerDxeRiscV64/Timer.c         | 30 +++++++++++++++++--
> >  3 files changed, 31 insertions(+), 2 deletions(-)
> > 
> > diff --git a/UefiCpuPkg/CpuTimerDxeRiscV64/CpuTimerDxeRiscV64.inf b/UefiCpuPkg/CpuTimerDxeRiscV64/CpuTimerDxeRiscV64.inf
> > index aba660186dc0..f2a2cf12caef 100644
> > --- a/UefiCpuPkg/CpuTimerDxeRiscV64/CpuTimerDxeRiscV64.inf
> > +++ b/UefiCpuPkg/CpuTimerDxeRiscV64/CpuTimerDxeRiscV64.inf
> > @@ -41,6 +41,7 @@ [Sources.RISCV64]
> >    Timer.c
> >  
> >  [Pcd]
> > +  gEfiMdePkgTokenSpaceGuid.PcdRiscVFeatureOverride           ## CONSUMES
> >    gUefiCpuPkgTokenSpaceGuid.PcdCpuCoreCrystalClockFrequency  ## CONSUMES
> >  
> >  [Protocols]
> > diff --git a/UefiCpuPkg/CpuTimerDxeRiscV64/Timer.h b/UefiCpuPkg/CpuTimerDxeRiscV64/Timer.h
> > index 9b3542230cb5..5e5071b3f0b2 100644
> > --- a/UefiCpuPkg/CpuTimerDxeRiscV64/Timer.h
> > +++ b/UefiCpuPkg/CpuTimerDxeRiscV64/Timer.h
> > @@ -26,6 +26,8 @@
> >  //
> >  #define DEFAULT_TIMER_TICK_DURATION  100000
> >  
> > +#define RISCV_CPU_FEATURE_SSTC_BITMASK  0x2
> 
> (1) Not a bug by any means, but BIT1 might read more idiomatic.
> 
I misunderstood your comment. Will use BIT1 instead of 0x2.

Thanks!
Sunil


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