Re: [PATCH v2] irqchip/gicv3: Workaround for NVIDIA erratum T241-FABRIC-4

[Marc Zyngier]

On 2023-03-16 15:10, Sudeep Holla wrote:
> On Wed, Mar 15, 2023 at 07:27:14AM -0500, Shanker Donthineni wrote:
> > Hi Marc,
> >
> > On 3/15/23 03:34, Marc Zyngier wrote:
> > > Please don't duplicate existing code. There is already the required
> > > infrastructure in drivers/firmware/smccc/soc_id.c. All you need to do
> > > is:
> > >
> > > - disassociate the SMCCC probing from the device registration
> > >
> > > - probe the SOC_ID early
> > >
> > > - add accessors for the relevant data
> > >
> > > - select ARM_SMCCC_SOD_ID/ARM_SMCCC_DISCOVERY from the GICv3 Kconfig
> >
> >
> > I have not modified soc_id.c as it expects to be loaded as a module 
> > with
> > the use of module_init() and module_exit() functions. The exported 
> > symbols
> > in soc_id driver cannot be accessed from the built-in code.
> >
> > Agree, the SOD-ID discovery code was duplicated.
> >
> > Please guide me if the below approach is okay?
> >
> > 1) Probe the SOC-ID in arm_smccc_version_init() and export two 
> > functions
> > arm_smccc_get_soc_id_version() and arm_smccc_get_soc_id_revision().
> >
> > --- a/drivers/firmware/smccc/smccc.c
> > +++ b/drivers/firmware/smccc/smccc.c
> > @@ -17,9 +17,13 @@ static enum arm_smccc_conduit smccc_conduit = 
> > SMCCC_CONDUIT_NONE;
> >
> >  bool __ro_after_init smccc_trng_available = false;
> >  u64 __ro_after_init smccc_has_sve_hint = false;
> > +s32 __ro_after_init smccc_soc_id_version = SMCCC_RET_NOT_SUPPORTED;
> > +s32 __ro_after_init smccc_soc_id_revision = SMCCC_RET_NOT_SUPPORTED;
> >
> >  void __init arm_smccc_version_init(u32 version, enum 
> > arm_smccc_conduit conduit)
> >  {
> > +       struct arm_smccc_res res;
> > +
> >         smccc_version = version;
> >         smccc_conduit = conduit;
> >
> > @@ -27,6 +31,18 @@ void __init arm_smccc_version_init(u32 version, 
> > enum arm_smccc_conduit conduit)
> >         if (IS_ENABLED(CONFIG_ARM64_SVE) &&
> >             smccc_version >= ARM_SMCCC_VERSION_1_3)
> >                 smccc_has_sve_hint = true;
> > +
> > +       if ((smccc_version >= ARM_SMCCC_VERSION_1_2) &&
> > +           (smccc_conduit != SMCCC_CONDUIT_NONE)) {
> > +               arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
> > +                                    ARM_SMCCC_ARCH_SOC_ID, &res);
> > +               if ((s32)res.a0 >= 0) {
> > +                       arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_SOC_ID, 0, 
> > &res);
> > +                       smccc_soc_id_version = (s32)res.a0;
> > +                       arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_SOC_ID, 1, 
> > &res);
> > +                       smccc_soc_id_revision = (s32)res.a0;
> > +               }
> > +       }
> >  }
> >
> >
> > +s32 arm_smccc_get_soc_id_version(void)
> > +{
> > +       return smccc_soc_id_version;
> > +}
> > +EXPORT_SYMBOL_GPL(arm_smccc_get_soc_id_version);
> > +
> > +s32 arm_smccc_get_soc_id_revision(void)
> > +{
> > +       return smccc_soc_id_revision;
> > +}
> > +EXPORT_SYMBOL_GPL(arm_smccc_get_soc_id_revision);
>
> Overall, it looks OK to me. However I see neither the gic nor the 
> soc_id
> can be build as module atm. So do we really need the export symbols if 
> no
> other modules are using it ?

It really shouldn't be exported. Having accessors should be enough.

Thanks,

        M.
--
Jazz is not dead. It just smells funny...