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

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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...



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