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

[Shanker Donthineni]

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);


--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
+/**
+ * arm_smccc_get_soc_id_version()
+ *
+ * Returns the SOC ID version.
+ *
+ * When ARM_SMCCC_ARCH_SOC_ID is not present, returns SMCCC_RET_NOT_SUPPORTED.
+ */
+s32 arm_smccc_get_soc_id_version(void);

+/**
+ * arm_smccc_get_soc_id_revision()
+ *
+ * Returns the SOC ID revision.
+ *
+ * When ARM_SMCCC_ARCH_SOC_ID is not present, returns SMCCC_RET_NOT_SUPPORTED.
+ */
+s32 arm_smccc_get_soc_id_revision(void);


2) Use the exported functions in soc_id module.

--- a/drivers/firmware/smccc/soc_id.c
+++ b/drivers/firmware/smccc/soc_id.c
@@ -42,41 +42,23 @@ static int __init smccc_soc_init(void)
        if (arm_smccc_get_version() < ARM_SMCCC_VERSION_1_2)
                return 0;

-       if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE) {
-               pr_err("%s: invalid SMCCC conduit\n", __func__);
-               return -EOPNOTSUPP;
-       }
-
-       arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
-                            ARM_SMCCC_ARCH_SOC_ID, &res);
-
-       if ((int)res.a0 == SMCCC_RET_NOT_SUPPORTED) {
+       soc_id_version = arm_smccc_get_soc_id_version();
+       if (soc_id_version == SMCCC_RET_NOT_SUPPORTED) {
                pr_info("ARCH_SOC_ID not implemented, skipping ....\n");
                return 0;
        }

-       if ((int)res.a0 < 0) {
-               pr_info("ARCH_FEATURES(ARCH_SOC_ID) returned error: %lx\n",
-                       res.a0);
-               return -EINVAL;
-       }
-
-       arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_SOC_ID, 0, &res);
-       if ((int)res.a0 < 0) {
+       if (soc_id_version < 0) {
                pr_err("ARCH_SOC_ID(0) returned error: %lx\n", res.a0);
                return -EINVAL;
        }

-       soc_id_version = res.a0;
-
-       arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_SOC_ID, 1, &res);
-       if ((int)res.a0 < 0) {
+       soc_id_rev = arm_smccc_get_soc_id_revision();
+       if (soc_id_rev < 0) {
                pr_err("ARCH_SOC_ID(1) returned error: %lx\n", res.a0);
                return -EINVAL;
        }

-       soc_id_rev = res.a0;

Kconfig:
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -35,6 +35,7 @@ config ARM_GIC_V3
        select IRQ_DOMAIN_HIERARCHY
        select PARTITION_PERCPU
        select GENERIC_IRQ_EFFECTIVE_AFF_MASK if SMP
+       select HAVE_ARM_SMCCC_DISCOVERY