[Xen-devel] [PATCH v2 09/15] xen/arm: psci: Detect SMCCC version

[Julien Grall <julien.grall@xxxxxxx>]

PSCI 1.0 and later allows the SMCCC version to be (indirectly) probed
via PSCI_FEATURES. If the PSCI_FEATURES does not exist (PSCI 0.2 or
earlier) and the function return an error, then we considered SMCCC 1.0
is implemented.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

---
    Changes in v2:
        - Patch added
---
 xen/arch/arm/psci.c         | 34 +++++++++++++++++++++++++++++++++-
 xen/include/asm-arm/smccc.h |  5 ++++-
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/psci.c b/xen/arch/arm/psci.c
index 5dda35cd7c..bc7b2260e8 100644
--- a/xen/arch/arm/psci.c
+++ b/xen/arch/arm/psci.c
@@ -37,6 +37,7 @@
 #endif
 
 uint32_t psci_ver;
+uint32_t smccc_ver;
 
 static uint32_t psci_cpu_on_nr;
 
@@ -57,6 +58,14 @@ void call_psci_system_reset(void)
         call_smc(PSCI_0_2_FN32_SYSTEM_RESET, 0, 0, 0);
 }
 
+static int __init psci_features(uint32_t psci_func_id)
+{
+    if ( psci_ver < PSCI_VERSION(1, 0) )
+        return PSCI_NOT_SUPPORTED;
+
+    return call_smc(PSCI_1_0_FN32_PSCI_FEATURES, psci_func_id, 0, 0);
+}
+
 int __init psci_is_smc_method(const struct dt_device_node *psci)
 {
     int ret;
@@ -82,6 +91,24 @@ int __init psci_is_smc_method(const struct dt_device_node 
*psci)
     return 0;
 }
 
+static void __init psci_init_smccc(void)
+{
+    /* PSCI is using at least SMCC 1.0 calling convention. */
+    smccc_ver = ARM_SMCCC_VERSION_1_0;
+
+    if ( psci_features(ARM_SMCCC_VERSION_FID) != PSCI_NOT_SUPPORTED )
+    {
+        uint32_t ret;
+
+        ret = call_smc(ARM_SMCCC_VERSION_FID, 0, 0, 0);
+        if ( ret != ARM_SMCCC_NOT_SUPPORTED )
+            smccc_ver = ret;
+    }
+
+    printk(XENLOG_INFO "Using SMC Calling Convention v%u.%u\n",
+           SMCCC_VERSION_MAJOR(smccc_ver), SMCCC_VERSION_MINOR(smccc_ver));
+}
+
 int __init psci_init_0_1(void)
 {
     int ret;
@@ -173,7 +200,12 @@ int __init psci_init(void)
     if ( ret )
         ret = psci_init_0_1();
 
-    return ret;
+    if ( ret )
+        return ret;
+
+    psci_init_smccc();
+
+    return 0;
 }
 
 /*
diff --git a/xen/include/asm-arm/smccc.h b/xen/include/asm-arm/smccc.h
index caa2c9cc1b..bc067892c7 100644
--- a/xen/include/asm-arm/smccc.h
+++ b/xen/include/asm-arm/smccc.h
@@ -52,6 +52,8 @@
 
 #ifndef __ASSEMBLY__
 
+extern uint32_t smccc_ver;
+
 /* Check if this is fast call. */
 static inline bool smccc_is_fast_call(register_t funcid)
 {
@@ -137,8 +139,9 @@ static inline uint32_t smccc_get_owner(register_t funcid)
                       ARM_SMCCC_OWNER_ARCH,         \
                       0x8000)
 
-/* Only one error code defined in SMCCC */
+/* SMCCC error codes */
 #define ARM_SMCCC_ERR_UNKNOWN_FUNCTION  (-1)
+#define ARM_SMCCC_NOT_SUPPORTED         (-1)
 
 /* SMCCC function identifier range which is reserved for existing APIs */
 #define ARM_SMCCC_RESERVED_RANGE_START  0x0
-- 
2.11.0


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