[PATCH v13 12/14] xen/arm: Implement PSCI SYSTEM_SUSPEND call (host interface)

[Mykola Kvach <mykola_kvach@xxxxxxxx>]

From: Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>

Invoke PSCI SYSTEM_SUSPEND to finalize Xen's suspend sequence on ARM64
platforms. Pass the Xen resume entry point (hyp_resume) to EL3 together
with a zero context ID, matching Linux.

This patch wires up only the host-side PSCI SYSTEM_SUSPEND invocation.
The resume trampoline and context restore are provided by earlier patches
in the series.

Only enable this path when CONFIG_SYSTEM_SUSPEND is set and PSCI
advertises SYSTEM_SUSPEND via PSCI_FEATURES.

Signed-off-by: Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>
Signed-off-by: Saeed Nowshadi <saeed.nowshadi@xxxxxxxxxx>
Signed-off-by: Mykyta Poturai <mykyta_poturai@xxxxxxxx>
Signed-off-by: Mykola Kvach <mykola_kvach@xxxxxxxx>
Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>
---
Changes in v13:
- Use the result returned by arm_smccc_smc() and drop the result pointer.

Changes in v9:
- cache SYSTEM_SUSPEND support using PSCI_FEATURES and gate the host call
  on the cached capability
- keep the cached SYSTEM_SUSPEND capability read-only after init
- log whether firmware reports SYSTEM_SUSPEND support
- pass an explicit zero context ID in the SYSTEM_SUSPEND call
- drop the stale note claiming hyp_resume is still a stub
---
 xen/arch/arm/include/asm/psci.h |  1 +
 xen/arch/arm/psci.c             | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/include/asm/psci.h b/xen/arch/arm/include/asm/psci.h
index 48a93e6b79..bb3c73496e 100644
--- a/xen/arch/arm/include/asm/psci.h
+++ b/xen/arch/arm/include/asm/psci.h
@@ -23,6 +23,7 @@ int call_psci_cpu_on(int cpu);
 void call_psci_cpu_off(void);
 void call_psci_system_off(void);
 void call_psci_system_reset(void);
+int call_psci_system_suspend(void);
 
 /* Range of allocated PSCI function numbers */
 #define        PSCI_FNUM_MIN_VALUE                 _AC(0,U)
diff --git a/xen/arch/arm/psci.c b/xen/arch/arm/psci.c
index 967cb4b77d..4d502216ce 100644
--- a/xen/arch/arm/psci.c
+++ b/xen/arch/arm/psci.c
@@ -17,23 +17,27 @@
 #include <asm/cpufeature.h>
 #include <asm/psci.h>
 #include <asm/acpi.h>
+#include <asm/suspend.h>
 
 /*
  * While a 64-bit OS can make calls with SMC32 calling conventions, for
  * some calls it is necessary to use SMC64 to pass or return 64-bit values.
- * For such calls PSCI_0_2_FN_NATIVE(x) will choose the appropriate
+ * For such calls PSCI_*_FN_NATIVE(x) will choose the appropriate
  * (native-width) function ID.
  */
 #ifdef CONFIG_ARM_64
 #define PSCI_0_2_FN_NATIVE(name)    PSCI_0_2_FN64_##name
+#define PSCI_1_0_FN_NATIVE(name)    PSCI_1_0_FN64_##name
 #else
 #define PSCI_0_2_FN_NATIVE(name)    PSCI_0_2_FN32_##name
+#define PSCI_1_0_FN_NATIVE(name)    PSCI_1_0_FN32_##name
 #endif
 
 uint32_t psci_ver;
 uint32_t smccc_ver;
 
 static uint32_t psci_cpu_on_nr;
+static bool __ro_after_init has_psci_system_suspend;
 
 #define PSCI_RET(res)   ((int32_t)(res).a0)
 
@@ -60,6 +64,26 @@ void call_psci_cpu_off(void)
     }
 }
 
+int call_psci_system_suspend(void)
+{
+#ifdef CONFIG_SYSTEM_SUSPEND
+    struct arm_smccc_res res;
+
+    if ( !has_psci_system_suspend )
+        return PSCI_NOT_SUPPORTED;
+
+    /* Context ID is unused for the Xen resume path. */
+    res = arm_smccc_smc(PSCI_1_0_FN_NATIVE(SYSTEM_SUSPEND),
+                        __pa(hyp_resume), 0);
+
+    return PSCI_RET(res);
+#else
+    dprintk(XENLOG_WARNING,
+            "SYSTEM_SUSPEND not supported (CONFIG_SYSTEM_SUSPEND disabled)\n");
+    return PSCI_NOT_SUPPORTED;
+#endif
+}
+
 void call_psci_system_off(void)
 {
     if ( psci_ver > PSCI_VERSION(0, 1) )
@@ -223,9 +247,15 @@ int __init psci_init(void)
 
     psci_init_smccc();
 
+    has_psci_system_suspend =
+        psci_features(PSCI_1_0_FN_NATIVE(SYSTEM_SUSPEND)) == 0;
+
     printk(XENLOG_INFO "Using PSCI v%u.%u\n",
            PSCI_VERSION_MAJOR(psci_ver), PSCI_VERSION_MINOR(psci_ver));
 
+    printk(XENLOG_DEBUG "PSCI SYSTEM_SUSPEND is %ssupported by firmware\n",
+           has_psci_system_suspend ? "" : "not ");
+
     return 0;
 }
 
-- 
2.53.0