[Xen-devel] [PATCH 1/4] arm: parse PSCI node from the host device-tree

[Andre Przywara <andre.przywara@xxxxxxxxxx>]

The availability of a PSCI handler is advertised in the DTB.
Find and parse the node (described in the Linux device-tree binding)
and save the function number for bringing up a CPU for later usage.
We do some sanity checks, especially we deny using HVC as a callling
method, as it does not make much sense currently under Xen.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
---
 xen/arch/arm/smpboot.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
index 6c90fa6..97bd414 100644
--- a/xen/arch/arm/smpboot.c
+++ b/xen/arch/arm/smpboot.c
@@ -89,6 +89,44 @@ smp_clear_cpu_maps (void)
     cpu_logical_map(0) = READ_SYSREG(MPIDR_EL1) & MPIDR_HWID_MASK;
 }
 
+uint32_t psci_host_cpu_on_nr;
+
+static int __init psci_host_init(void)
+{
+    struct dt_device_node *psci;
+    int ret;
+    const char *prop_str;
+
+    psci = dt_find_compatible_node(NULL, NULL, "arm,psci");
+    if ( !psci )
+        return 1;
+
+    ret = dt_property_read_string(psci, "method", &prop_str);
+    if ( ret )
+    {
+        printk("/psci node does not provide a method (%d)\n", ret);
+        return 2;
+    }
+
+    /* Since Xen runs in HYP all of the time, it does not make sense to
+     * let it call into HYP for PSCI handling, since the handler won't
+     * just be there. So bail out with an error if "smc" is not used.
+     */
+    if ( strcmp(prop_str, "smc") )
+    {
+        printk("/psci method must be smc, but is: \"%s\"\n", prop_str);
+        return 3;
+    }
+
+    if ( !dt_property_read_u32(psci, "cpu_on", &psci_host_cpu_on_nr) )
+    {
+        printk("/psci node is missing the \"cpu_on\" property\n");
+        return 4;
+    }
+
+    return 0;
+}
+
 /* Parse the device tree and build the logical map array containing
  * MPIDR values related to logical cpus
  * Code base on Linux arch/arm/kernel/devtree.c
@@ -107,6 +145,11 @@ void __init smp_init_cpus(void)
     bool_t bootcpu_valid = 0;
     int rc;
 
+    if ( psci_host_init() == 0 )
+    {
+        printk(XENLOG_INFO "Using PSCI for SMP bringup\n");
+    }
+
     if ( (rc = arch_smp_init()) < 0 )
     {
         printk(XENLOG_WARNING "SMP init failed (%d)\n"
-- 
1.7.12.1


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