[PATCH 7/7] xen/arm: get the number of cpus from device tree

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

The system might have fewer cpus than the GIC supports.

Changes in v2:
- return always at least 1 cpu;
- skip nodes with names that don't start with "cpu".

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
 xen/arch/arm/gic.c            |    4 +---
 xen/arch/arm/gic.h            |    2 +-
 xen/arch/arm/setup.c          |    3 ++-
 xen/common/device_tree.c      |   19 +++++++++++++++++++
 xen/include/xen/device_tree.h |    1 +
 5 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 5f06e08..0c6fab9 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -304,7 +304,7 @@ static void __cpuinit gic_hyp_disable(void)
 }
 
 /* Set up the GIC */
-int __init gic_init(void)
+void __init gic_init(void)
 {
     /* XXX FIXME get this from devicetree */
     gic.dbase = GIC_BASE_ADDRESS + GIC_DR_OFFSET;
@@ -328,8 +328,6 @@ int __init gic_init(void)
     gic.lr_mask = 0ULL;
 
     spin_unlock(&gic.lock);
-
-    return gic.cpus;
 }
 
 /* Set up the per-CPU parts of the GIC for a secondary CPU */
diff --git a/xen/arch/arm/gic.h b/xen/arch/arm/gic.h
index b2e1d7f..1bf1b02 100644
--- a/xen/arch/arm/gic.h
+++ b/xen/arch/arm/gic.h
@@ -147,7 +147,7 @@ extern int gic_route_irq_to_guest(struct domain *d, unsigned int irq,
 /* Accept an interrupt from the GIC and dispatch its handler */
 extern void gic_interrupt(struct cpu_user_regs *regs, int is_fiq);
 /* Bring up the interrupt controller, and report # cpus attached */
-extern int gic_init(void);
+extern void gic_init(void);
 /* Bring up a secondary CPU's per-CPU GIC interface */
 extern void gic_init_secondary_cpu(void);
 /* Take down a CPU's per-CPU GIC interface */
diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index a579a56..632e7e3 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -193,6 +193,7 @@ void __init start_xen(unsigned long boot_phys_offset,
         + (atag_paddr & ((1 << SECOND_SHIFT) - 1));
     fdt_size = device_tree_early_init(fdt);
 
+    cpus = device_tree_cpus(fdt);
     cmdline_parse(device_tree_bootargs(fdt));
 
     setup_pagetables(boot_phys_offset, get_xen_paddr());
@@ -203,7 +204,7 @@ void __init start_xen(unsigned long boot_phys_offset,
     console_init_preirq();
 #endif
 
-    cpus = gic_init();
+    gic_init();
     make_cpus_ready(cpus, boot_phys_offset);
 
     percpu_init_areas();
diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
index 3d1f0f4..5b6dab9 100644
--- a/xen/common/device_tree.c
+++ b/xen/common/device_tree.c
@@ -153,6 +153,25 @@ const char *device_tree_bootargs(const void *fdt)
     return prop->data;
 }
 
+int device_tree_cpus(const void *fdt)
+{
+    int node = 0, depth = 1;
+    int cpus = 0;
+
+    node = fdt_path_offset(fdt, "/cpus/cpu");
+    if ( node < 0 )
+        return 1; /* we have at least one cpu */
+
+    while ( node >= 0 && depth >= 0 ) {
+        if ( strncmp(fdt_get_name(fdt, node, NULL), "cpu", 3) )
+            continue;
+        node = fdt_next_node(fdt, node, &depth);
+        cpus++;
+    }
+
+    return cpus > 0 ? cpus : 1;
+}
+
 static int dump_node(const void *fdt, int node, const char *name, int depth,
                      u32 address_cells, u32 size_cells, void *data)
 {
diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
index 4d010c0..46bc0f8 100644
--- a/xen/include/xen/device_tree.h
+++ b/xen/include/xen/device_tree.h
@@ -49,6 +49,7 @@ bool_t device_tree_node_matches(const void *fdt, int node, const char *match);
 int device_tree_for_each_node(const void *fdt,
                               device_tree_node_func func, void *data);
 const char *device_tree_bootargs(const void *fdt);
+int device_tree_cpus(const void *fdt);
 void device_tree_dump(const void *fdt);
 
 #endif
-- 
1.7.2.5