[PATCH v2 08/16] xen/riscv: dt_processor_cpuid() implementation

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

Implements dt_processor_hartid() to get the hart ID of the given
device tree node and do some checks if CPU is available and given device
tree node has proper riscv,isa property.

As a helper function dt_get_cpuid() is introduced to deal specifically
with reg propery of a CPU device node.

Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in V2:
 - s/of_get_cpu_hwid()/dt_get_cpu_id().
 - Update prototype of dt_get_cpu_hwid(), use pointer-to-const for cpun arg.
 - Add empty line before last return in dt_get_cpu_hwid().
 - s/riscv_of_processor_hartid/dt_processor_cpuid().
 - Use pointer-to_const for node argument of dt_processor_cpuid().
 - Use for hart_id unsigned long type as according to the spec for RV128
   mhartid register will be 128 bit long.
 - Update commit message and subject.
 - use 'CPU' instead of 'HART'.
 - Drop thread argument of dt_get_cpu_id() (of_get_cpu_hwid) as it is
   expected to be always 0 according to RISC-V's DTS binding.
---
 xen/arch/riscv/include/asm/smp.h |  3 ++
 xen/arch/riscv/smpboot.c         | 66 ++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+)

diff --git a/xen/arch/riscv/include/asm/smp.h b/xen/arch/riscv/include/asm/smp.h
index 5e170b57b3..9d846a1338 100644
--- a/xen/arch/riscv/include/asm/smp.h
+++ b/xen/arch/riscv/include/asm/smp.h
@@ -26,6 +26,9 @@ static inline void set_cpuid_to_hartid(unsigned long cpuid,
 
 void setup_tp(unsigned int cpuid);
 
+struct dt_device_node;
+int dt_processor_cpuid(const struct dt_device_node *node, unsigned long 
*cpuid);
+
 #endif
 
 /*
diff --git a/xen/arch/riscv/smpboot.c b/xen/arch/riscv/smpboot.c
index 0371dfa53e..0b00dd0eb2 100644
--- a/xen/arch/riscv/smpboot.c
+++ b/xen/arch/riscv/smpboot.c
@@ -1,5 +1,8 @@
 #include <xen/cpumask.h>
+#include <xen/device_tree.h>
+#include <xen/errno.h>
 #include <xen/init.h>
+#include <xen/types.h>
 #include <xen/sections.h>
 
 cpumask_t __read_mostly cpu_online_map;
@@ -10,3 +13,66 @@ void __init smp_prepare_boot_cpu(void)
     cpumask_set_cpu(0, &cpu_possible_map);
     cpumask_set_cpu(0, &cpu_online_map);
 }
+
+/**
+ * dt_get_cpuid - Get the cpuid from a CPU device node
+ *
+ * @cpun: CPU number(logical index) for which device node is required
+ *
+ * Return: The cpuid for the CPU node or ~0ULL if not found.
+ */
+static unsigned long dt_get_cpuid(const struct dt_device_node *cpun)
+{
+    const __be32 *cell;
+    int ac;
+    uint32_t len;
+
+    ac = dt_n_addr_cells(cpun);
+    cell = dt_get_property(cpun, "reg", &len);
+    if ( !cell || !ac || ((sizeof(*cell) * ac) > len) )
+        return ~0ULL;
+
+    return dt_read_number(cell, ac);
+}
+
+/*
+ * Returns the cpuid of the given device tree node, or -ENODEV if the node
+ * isn't an enabled and valid RISC-V hart node.
+ */
+int dt_processor_cpuid(const struct dt_device_node *node, unsigned long *cpuid)
+{
+    const char *isa;
+
+    if ( !dt_device_is_compatible(node, "riscv") )
+    {
+        printk("Found incompatible CPU\n");
+        return -ENODEV;
+    }
+
+    *cpuid = dt_get_cpuid(node);
+    if ( *cpuid == ~0UL )
+    {
+        printk("Found CPU without CPU ID\n");
+        return -ENODEV;
+    }
+
+    if ( !dt_device_is_available(node))
+    {
+        printk("CPU with cpuid=%lu is not available\n", *cpuid);
+        return -ENODEV;
+    }
+
+    if ( dt_property_read_string(node, "riscv,isa", &isa) )
+    {
+        printk("CPU with cpuid=%lu has no \"riscv,isa\" property\n", *cpuid);
+        return -ENODEV;
+    }
+
+    if ( isa[0] != 'r' || isa[1] != 'v' )
+    {
+        printk("CPU with cpuid=%lu has an invalid ISA of \"%s\"\n", *cpuid, 
isa);
+        return -ENODEV;
+    }
+
+    return 0;
+}
-- 
2.49.0