[kvm-unit-tests PATCH V5 4/5] lib/powerpc: Implement generic delay function for use in unit tests

[Suraj Jitindar Singh <sjitindarsingh@gmail.com>]

It would be nice if we had a generic delay function which could be used
in unit tests, add one.

Add the variable tb_hz used to store the time base frequency which is read
from the device tree on setup.

Add functions mdelay, udelay and delay in processor.c to delay for a given
number of milliseconds, microseconds and time base ticks respectively.

Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>

---

Change Log:

V2 -> V3:
	- Add patch to series
V3 -> V4:
	- Reword sleep->delay
	- Move cpu_relax to asm-generic/barrier.h
	- Add assert to catch when delay fns called with too large values
V4 -> V5:
	- Remove unnecessary assert statements
---
 lib/asm-generic/barrier.h   |  4 ++++
 lib/powerpc/asm/processor.h | 19 +++++++++++++++++++
 lib/powerpc/asm/setup.h     |  2 ++
 lib/powerpc/processor.c     | 15 +++++++++++++++
 lib/powerpc/setup.c         |  9 +++++++++
 5 files changed, 49 insertions(+)

diff --git a/lib/asm-generic/barrier.h b/lib/asm-generic/barrier.h
index 12ae782..6a990ff 100644
--- a/lib/asm-generic/barrier.h
+++ b/lib/asm-generic/barrier.h
@@ -28,4 +28,8 @@
 #define smp_wmb()	wmb()
 #endif
 
+#ifndef cpu_relax
+#define cpu_relax()	asm volatile ("":::"memory")
+#endif
+
 #endif /* _ASM_BARRIER_H_ */
diff --git a/lib/powerpc/asm/processor.h b/lib/powerpc/asm/processor.h
index 09692bd..ac001e1 100644
--- a/lib/powerpc/asm/processor.h
+++ b/lib/powerpc/asm/processor.h
@@ -1,6 +1,7 @@
 #ifndef _ASMPOWERPC_PROCESSOR_H_
 #define _ASMPOWERPC_PROCESSOR_H_
 
+#include <libcflat.h>
 #include <asm/ptrace.h>
 
 #ifndef __ASSEMBLY__
@@ -8,4 +9,22 @@ void handle_exception(int trap, void (*func)(struct pt_regs *, void *), void *);
 void do_handle_exception(struct pt_regs *regs);
 #endif /* __ASSEMBLY__ */
 
+static inline uint64_t get_tb(void)
+{
+	uint64_t tb;
+
+	asm volatile ("mfspr %[tb],268" : [tb] "=r" (tb));
+
+	return tb;
+}
+
+extern void delay(uint64_t cycles);
+extern void udelay(uint64_t us);
+
+static inline void mdelay(uint64_t ms)
+{
+	while (ms--)
+		udelay(1000);
+}
+
 #endif /* _ASMPOWERPC_PROCESSOR_H_ */
diff --git a/lib/powerpc/asm/setup.h b/lib/powerpc/asm/setup.h
index b1e1e5a..23b4156 100644
--- a/lib/powerpc/asm/setup.h
+++ b/lib/powerpc/asm/setup.h
@@ -11,6 +11,8 @@
 extern u32 cpus[NR_CPUS];
 extern int nr_cpus;
 
+extern uint64_t tb_hz;
+
 #define NR_MEM_REGIONS		8
 #define MR_F_PRIMARY		(1U << 0)
 struct mem_region {
diff --git a/lib/powerpc/processor.c b/lib/powerpc/processor.c
index a78bc3c..056a61f 100644
--- a/lib/powerpc/processor.c
+++ b/lib/powerpc/processor.c
@@ -5,6 +5,8 @@
 #include <libcflat.h>
 #include <asm/processor.h>
 #include <asm/ptrace.h>
+#include <asm/setup.h>
+#include <asm/barrier.h>
 
 static struct {
 	void (*func)(struct pt_regs *, void *data);
@@ -36,3 +38,16 @@ void do_handle_exception(struct pt_regs *regs)
 	printf("unhandled cpu exception 0x%lx\n", regs->trap);
 	abort();
 }
+
+void delay(uint64_t cycles)
+{
+	uint64_t start = get_tb();
+
+	while ((get_tb() - start) < cycles)
+		cpu_relax();
+}
+
+void udelay(uint64_t us)
+{
+	delay((us * tb_hz) / 1000000);
+}
diff --git a/lib/powerpc/setup.c b/lib/powerpc/setup.c
index e3d2afa..9153f7b 100644
--- a/lib/powerpc/setup.c
+++ b/lib/powerpc/setup.c
@@ -24,6 +24,7 @@ extern void setup_args_progname(const char *args);
 
 u32 cpus[NR_CPUS] = { [0 ... NR_CPUS-1] = (~0U) };
 int nr_cpus;
+uint64_t tb_hz;
 
 struct mem_region mem_regions[NR_MEM_REGIONS];
 phys_addr_t __physical_start, __physical_end;
@@ -32,6 +33,7 @@ unsigned __icache_bytes, __dcache_bytes;
 struct cpu_set_params {
 	unsigned icache_bytes;
 	unsigned dcache_bytes;
+	uint64_t tb_hz;
 };
 
 #define EXCEPTION_STACK_SIZE	(32*1024) /* 32kB */
@@ -72,6 +74,12 @@ static void cpu_set(int fdtnode, u32 regval, void *info)
 		data = (u32 *)prop->data;
 		params->dcache_bytes = fdt32_to_cpu(*data);
 
+		prop = fdt_get_property(dt_fdt(), fdtnode,
+					"timebase-frequency", NULL);
+		assert(prop != NULL);
+		data = (u32 *)prop->data;
+		params->tb_hz = fdt32_to_cpu(*data);
+
 		read_common_info = true;
 	}
 }
@@ -86,6 +94,7 @@ static void cpu_init(void)
 	assert(ret == 0);
 	__icache_bytes = params.icache_bytes;
 	__dcache_bytes = params.dcache_bytes;
+	tb_hz = params.tb_hz;
 
 	/* Interrupt Endianness */
 
-- 
2.5.5