partly reverts commit efb9ca08b5a2374b29938cdcab417ce4feb14b54. Selects
HAVE_GET_CYCLES_32 only on CPUs where it is safe to use it.
Currently consider the "_WORKAROUND" cases for 4000 and 4400 to be unsafe, but
should probably add other sub-architecture to the blacklist.
Do not define HAVE_GET_CYCLES because MIPS does not provide 64-bit tsc (only
32-bits).
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
CC: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
CC: David Miller <davem@xxxxxxxxxxxxx>
CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxxxxx>
CC: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
CC: linux-arch@xxxxxxxxxxxxxxx
---
arch/mips/Kconfig | 4 ++++
include/asm-mips/timex.h | 25 +++++++++++++++++++++++++
2 files changed, 29 insertions(+)
Index: linux-2.6-lttng/include/asm-mips/timex.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-mips/timex.h 2008-10-16 12:25:47.000000000 -0400
+++ linux-2.6-lttng/include/asm-mips/timex.h 2008-10-16 12:34:18.000000000 -0400
@@ -29,14 +29,39 @@
* which isn't an evil thing.
*
* We know that all SMP capable CPUs have cycle counters.
+ *
+ * Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
+ * HAVE_GET_CYCLES makes sure that this case is handled properly :
+ *
+ * Ralf Baechle <ralf@xxxxxxxxxxxxxx> :
+ * This avoids us executing an mfc0 c0_count instruction on processors which
+ * don't have but also on certain R4000 and R4400 versions where reading from
+ * the count register just in the very moment when its value equals c0_compare
+ * will result in the timer interrupt getting lost.
*/
typedef unsigned int cycles_t;
+#ifdef HAVE_GET_CYCLES_32
+static inline cycles_t get_cycles(void)
+{
+ return read_c0_count();
+}
+
+static inline void get_cycles_barrier(void)
+{
+}
+
+static inline cycles_t get_cycles_rate(void)
+{
+ return CLOCK_TICK_RATE;
+}
+#else
static inline cycles_t get_cycles(void)
{
return 0;
}
+#endif
#endif /* __KERNEL__ */
Index: linux-2.6-lttng/arch/mips/Kconfig
===================================================================
--- linux-2.6-lttng.orig/arch/mips/Kconfig 2008-10-16 12:25:47.000000000 -0400
+++ linux-2.6-lttng/arch/mips/Kconfig 2008-10-16 12:34:01.000000000 -0400
@@ -1581,6 +1581,10 @@ config CPU_R4000_WORKAROUNDS
config CPU_R4400_WORKAROUNDS
bool
+config HAVE_GET_CYCLES_32
+ def_bool y
+ depends on !CPU_R4400_WORKAROUNDS
+
#
# Use the generic interrupt handling code in kernel/irq/:
#
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
--
To unsubscribe from this list: send the line "unsubscribe linux-arch" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
