Hello Nathan,

On Fri, Feb 21, 2020 at 09:03:16AM -0600, Nathan Lynch wrote:

"Gautham R. Shenoy" [off-list ref] writes:

quoted

From: "Gautham R. Shenoy" <redacted>

Currently prior to entering an idle state on a Linux Guest, the
pseries cpuidle driver implement an idle_loop_prolog() and
idle_loop_epilog() functions which ensure that idle_purr is correctly
computed, and the hypervisor is informed that the CPU cycles have been
donated.

These prolog and epilog functions are also required in the default
idle call, i.e pseries_lpar_idle(). Hence move these accessor
functions to a common header file and call them from
pseries_lpar_idle(). Since the existing header files such as
asm/processor.h have enough clutter, create a new header file
asm/idle.h.

Signed-off-by: Gautham R. Shenoy <redacted>
---
 arch/powerpc/include/asm/idle.h        | 27 +++++++++++++++++++++++++++
 arch/powerpc/platforms/pseries/setup.c |  7 +++++--
 drivers/cpuidle/cpuidle-pseries.c      | 24 +-----------------------
 3 files changed, 33 insertions(+), 25 deletions(-)
 create mode 100644 arch/powerpc/include/asm/idle.h

diff --git a/arch/powerpc/include/asm/idle.h b/arch/powerpc/include/asm/idle.h
new file mode 100644
index 0000000..f32a7d8
--- /dev/null
+++ b/arch/powerpc/include/asm/idle.h

@@ -0,0 +1,27 @@
+#ifndef _ASM_POWERPC_IDLE_H
+#define _ASM_POWERPC_IDLE_H
+#include <asm/runlatch.h>
+
+static inline void idle_loop_prolog(unsigned long *in_purr)
+{
+	ppc64_runlatch_off();
+	*in_purr = mfspr(SPRN_PURR);
+	/*
+	 * Indicate to the HV that we are idle. Now would be
+	 * a good time to find other work to dispatch.
+	 */
+	get_lppaca()->idle = 1;
+}
+
+static inline void idle_loop_epilog(unsigned long in_purr)
+{
+	u64 wait_cycles;
+
+	wait_cycles = be64_to_cpu(get_lppaca()->wait_state_cycles);
+	wait_cycles += mfspr(SPRN_PURR) - in_purr;
+	get_lppaca()->wait_state_cycles = cpu_to_be64(wait_cycles);
+	get_lppaca()->idle = 0;
+
+	ppc64_runlatch_on();
+}
+#endif

Looks fine and correct as a cleanup, but asm/include/idle.h and
idle_loop_prolog, idle_loop_epilog, strike me as too generic for
pseries-specific code.

Should it be prefixed with pseries , i.e pseries_idle_prolog()
and pseries_idle_epilog() ?

Also, I am planning another round of cleanup to move all the
idle-related declaration from asm/include/processor.h to
asm/include/idle.h