powerpc/pseries: Add extended_cede_processor() helper function.

This patch provides an extended_cede_processor() helper function
which takes the cede latency hint as an argument. This hint is to be passed
on to the hypervisor to cede to the corresponding state on platforms
which support it.

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 22 insertions, 0 deletions

diff --git a/arch/powerpc/platforms/pseries/plpar_wrappers.h b/arch/powerpc/platforms/pseries/plpar_wrappers.h
index a24a6b2333b2..0603c91538ae 100644
--- a/arch/powerpc/platforms/pseries/plpar_wrappers.h
+++ b/arch/powerpc/platforms/pseries/plpar_wrappers.h
@@ -9,11 +9,33 @@ static inline long poll_pending(void)
         return plpar_hcall_norets(H_POLL_PENDING);
 }
 
+static inline u8 get_cede_latency_hint(void)
+{
+        return get_lppaca()->gpr5_dword.fields.cede_latency_hint;
+}
+
+static inline void set_cede_latency_hint(u8 latency_hint)
+{
+        get_lppaca()->gpr5_dword.fields.cede_latency_hint = latency_hint;
+}
+
 static inline long cede_processor(void)
 {
         return plpar_hcall_norets(H_CEDE);
 }
 
+static inline long extended_cede_processor(unsigned long latency_hint)
+{
+        long rc;
+        u8 old_latency_hint = get_cede_latency_hint();
+
+        set_cede_latency_hint(latency_hint);
+        rc = cede_processor();
+        set_cede_latency_hint(old_latency_hint);
+
+        return rc;
+}
+
 static inline long vpa_call(unsigned long flags, unsigned long cpu,
                 unsigned long vpa)
 {