Correct usage of data and instruction barriers
The current code does not always use data and instruction
barriers as required by the architecture and frequently uses
barriers excessively due to their inclusion in all of the
write_*() helper functions.
Barriers should be used explicitly in assembler or C code
when modifying processor state that requires the barriers in
order to enable review of correctness of the code.
This patch removes the barriers from the helper functions and
introduces them as necessary elsewhere in the code.
PORTING NOTE: check any port of Trusted Firmware for use of
system register helper functions for reliance on the previous
barrier behaviour and add explicit barriers as necessary.
Fixes ARM-software/tf-issues#92
Change-Id: Ie63e187404ff10e0bdcb39292dd9066cb84c53bf
diff --git a/plat/fvp/plat_pm.c b/plat/fvp/plat_pm.c
index 5430fff..f80e2d7 100644
--- a/plat/fvp/plat_pm.c
+++ b/plat/fvp/plat_pm.c
@@ -54,7 +54,11 @@
if (target_afflvl != MPIDR_AFFLVL0)
return PSCI_E_INVALID_PARAMS;
- /* Enter standby state */
+ /*
+ * Enter standby state
+ * dsb is good practice before using wfi to enter low power states
+ */
+ dsb();
wfi();
return PSCI_E_SUCCESS;