Enable v8.6 WFE trap delays
This patch enables the v8.6 extension to add a delay before WFE traps
are taken. A weak hook plat_arm_set_twedel_scr_el3 has been added in
plat/common/aarch64/plat_common.c that disables this feature by default
but platform-specific code can override it when needed.
The only hook provided sets the TWED fields in SCR_EL3, there are similar
fields in HCR_EL2, SCTLR_EL2, and SCTLR_EL1 to control WFE trap delays in
lower ELs but these should be configured by code running at EL2 and/or EL1
depending on the platform configuration and is outside the scope of TF-A.
Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I0a9bb814205efeab693a3d0a0623e62144abba2d
diff --git a/plat/common/aarch64/plat_common.c b/plat/common/aarch64/plat_common.c
index 63871d9..b8a4d01 100644
--- a/plat/common/aarch64/plat_common.c
+++ b/plat/common/aarch64/plat_common.c
@@ -11,6 +11,7 @@
#if RAS_EXTENSION
#include <lib/extensions/ras.h>
#endif
+#include <lib/extensions/twed.h>
#include <lib/xlat_tables/xlat_mmu_helpers.h>
#include <plat/common/platform.h>
@@ -20,6 +21,7 @@
* platforms but may also be overridden by a platform if required.
*/
#pragma weak bl31_plat_runtime_setup
+#pragma weak plat_arm_set_twedel_scr_el3
#if SDEI_SUPPORT
#pragma weak plat_sdei_handle_masked_trigger
@@ -100,3 +102,16 @@
#endif
panic();
}
+
+/*******************************************************************************
+ * In v8.6+ platforms with delayed trapping of WFE this hook sets the delay. It
+ * is a weak function definition so can be overridden depending on the
+ * requirements of a platform. The only hook provided is for the TWED fields
+ * in SCR_EL3, the TWED fields in HCR_EL2, SCTLR_EL2, and SCTLR_EL1 should be
+ * configured as needed in lower exception levels.
+ ******************************************************************************/
+
+uint32_t plat_arm_set_twedel_scr_el3(void)
+{
+ return TWED_DISABLED;
+}