lib: el3_runtime: initialise actlr_el1 to hardware defaults

The context management library initialises the CPU context for the
secure/non-secure worlds to zero. This leads to zeros being stored
to the actual registers when we restore the CPU context, during a
world switch. Denver CPUs dont expect zero to be written to the
implementation defined, actlr_el1 register, at any point of time.
Writing a zero to some fields of this register, results in an
UNDEFINED exception.

This patch bases the context actlr_el1 value on the actual hardware
register, to maintain parity with the expected settings

Change-Id: I1c806d7ff12daa7fd1e5c72825494b81454948f2
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>

diff --git a/lib/el3_runtime/aarch64/context_mgmt.c b/lib/el3_runtime/aarch64/context_mgmt.c
index 2608d1fcc4fb9ea07865b771dfcfb94b31ab88fd..64340e667b7811f4fbf0cae00ed987e1b57e7d87 100644 (file)
--- a/lib/el3_runtime/aarch64/context_mgmt.c
+++ b/lib/el3_runtime/aarch64/context_mgmt.c
@@ -65,7 +65,7 @@ static void cm_init_context_common(cpu_context_t *ctx, const entry_point_info_t
        uint32_t scr_el3, pmcr_el0;
        el3_state_t *state;
        gp_regs_t *gp_regs;
-       unsigned long sctlr_elx;
+       unsigned long sctlr_elx, actlr_elx;
 
        assert(ctx);
 
@@ -173,6 +173,16 @@ static void cm_init_context_common(cpu_context_t *ctx, const entry_point_info_t
         */
        write_ctx_reg(get_sysregs_ctx(ctx), CTX_SCTLR_EL1, sctlr_elx);
 
+       /*
+        * Base the context ACTLR_EL1 on the current value, as it is
+        * implementation defined. The context restore process will write
+        * the value from the context to the actual register and can cause
+        * problems for processor cores that don't expect certain bits to
+        * be zero.
+        */
+       actlr_elx = read_actlr_el1();
+       write_ctx_reg((get_sysregs_ctx(ctx)), (CTX_ACTLR_EL1), (actlr_elx));
+
        if (security_state == SECURE) {
                /*
                 * Initialise PMCR_EL0 for secure context only, setting all