Add support for Cortex-A57 erratum 826974 workaround

Change-Id: I45641551474f4c58c638aff8c42c0ab9a8ec78b4

docs/cpu-specific-build-macros.md

@@ -60,6 +60,9 @@ For Cortex-A57, following errata build flags are defined :
 *   `ERRATA_A57_813420`: This applies errata 813420 workaround to Cortex-A57
      CPU. This needs to be enabled only for revision r0p0 of the CPU.
 
+*   `ERRATA_A57_826974`: This applies errata 826974 workaround to Cortex-A57
+     CPU. This needs to be enabled only for revision <= r1p1 of the CPU.
+
 3.  CPU Specific optimizations
 ------------------------------
 

include/lib/cpus/aarch64/cortex_a57.h

@@ -61,6 +61,7 @@
  ******************************************************************************/
 #define CPUACTLR_EL1			S3_1_C15_C2_0	/* Instruction def. */
 
+#define CPUACTLR_DIS_LOAD_PASS_DMB	(1 << 59)
 #define CPUACTLR_DIS_OVERREAD		(1 << 52)
 #define CPUACTLR_NO_ALLOC_WBWA		(1 << 49)
 #define CPUACTLR_DCC_AS_DCCI		(1 << 44)

lib/cpus/aarch64/cortex_a57.S

@@ -167,6 +167,33 @@ disable_hint:
 	ret
 endfunc a57_disable_ldnp_overread
 
+	/* ---------------------------------------------------
+	 * Errata Workaround for Cortex A57 Errata #826974.
+	 * This applies only to revision <= r1p1 of Cortex A57.
+	 * Inputs:
+	 * x0: variant[4:7] and revision[0:3] of current cpu.
+	 * Clobbers : x0 - x5
+	 * ---------------------------------------------------
+	 */
+func errata_a57_826974_wa
+	/*
+	 * Compare x0 against revision r1p1
+	 */
+	cmp	x0, #0x11
+	b.ls	apply_826974
+#if LOG_LEVEL >= LOG_LEVEL_VERBOSE
+	b	print_revision_warning
+#else
+	ret
+#endif
+apply_826974:
+	mrs	x1, CPUACTLR_EL1
+	orr	x1, x1, #CPUACTLR_DIS_LOAD_PASS_DMB
+	msr	CPUACTLR_EL1, x1
+	ret
+endfunc errata_a57_826974_wa
+
+
 	/* -------------------------------------------------
 	 * The CPU Ops reset function for Cortex-A57.
 	 * Clobbers: x0-x5, x15, x19, x30
@@ -200,6 +227,11 @@ func cortex_a57_reset_func
 	bl	a57_disable_ldnp_overread
 #endif
 
+#if ERRATA_A57_826974
+	mov	x0, x15
+	bl	errata_a57_826974_wa
+#endif
+
 	/* ---------------------------------------------
 	 * Enable the SMP bit.
 	 * ---------------------------------------------

lib/cpus/cpu-ops.mk

@@ -74,6 +74,10 @@ ERRATA_A57_806969	?=0
 # only to revision r0p0 of the Cortex A57 cpu.
 ERRATA_A57_813420	?=0
 
+# Flag to apply erratum 826974 workaround during reset. This erratum applies
+# only to revision <= r1p1 of the Cortex A57 cpu.
+ERRATA_A57_826974	?=0
+
 # Process ERRATA_A53_826319 flag
 $(eval $(call assert_boolean,ERRATA_A53_826319))
 $(eval $(call add_define,ERRATA_A53_826319))
@@ -89,3 +93,7 @@ $(eval $(call add_define,ERRATA_A57_806969))
 # Process ERRATA_A57_813420 flag
 $(eval $(call assert_boolean,ERRATA_A57_813420))
 $(eval $(call add_define,ERRATA_A57_813420))
+
+# Process ERRATA_A57_826974 flag
+$(eval $(call assert_boolean,ERRATA_A57_826974))
+$(eval $(call add_define,ERRATA_A57_826974))