Cortex-A15: Implement workaround for errata 827671

This erratum can only be worked around on revisions >= r3p0 because the
register that needs to be accessed only exists in those revisions[1].

[1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0438g/CIHEAAAD.html

Change-Id: I5d773547d7a09b5bd01dabcd19ceeaf53c186faa
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>

docs/cpu-specific-build-macros.rst

@@ -76,6 +76,9 @@ For Cortex-A15, the following errata build flags are defined :
 -  ``ERRATA_A15_816470``: This applies errata 816470 workaround to Cortex-A15
    CPU. This needs to be enabled only for revision >= r3p0 of the CPU.
 
+-  ``ERRATA_A15_827671``: This applies errata 827671 workaround to Cortex-A15
+   CPU. This needs to be enabled only for revision >= r3p0 of the CPU.
+
 For Cortex-A53, the following errata build flags are defined :
 
 -  ``ERRATA_A53_819472``: This applies errata 819472 workaround to all

include/lib/cpus/aarch32/cortex_a15.h

@@ -9,6 +9,13 @@
 
 #include <lib/utils_def.h>
 
+/*******************************************************************************
+ * Auxiliary Control Register 2 specific definitions.
+ ******************************************************************************/
+#define CORTEX_A15_ACTLR2			p15, 1, c15, c0, 4
+
+#define CORTEX_A15_ACTLR2_INV_DCC_BIT		(U(1) << 0)
+
 /*******************************************************************************
  * Cortex-A15 midr with version/revision set to 0
  ******************************************************************************/

lib/cpus/aarch32/cortex_a15.S

@@ -62,6 +62,35 @@ func check_errata_816470
 	bx	lr
 endfunc check_errata_816470
 
+	/* ----------------------------------------------------
+	 * Errata Workaround for Cortex A15 Errata #827671.
+	 * This applies only to revision >= r3p0 of Cortex A15.
+	 * Inputs:
+	 * r0: variant[4:7] and revision[0:3] of current cpu.
+	 * Shall clobber: r0-r3
+	 * ----------------------------------------------------
+	 */
+func errata_a15_827671_wa
+	/*
+	 * Compare r0 against revision r3p0
+	 */
+	mov	r2, lr
+	bl	check_errata_827671
+	cmp	r0, #ERRATA_NOT_APPLIES
+	beq	1f
+	ldcopr	r0, CORTEX_A15_ACTLR2
+	orr	r0, #CORTEX_A15_ACTLR2_INV_DCC_BIT
+	stcopr	r0, CORTEX_A15_ACTLR2
+	isb
+1:
+	bx	r2
+endfunc errata_a15_827671_wa
+
+func check_errata_827671
+	mov	r1, #0x30
+	b	cpu_rev_var_hs
+endfunc check_errata_827671
+
 func check_errata_cve_2017_5715
 #if WORKAROUND_CVE_2017_5715
 	mov	r0, #ERRATA_APPLIES
@@ -86,6 +115,7 @@ func cortex_a15_errata_report
 	 * checking functions of each errata.
 	 */
 	report_errata ERRATA_A15_816470, cortex_a15, 816470
+	report_errata ERRATA_A15_827671, cortex_a15, 827671
 	report_errata WORKAROUND_CVE_2017_5715, cortex_a15, cve_2017_5715
 
 	pop	{r12, lr}
@@ -94,6 +124,13 @@ endfunc cortex_a15_errata_report
 #endif
 
 func cortex_a15_reset_func
+	mov	r5, lr
+	bl	cpu_get_rev_var
+
+#if ERRATA_A15_827671
+	bl	errata_a15_827671_wa
+#endif
+
 #if IMAGE_BL32 && WORKAROUND_CVE_2017_5715
 	ldcopr	r0, ACTLR
 	orr	r0, #CORTEX_A15_ACTLR_INV_BTB_BIT
@@ -103,6 +140,8 @@ func cortex_a15_reset_func
 	stcopr	r0, MVBAR
 	/* isb will be applied in the course of the reset func */
 #endif
+
+	mov	lr, r5
 	b	cortex_a15_enable_smp
 endfunc cortex_a15_reset_func
 

lib/cpus/cpu-ops.mk

@@ -57,6 +57,10 @@ endif
 # applies only to revision >= r3p0 of the Cortex A15 cpu.
 ERRATA_A15_816470	?=0
 
+# Flag to apply erratum 827671 workaround during reset. This erratum applies
+# only to revision >= r3p0 of the Cortex A15 cpu.
+ERRATA_A15_827671	?=0
+
 # Flag to apply erratum 819472 workaround during reset. This erratum applies
 # only to revision <= r0p1 of the Cortex A53 cpu.
 ERRATA_A53_819472	?=0
@@ -204,6 +208,10 @@ ERRATA_DSU_936184	?=0
 $(eval $(call assert_boolean,ERRATA_A15_816470))
 $(eval $(call add_define,ERRATA_A15_816470))
 
+# Process ERRATA_A15_827671 flag
+$(eval $(call assert_boolean,ERRATA_A15_827671))
+$(eval $(call add_define,ERRATA_A15_827671))
+
 # Process ERRATA_A53_819472 flag
 $(eval $(call assert_boolean,ERRATA_A53_819472))
 $(eval $(call add_define,ERRATA_A53_819472))