Merge pull request #857 from Andre-ARM/a53-855873

ARM Cortex-A53 erratum 855873 workaround

3 files changed, 66 insertions, 1 deletions

diff --git a/lib/cpus/aarch64/cortex_a53.S b/lib/cpus/aarch64/cortex_a53.S
index 1dd8a865..a36666bc 100644
--- a/lib/cpus/aarch64/cortex_a53.S
+++ b/lib/cpus/aarch64/cortex_a53.S
@@ -129,6 +129,39 @@ func check_errata_disable_non_temporal_hint
 	b	cpu_rev_var_ls
 endfunc check_errata_disable_non_temporal_hint
 
+	/* --------------------------------------------------
+	 * Errata Workaround for Cortex A53 Errata #855873.
+	 *
+	 * This applies only to revisions >= r0p3 of Cortex A53.
+	 * Earlier revisions of the core are affected as well, but don't
+	 * have the chicken bit in the CPUACTLR register. It is expected that
+	 * the rich OS takes care of that, especially as the workaround is
+	 * shared with other erratas in those revisions of the CPU.
+	 * Inputs:
+	 * x0: variant[4:7] and revision[0:3] of current cpu.
+	 * Shall clobber: x0-x17
+	 * --------------------------------------------------
+	 */
+func errata_a53_855873_wa
+	/*
+	 * Compare x0 against revision r0p3 and higher
+	 */
+        mov     x17, x30
+        bl      check_errata_855873
+        cbz     x0, 1f
+
+	mrs	x1, CPUACTLR_EL1
+	orr	x1, x1, #CPUACTLR_ENDCCASCI
+	msr	CPUACTLR_EL1, x1
+1:
+	ret	x17
+endfunc errata_a53_855873_wa
+
+func check_errata_855873
+	mov	x1, #0x03
+	b	cpu_rev_var_hs
+endfunc check_errata_855873
+
 	/* -------------------------------------------------
 	 * The CPU Ops reset function for Cortex-A53.
 	 * Shall clobber: x0-x19
@@ -150,6 +183,11 @@ func cortex_a53_reset_func
 	bl	a53_disable_non_temporal_hint
 #endif
 
+#if ERRATA_A53_855873
+	mov	x0, x18
+	bl	errata_a53_855873_wa
+#endif
+
 	/* ---------------------------------------------
 	 * Enable the SMP bit.
 	 * ---------------------------------------------
@@ -238,6 +276,7 @@ func cortex_a53_errata_report
 	 */
 	report_errata ERRATA_A53_826319, cortex_a53, 826319
 	report_errata ERRATA_A53_836870, cortex_a53, disable_non_temporal_hint
+	report_errata ERRATA_A53_855873, cortex_a53, 855873
 
 	ldp	x8, x30, [sp], #16
 	ret
@@ -255,13 +294,15 @@ endfunc cortex_a53_errata_report
 	 */
 .section .rodata.cortex_a53_regs, "aS"
 cortex_a53_regs:  /* The ascii list of register names to be reported */
-	.asciz	"cpuectlr_el1", "cpumerrsr_el1", "l2merrsr_el1", ""
+	.asciz	"cpuectlr_el1", "cpumerrsr_el1", "l2merrsr_el1", \
+		"cpuactlr_el1", ""
 
 func cortex_a53_cpu_reg_dump
 	adr	x6, cortex_a53_regs
 	mrs	x8, CPUECTLR_EL1
 	mrs	x9, CPUMERRSR_EL1
 	mrs	x10, L2MERRSR_EL1
+	mrs	x11, CPUACTLR_EL1
 	ret
 endfunc cortex_a53_cpu_reg_dump
 
diff --git a/lib/cpus/aarch64/cpu_helpers.S b/lib/cpus/aarch64/cpu_helpers.S
index 6a3669de..47cb6a2d 100644
--- a/lib/cpus/aarch64/cpu_helpers.S
+++ b/lib/cpus/aarch64/cpu_helpers.S
@@ -234,6 +234,20 @@ func cpu_rev_var_ls
 	ret
 endfunc cpu_rev_var_ls
 
+/*
+ * Compare the CPU's revision-variant (x0) with a given value (x1), for errata
+ * application purposes. If the revision-variant is higher than or same as a
+ * given value, indicates that errata applies; otherwise not.
+ */
+	.globl	cpu_rev_var_hs
+func cpu_rev_var_hs
+	mov	x2, #ERRATA_APPLIES
+	mov	x3, #ERRATA_NOT_APPLIES
+	cmp	x0, x1
+	csel	x0, x2, x3, hs
+	ret
+endfunc cpu_rev_var_hs
+
 #if REPORT_ERRATA
 /*
  * void print_errata_status(void);
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index 7d7db203..132ab6f7 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -66,6 +66,12 @@ ERRATA_A53_826319	?=0
 # erratum workaround is enabled by default in hardware.
 ERRATA_A53_836870	?=0
 
+# Flag to apply errata 855873 during reset. This errata applies to all
+# revisions of the Cortex A53 CPU, but this firmware workaround only works
+# for revisions r0p3 and higher. Earlier revisions are taken care
+# of by the rich OS.
+ERRATA_A53_855873	?=0
+
 # Flag to apply erratum 806969 workaround during reset. This erratum applies
 # only to revision r0p0 of the Cortex A57 cpu.
 ERRATA_A57_806969	?=0
@@ -106,6 +112,10 @@ $(eval $(call add_define,ERRATA_A53_826319))
 $(eval $(call assert_boolean,ERRATA_A53_836870))
 $(eval $(call add_define,ERRATA_A53_836870))
 
+# Process ERRATA_A53_855873 flag
+$(eval $(call assert_boolean,ERRATA_A53_855873))
+$(eval $(call add_define,ERRATA_A53_855873))
+
 # Process ERRATA_A57_806969 flag
 $(eval $(call assert_boolean,ERRATA_A57_806969))
 $(eval $(call add_define,ERRATA_A57_806969))