Workaround for Neoverse N1 erratum 1207823

Neoverse N1 erratum 1207823 is a Cat B erratum [1],
present in older revisions of the Neoverse N1 processor core.
The workaround is to set a bit in the implementation defined
CPUACTLR2_EL1 system register.

[1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.pjdoc-466751330-10325/index.html

Change-Id: Ia932337821f1ef0d644db3612480462a8d924d21
Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>

docs/design/cpu-specific-build-macros.rst

@@ -237,6 +237,9 @@ For Neoverse N1, the following errata build flags are defined :
 -  ``ERRATA_N1_1165347``: This applies errata 1165347 workaround to Neoverse-N1
    CPU. This needs to be enabled only for revision <= r2p0 of the CPU.
 
+-  ``ERRATA_N1_1207823``: This applies errata 1207823 workaround to Neoverse-N1
+   CPU. This needs to be enabled only for revision <= r2p0 of the CPU.
+
 -  ``ERRATA_N1_1315703``: This applies errata 1315703 workaround to Neoverse-N1
    CPU. This needs to be enabled only for revision <= r3p0 of the CPU.
 

include/lib/cpus/aarch64/neoverse_n1.h

@@ -41,6 +41,7 @@
 
 #define NEOVERSE_N1_CPUACTLR2_EL1_BIT_0		(ULL(1) << 0)
 #define NEOVERSE_N1_CPUACTLR2_EL1_BIT_2		(ULL(1) << 2)
+#define NEOVERSE_N1_CPUACTLR2_EL1_BIT_11	(ULL(1) << 11)
 #define NEOVERSE_N1_CPUACTLR2_EL1_BIT_15	(ULL(1) << 15)
 #define NEOVERSE_N1_CPUACTLR2_EL1_BIT_16	(ULL(1) << 16)
 #define NEOVERSE_N1_CPUACTLR2_EL1_BIT_59	(ULL(1) << 59)

lib/cpus/aarch64/neoverse_n1.S

@@ -157,6 +157,33 @@ func check_errata_1165347
 	b	cpu_rev_var_ls
 endfunc check_errata_1165347
 
+/* --------------------------------------------------
+ * Errata Workaround for Neoverse N1 Errata #1207823
+ * This applies to revision <=r2p0 of Neoverse N1.
+ * Inputs:
+ * x0: variant[4:7] and revision[0:3] of current cpu.
+ * Shall clobber: x0-x17
+ * --------------------------------------------------
+ */
+func errata_n1_1207823_wa
+	/* Compare x0 against revision r2p0 */
+	mov	x17, x30
+	bl	check_errata_1207823
+	cbz	x0, 1f
+	mrs	x1, NEOVERSE_N1_CPUACTLR2_EL1
+	orr	x1, x1, NEOVERSE_N1_CPUACTLR2_EL1_BIT_11
+	msr	NEOVERSE_N1_CPUACTLR2_EL1, x1
+	isb
+1:
+	ret	x17
+endfunc errata_n1_1207823_wa
+
+func check_errata_1207823
+	/* Applies to <=r2p0 */
+	mov	x1, #0x20
+	b	cpu_rev_var_ls
+endfunc check_errata_1207823
+
 /* --------------------------------------------------
  * Errata Workaround for Neoverse N1 Erratum 1315703.
  * This applies to revision <= r3p0 of Neoverse N1.
@@ -220,6 +247,11 @@ func neoverse_n1_reset_func
 	bl	errata_n1_1165347_wa
 #endif
 
+#if ERRATA_N1_1207823
+	mov	x0, x18
+	bl	errata_n1_1207823_wa
+#endif
+
 #if ERRATA_N1_1315703
 	mov	x0, x18
 	bl	errata_n1_1315703_wa
@@ -285,6 +317,7 @@ func neoverse_n1_errata_report
 	report_errata ERRATA_N1_1073348, neoverse_n1, 1073348
 	report_errata ERRATA_N1_1130799, neoverse_n1, 1130799
 	report_errata ERRATA_N1_1165347, neoverse_n1, 1165347
+	report_errata ERRATA_N1_1207823, neoverse_n1, 1207823
 	report_errata ERRATA_N1_1315703, neoverse_n1, 1315703
 	report_errata ERRATA_DSU_936184, neoverse_n1, dsu_936184
 

lib/cpus/cpu-ops.mk

@@ -250,6 +250,10 @@ ERRATA_N1_1130799	?=0
 # only to revision <= r2p0 of the Neoverse N1 cpu.
 ERRATA_N1_1165347	?=0
 
+# Flag to apply erratum 1207823 workaround during reset. This erratum applies
+# only to revision <= r2p0 of the Neoverse N1 cpu.
+ERRATA_N1_1207823	?=0
+
 # Flag to apply erratum 1315703 workaround during reset. This erratum applies
 # to revisions before r3p1 of the Neoverse N1 cpu.
 ERRATA_N1_1315703	?=1
@@ -455,6 +459,10 @@ $(eval $(call add_define,ERRATA_N1_1130799))
 $(eval $(call assert_boolean,ERRATA_N1_1165347))
 $(eval $(call add_define,ERRATA_N1_1165347))
 
+# Process ERRATA_N1_1207823 flag
+$(eval $(call assert_boolean,ERRATA_N1_1207823))
+$(eval $(call add_define,ERRATA_N1_1207823))
+
 # Process ERRATA_N1_1315703 flag
 $(eval $(call assert_boolean,ERRATA_N1_1315703))
 $(eval $(call add_define,ERRATA_N1_1315703))