errata: workaround for Cortex A78 errata 1821534

Cortex A78 erratum 1821534 is a Cat B erratum present in r0p0 and
r1p0 of the A78 processor core, it is fixed in r1p1.

SDEN can be found here:
https://documentation-service.arm.com/static/603e3733492bde1625aa8780

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I71057c4b9625cd9edc1a06946b453cf16ae5ea2c

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

@@ -275,6 +275,9 @@ For Cortex-A78, the following errata build flags are defined :
    CPU. This needs to be enabled for revisions r1p0 and r1p1, r0p0 has the same
    issue but there is no workaround for that revision.
 
+-  ``ERRATA_A78_1821534``: This applies errata 1821534 workaround to Cortex-A78
+   CPU. This needs to be enabled for revisions r0p0 and r1p0.
+
 For Neoverse N1, the following errata build flags are defined :
 
 -  ``ERRATA_N1_1073348``: This applies errata 1073348 workaround to Neoverse-N1

include/lib/cpus/aarch64/cortex_a78.h

@@ -30,6 +30,7 @@
 
 #define CORTEX_A78_ACTLR2_EL1				S3_0_C15_C1_1
 #define CORTEX_A78_ACTLR2_EL1_BIT_1			(ULL(1) << 1)
+#define CORTEX_A78_ACTLR2_EL1_BIT_2			(ULL(1) << 2)
 
 /*******************************************************************************
  * CPU Activity Monitor Unit register specific definitions.

lib/cpus/aarch64/cortex_a78.S

@@ -44,7 +44,7 @@ func check_errata_1688305
 	b	cpu_rev_var_ls
 endfunc check_errata_1688305
 
-	/* --------------------------------------------------
+/* --------------------------------------------------
  * Errata Workaround for Cortex A78 Errata #1941498.
  * This applies to revisions r0p0, r1p0, and r1p1.
  * x0: variant[4:7] and revision[0:3] of current cpu.
@@ -72,7 +72,7 @@ func check_errata_1941498
 	b	cpu_rev_var_ls
 endfunc check_errata_1941498
 
-	/* --------------------------------------------------
+/* --------------------------------------------------
  * Errata Workaround for A78 Erratum 1951500.
  * This applies to revisions r1p0 and r1p1 of A78.
  * The issue also exists in r0p0 but there is no fix
@@ -126,6 +126,34 @@ func check_errata_1951500
 	b	cpu_rev_var_range
 endfunc check_errata_1951500
 
+/* --------------------------------------------------
+ * Errata Workaround for Cortex A78 Errata #1821534.
+ * This applies to revisions r0p0 and r1p0.
+ * x0: variant[4:7] and revision[0:3] of current cpu.
+ * Shall clobber: x0-x17
+ * --------------------------------------------------
+ */
+func errata_a78_1821534_wa
+	/* Check revision. */
+	mov	x17, x30
+	bl	check_errata_1821534
+	cbz	x0, 1f
+
+	/* Set bit 2 in ACTLR2_EL1 */
+	mrs     x1, CORTEX_A78_ACTLR2_EL1
+	orr	x1, x1, #CORTEX_A78_ACTLR2_EL1_BIT_2
+	msr     CORTEX_A78_ACTLR2_EL1, x1
+	isb
+1:
+	ret	x17
+endfunc errata_a78_1821534_wa
+
+func check_errata_1821534
+	/* Applies to r0p0 and r1p0 */
+	mov	x1, #0x10
+	b	cpu_rev_var_ls
+endfunc check_errata_1821534
+
 	/* -------------------------------------------------
 	 * The CPU Ops reset function for Cortex-A78
 	 * -------------------------------------------------
@@ -150,6 +178,11 @@ func cortex_a78_reset_func
 	bl	errata_a78_1951500_wa
 #endif
 
+#if ERRATA_A78_1821534
+	mov	x0, x18
+	bl	errata_a78_1821534_wa
+#endif
+
 #if ENABLE_AMU
 	/* Make sure accesses from EL0/EL1 and EL2 are not trapped to EL3 */
 	mrs	x0, actlr_el3
@@ -207,6 +240,7 @@ func cortex_a78_errata_report
 	report_errata ERRATA_A78_1688305, cortex_a78, 1688305
 	report_errata ERRATA_A78_1941498, cortex_a78, 1941498
 	report_errata ERRATA_A78_1951500, cortex_a78, 1951500
+	report_errata ERRATA_A78_1821534, cortex_a78, 1821534
 
 	ldp	x8, x30, [sp], #16
 	ret

lib/cpus/cpu-ops.mk

@@ -307,6 +307,10 @@ ERRATA_A78_1941498	?=0
 # well but there is no workaround for that revision.
 ERRATA_A78_1951500	?=0
 
+# Flag to apply erratum 1821534 workaround during reset. This erratum applies
+# to revisions r0p0 and r1p0 of the A78 cpu.
+ERRATA_A78_1821534	?=0
+
 # Flag to apply T32 CLREX workaround during reset. This erratum applies
 # only to r0p0 and r1p0 of the Neoverse N1 cpu.
 ERRATA_N1_1043202	?=0
@@ -605,6 +609,10 @@ $(eval $(call add_define,ERRATA_A78_1941498))
 $(eval $(call assert_boolean,ERRATA_A78_1951500))
 $(eval $(call add_define,ERRATA_A78_1951500))
 
+# Process ERRATA_A78_1821534 flag
+$(eval $(call assert_boolean,ERRATA_A78_1821534))
+$(eval $(call add_define,ERRATA_A78_1821534))
+
 # Process ERRATA_N1_1043202 flag
 $(eval $(call assert_boolean,ERRATA_N1_1043202))
 $(eval $(call add_define,ERRATA_N1_1043202))