diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst
index 58b0572..fc853f3 100644
--- a/docs/design/cpu-specific-build-macros.rst
+++ b/docs/design/cpu-specific-build-macros.rst
@@ -275,6 +275,9 @@
    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
diff --git a/docs/license.rst b/docs/license.rst
index f0caa39..80f1118 100644
--- a/docs/license.rst
+++ b/docs/license.rst
@@ -81,6 +81,7 @@
    terms of the MIT license. These files are:
 
    -  ``include/dt-bindings/interrupt-controller/arm-gic.h``
+   -  ``include/dt-bindings/interrupt-controller/irq.h``
 
    See the original `Linux MIT license`_.
 
diff --git a/include/dt-bindings/interrupt-controller/arm-gic.h b/include/dt-bindings/interrupt-controller/arm-gic.h
index fbe07da..803cd9c 100644
--- a/include/dt-bindings/interrupt-controller/arm-gic.h
+++ b/include/dt-bindings/interrupt-controller/arm-gic.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2021, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2019-2021, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -9,21 +9,18 @@
 #ifndef _DT_BINDINGS_INTERRUPT_CONTROLLER_ARM_GIC_H
 #define _DT_BINDINGS_INTERRUPT_CONTROLLER_ARM_GIC_H
 
+#include <dt-bindings/interrupt-controller/irq.h>
+
 /* interrupt specifier cell 0 */
 
 #define GIC_SPI 0
 #define GIC_PPI 1
 
-#define IRQ_TYPE_NONE		0
-#define IRQ_TYPE_EDGE_RISING	1
-#define IRQ_TYPE_EDGE_FALLING	2
-#define IRQ_TYPE_EDGE_BOTH	(IRQ_TYPE_EDGE_FALLING | IRQ_TYPE_EDGE_RISING)
-#define IRQ_TYPE_LEVEL_HIGH	4
-#define IRQ_TYPE_LEVEL_LOW	8
-
 /*
  * Interrupt specifier cell 2.
+ * The flags in irq.h are valid, plus those below.
  */
 #define GIC_CPU_MASK_RAW(x) ((x) << 8)
+#define GIC_CPU_MASK_SIMPLE(num) GIC_CPU_MASK_RAW((1 << (num)) - 1)
 
 #endif
diff --git a/include/dt-bindings/interrupt-controller/irq.h b/include/dt-bindings/interrupt-controller/irq.h
new file mode 100644
index 0000000..94e7f95
--- /dev/null
+++ b/include/dt-bindings/interrupt-controller/irq.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2021, Arm Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * This header provides constants for most IRQ bindings.
+ *
+ * Most IRQ bindings include a flags cell as part of the IRQ specifier.
+ * In most cases, the format of the flags cell uses the standard values
+ * defined in this header.
+ */
+
+#ifndef _DT_BINDINGS_INTERRUPT_CONTROLLER_IRQ_H
+#define _DT_BINDINGS_INTERRUPT_CONTROLLER_IRQ_H
+
+#define IRQ_TYPE_NONE		0
+#define IRQ_TYPE_EDGE_RISING	1
+#define IRQ_TYPE_EDGE_FALLING	2
+#define IRQ_TYPE_EDGE_BOTH	(IRQ_TYPE_EDGE_FALLING | IRQ_TYPE_EDGE_RISING)
+#define IRQ_TYPE_LEVEL_HIGH	4
+#define IRQ_TYPE_LEVEL_LOW	8
+
+#endif
diff --git a/include/lib/cpus/aarch64/cortex_a78.h b/include/lib/cpus/aarch64/cortex_a78.h
index caa5120..4bc49f3 100644
--- a/include/lib/cpus/aarch64/cortex_a78.h
+++ b/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.
diff --git a/lib/cpus/aarch64/cortex_a78.S b/lib/cpus/aarch64/cortex_a78.S
index f61726b..8c5a45a 100644
--- a/lib/cpus/aarch64/cortex_a78.S
+++ b/lib/cpus/aarch64/cortex_a78.S
@@ -44,13 +44,13 @@
 	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.
-	 * Shall clobber: x0-x17
-	 * --------------------------------------------------
-	 */
+/* --------------------------------------------------
+ * 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.
+ * Shall clobber: x0-x17
+ * --------------------------------------------------
+ */
 func errata_a78_1941498_wa
 	/* Compare x0 against revision <= r1p1 */
 	mov	x17, x30
@@ -72,16 +72,16 @@
 	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
-	 * in that revision.
-	 * Inputs:
-	 * x0: variant[4:7] and revision[0:3] of current cpu.
-	 * Shall clobber: x0-x17
-	 * --------------------------------------------------
-	 */
+/* --------------------------------------------------
+ * 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
+ * in that revision.
+ * Inputs:
+ * x0: variant[4:7] and revision[0:3] of current cpu.
+ * Shall clobber: x0-x17
+ * --------------------------------------------------
+ */
 func errata_a78_1951500_wa
 	/* Compare x0 against revisions r1p0 - r1p1 */
 	mov	x17, x30
@@ -126,6 +126,34 @@
 	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 @@
 	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 @@
 	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
diff --git a/lib/cpus/cpu-ops.mk b/lib/cpus/cpu-ops.mk
index fb33346..541a2a2 100644
--- a/lib/cpus/cpu-ops.mk
+++ b/lib/cpus/cpu-ops.mk
@@ -307,6 +307,10 @@
 # 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 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))