fix(cpus): workaround for Cortex-A78C erratum 1827440

Cortex-A78C erratum 1827440 is a Cat B erratum that applies to
revision r0p0 and is fixed in r0p1.

The workaround is to set CPUACTLR2_EL1[2], which forces atomic store
operations to write-back memory to be performed in the L1 data cache.

SDEN documentation:
https://developer.arm.com/documentation/SDEN1707916/latest

Signed-off-by: Bipin Ravi <bipin.ravi@arm.com>
Change-Id: I41d8ef48f70216ec66bf2b0f4f03ea8d8c261ee7

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

@@ -353,6 +353,10 @@ For Cortex-A78C, the following errata build flags are defined :
   Cortex-A78C CPU. This needs to be enabled for revision r0p0. The erratum is
   fixed in r0p1.
 
+- ``ERRATA_A78C_1827440`` : This applies errata 1827440 workaround to
+  Cortex-A78C CPU. This needs to be enabled for revision r0p0. The erratum is
+  fixed in r0p1.
+
 - ``ERRATA_A78C_2132064`` : This applies errata 2132064 workaround to
   Cortex-A78C CPU. This needs to be enabled for revisions r0p1, r0p2 and
   it is still open.

lib/cpus/aarch64/cortex_a78c.S

@@ -44,6 +44,33 @@ func check_errata_1827430
 	b	cpu_rev_var_ls
 endfunc check_errata_1827430
 
+/* --------------------------------------------------
+ * Errata Workaround for A78C Erratum 1827440.
+ * This applies to revision r0p0 of the Cortex A78C
+ * processor and is fixed in r0p1.
+ * x0: variant[4:7] and revision[0:3] of current cpu.
+ * Shall clobber: x0-x17
+ * --------------------------------------------------
+ */
+func errata_a78c_1827440_wa
+	mov	x17, x30
+	bl	check_errata_1827440
+	cbz	x0, 1f
+
+	/* Force Atomic Store to WB memory be done in L1 data cache */
+	mrs	x1, CORTEX_A78C_CPUACTLR2_EL1
+	orr	x1, x1, #BIT(2)
+	msr	CORTEX_A78C_CPUACTLR2_EL1, x1
+1:
+	ret	x17
+endfunc errata_a78c_1827440_wa
+
+func check_errata_1827440
+	/* Applies to revision r0p0 only */
+	mov	x1, #0x00
+	b	cpu_rev_var_ls
+endfunc check_errata_1827440
+
 /* --------------------------------------------------
  * Errata Workaround for Cortex A78C Erratum 2376749.
  * This applies to revision r0p1 and r0p2 of the A78C
@@ -257,6 +284,11 @@ func cortex_a78c_reset_func
 	bl	errata_a78c_1827430_wa
 #endif
 
+#if ERRATA_A78C_1827440
+	mov	x0, x18
+	bl	errata_a78c_1827440_wa
+#endif
+
 #if ERRATA_A78C_2132064
 	mov	x0, x18
 	bl	errata_a78c_2132064_wa
@@ -332,6 +364,7 @@ func cortex_a78c_errata_report
 	 * checking functions of each errata.
 	 */
 	report_errata ERRATA_A78C_1827430, cortex_a78c, 1827430
+	report_errata ERRATA_A78C_1827440, cortex_a78c, 1827440
 	report_errata ERRATA_A78C_2132064, cortex_a78c, 2132064
 	report_errata ERRATA_A78C_2242638, cortex_a78c, 2242638
 	report_errata ERRATA_A78C_2376749, cortex_a78c, 2376749

lib/cpus/cpu-ops.mk

@@ -358,6 +358,10 @@ CPU_FLAG_LIST += ERRATA_A78_AE_2395408
 # to revision r0p0 of the A78C cpu. It is fixed in r0p1.
 CPU_FLAG_LIST += ERRATA_A78C_1827430
 
+# Flag to apply erratum 1827440 workaround during reset. This erratum applies
+# to revision r0p0 of the A78C cpu. It is fixed in r0p1.
+CPU_FLAG_LIST += ERRATA_A78C_1827440
+
 # Flag to apply erratum 2132064 workaround during reset. This erratum applies
 # to revisions r0p1 and r0p2 of the A78C cpu. It is still open.
 CPU_FLAG_LIST += ERRATA_A78C_2132064