fix(errata): workaround for Cortex-A78 erratum 2395406

Cortex-A78 erratum 2395406 is a cat B erratum that applies to revisions
r0p0 - r1p2 and is still open. The workaround is to set bit[40] of
CPUACTLR2 which will disable folding of demand requests into older
prefetches with L2 miss requests outstanding.

SDEN can be found here:
https://developer.arm.com/documentation/SDEN1401784

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: If06f988f05f925c2a4bed3e6a9414b6acdfec894

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

@@ -300,6 +300,10 @@ For Cortex-A78, the following errata build flags are defined :
    CPU. This needs to be enabled for revisions r0p0, r1p0, r1p1, and r1p2, and
    it is still open.
 
+-  ``ERRATA_A78_2395406``: This applies errata 2395406 workaround to Cortex-A78
+   CPU. This needs to be enabled for revisions r0p0, r1p0, r1p1, and r1p2, and
+   it is still open.
+
 For Cortex-A78 AE, the following errata build flags are defined :
 
 - ``ERRATA_A78_AE_1941500`` : This applies errata 1941500 workaround to

lib/cpus/aarch64/cortex_a78.S

@@ -295,6 +295,34 @@ func check_errata_2376745
 	b	cpu_rev_var_ls
 endfunc check_errata_2376745
 
+/* --------------------------------------------------
+ * Errata Workaround for Cortex A78 Errata 2395406.
+ * This applies to revisions r0p0, r1p0, r1p1, and r1p2.
+ * It is still open.
+ * x0: variant[4:7] and revision[0:3] of current cpu.
+ * Shall clobber: x0-x1, x17
+ * --------------------------------------------------
+ */
+func errata_a78_2395406_wa
+	/* Check revision. */
+	mov	x17, x30
+	bl	check_errata_2395406
+	cbz	x0, 1f
+
+	/* Apply the workaround. */
+	mrs	x1, CORTEX_A78_ACTLR2_EL1
+	orr	x1, x1, #BIT(40)
+	msr	CORTEX_A78_ACTLR2_EL1, x1
+1:
+	ret	x17
+endfunc errata_a78_2395406_wa
+
+func check_errata_2395406
+	/* Applies to r0p0, r0p1, r1p1, and r1p2 */
+	mov	x1, #CPU_REV(1, 2)
+	b	cpu_rev_var_ls
+endfunc check_errata_2395406
+
 func check_errata_cve_2022_23960
 #if WORKAROUND_CVE_2022_23960
 	mov	x0, #ERRATA_APPLIES
@@ -353,6 +381,11 @@ func cortex_a78_reset_func
 	bl	errata_a78_2376745_wa
 #endif
 
+#if ERRATA_A78_2395406
+	mov	x0, x18
+	bl	errata_a78_2395406_wa
+#endif
+
 #if ENABLE_AMU
 	/* Make sure accesses from EL0/EL1 and EL2 are not trapped to EL3 */
 	mrs	x0, actlr_el3
@@ -424,6 +457,7 @@ func cortex_a78_errata_report
 	report_errata ERRATA_A78_2132060, cortex_a78, 2132060
 	report_errata ERRATA_A78_2242635, cortex_a78, 2242635
 	report_errata ERRATA_A78_2376745, cortex_a78, 2376745
+	report_errata ERRATA_A78_2395406, cortex_a78, 2395406
 	report_errata WORKAROUND_CVE_2022_23960, cortex_a78, cve_2022_23960
 
 	ldp	x8, x30, [sp], #16

lib/cpus/cpu-ops.mk

@@ -337,6 +337,10 @@ ERRATA_A78_2242635	?=0
 # to revisions r0p0, r1p0, r1p1, and r1p2 of the A78 cpu. It is still open.
 ERRATA_A78_2376745	?=0
 
+# Flag to apply erratum 2395406 workaround during reset. This erratum applies
+# to revisions r0p0, r1p0, r1p1, and r1p2 of the A78 cpu. It is still open.
+ERRATA_A78_2395406	?=0
+
 # Flag to apply erratum 1941500 workaround during reset. This erratum applies
 # to revisions r0p0 and r0p1 of the A78 AE cpu. It is still open.
 ERRATA_A78_AE_1941500	?=0
@@ -850,6 +854,10 @@ $(eval $(call add_define,ERRATA_A78_2242635))
 $(eval $(call assert_boolean,ERRATA_A78_2376745))
 $(eval $(call add_define,ERRATA_A78_2376745))
 
+# Process ERRATA_A78_2395406 flag
+$(eval $(call assert_boolean,ERRATA_A78_2395406))
+$(eval $(call add_define,ERRATA_A78_2395406))
+
 # Process ERRATA_A78_AE_1941500 flag
 $(eval $(call assert_boolean,ERRATA_A78_AE_1941500))
 $(eval $(call add_define,ERRATA_A78_AE_1941500))