errata: workaround for Neoverse V1 errata 1925756

Neoverse V1 erratum 1925756 is a Cat B erratum present in r0p0, r1p0,
and r1p1 of the V1 processor core, and it is still open.

SDEN can be found here:
https://documentation-service.arm.com/static/60d499080320e92fa40b4625

Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>
Change-Id: I6500dc98da92a7c405b9ae09d794d666e8f4ae52

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

@@ -337,6 +337,9 @@ For Neoverse V1, the following errata build flags are defined :
    CPU. This needs to be enabled only for revisions r0p0 and r1p0, it is fixed
    in r1p1.
 
+-  ``ERRATA_V1_1925756``: This applies errata 1925756 workaround to Neoverse-V1
+   CPU. This needs to be enabled for r0p0, r1p0, and r1p1, it is still open.
+
 -  ``ERRATA_V1_1940577``: This applies errata 1940577 workaround to Neoverse-V1
    CPU. This needs to be enabled only for revision r1p0 and r1p1 of the
    CPU.

include/lib/cpus/aarch64/neoverse_v1.h

@@ -13,6 +13,7 @@
  * CPU Extended Control register specific definitions.
  ******************************************************************************/
 #define NEOVERSE_V1_CPUECTLR_EL1				S3_0_C15_C1_4
+#define NEOVERSE_V1_CPUECTLR_EL1_BIT_8				(ULL(1) << 8)
 #define NEOVERSE_V1_CPUECTLR_EL1_BIT_53				(ULL(1) << 53)
 
 /*******************************************************************************

lib/cpus/aarch64/neoverse_v1.S

@@ -105,6 +105,34 @@ func check_errata_1852267
 	b	cpu_rev_var_ls
 endfunc check_errata_1852267
 
+	/* --------------------------------------------------
+	 * Errata Workaround for Neoverse V1 Errata #1925756.
+	 * This applies to revisions <= r1p1.
+	 * x0: variant[4:7] and revision[0:3] of current cpu.
+	 * Shall clobber: x0-x17
+	 * --------------------------------------------------
+	 */
+func errata_neoverse_v1_1925756_wa
+	/* Check workaround compatibility. */
+	mov	x17, x30
+	bl	check_errata_1925756
+	cbz	x0, 1f
+
+	/* Set bit 8 in CPUECTLR_EL1 */
+	mrs	x1, NEOVERSE_V1_CPUECTLR_EL1
+	orr	x1, x1, #NEOVERSE_V1_CPUECTLR_EL1_BIT_8
+	msr	NEOVERSE_V1_CPUECTLR_EL1, x1
+	isb
+1:
+	ret	x17
+endfunc errata_neoverse_v1_1925756_wa
+
+func check_errata_1925756
+	/* Applies to <= r1p1. */
+	mov	x1, #0x11
+	b	cpu_rev_var_ls
+endfunc check_errata_1925756
+
 	/* --------------------------------------------------
 	 * Errata Workaround for Neoverse V1 Erratum #1940577
 	 * This applies to revisions r1p0 - r1p1 and is open.
@@ -193,6 +221,7 @@ func neoverse_v1_errata_report
 	report_errata ERRATA_V1_1774420, neoverse_v1, 1774420
 	report_errata ERRATA_V1_1791573, neoverse_v1, 1791573
 	report_errata ERRATA_V1_1852267, neoverse_v1, 1852267
+	report_errata ERRATA_V1_1925756, neoverse_v1, 1925756
 	report_errata ERRATA_V1_1940577, neoverse_v1, 1940577
 
 	ldp	x8, x30, [sp], #16
@@ -222,6 +251,11 @@ func neoverse_v1_reset_func
 	bl	errata_neoverse_v1_1852267_wa
 #endif
 
+#if ERRATA_V1_1925756
+	mov	x0, x18
+	bl	errata_neoverse_v1_1925756_wa
+#endif
+
 #if ERRATA_V1_1940577
 	mov	x0, x18
 	bl	errata_neoverse_v1_1940577_wa

lib/cpus/cpu-ops.mk

@@ -384,6 +384,10 @@ ERRATA_V1_1791573	?=0
 # to revisions r0p0 and r1p0 of the Neoverse V1 core, and was fixed in r1p1.
 ERRATA_V1_1852267	?=0
 
+# Flag to apply erratum 1925756 workaround during reset.  This needs to be
+# enabled for r0p0, r1p0, and r1p1 of the Neoverse V1 core, it is still open.
+ERRATA_V1_1925756	?=0
+
 # Flag to apply erratum 1940577 workaround during reset. This erratum applies
 # to revisions r1p0 and r1p1 of the Neoverse V1 cpu.
 ERRATA_V1_1940577	?=0
@@ -705,6 +709,10 @@ $(eval $(call add_define,ERRATA_V1_1791573))
 $(eval $(call assert_boolean,ERRATA_V1_1852267))
 $(eval $(call add_define,ERRATA_V1_1852267))
 
+# Process ERRATA_V1_1925756 flag
+$(eval $(call assert_boolean,ERRATA_V1_1925756))
+$(eval $(call add_define,ERRATA_V1_1925756))
+
 # Process ERRATA_V1_1940577 flag
 $(eval $(call assert_boolean,ERRATA_V1_1940577))
 $(eval $(call add_define,ERRATA_V1_1940577))