errata: workaround for Neoverse V1 errata 1940577

Neoverse V1 erratum 1940577 is a Cat B erratum, present in some
revisions of the V1 processor core.  The workaround is to insert a
DMB ST before acquire atomic instructions without release semantics.
This issue is present in revisions r0p0 - r1p1  but this workaround
only applies to revisions r1p0 - r1p1, there is no workaround for older
versions.

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

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I210ad7d8f31c81b6ac51b028dfbce75a725c11aa

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

@@ -329,6 +329,10 @@ 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_1940577``: This applies errata 1940577 workaround to Neoverse-V1
+   CPU. This needs to be enabled only for revision r1p0 and r1p1 of the
+   CPU.
+
 DSU Errata Workarounds
 ----------------------
 

lib/cpus/aarch64/neoverse_v1.S

@@ -49,6 +49,61 @@ func check_errata_1791573
 	b	cpu_rev_var_ls
 endfunc check_errata_1791573
 
+	/* --------------------------------------------------
+	 * Errata Workaround for Neoverse V1 Erratum #1940577
+	 * This applies to revisions r1p0 - r1p1 and is open.
+	 * It 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_neoverse_v1_1940577_wa
+	/* Compare x0 against revisions r1p0 - r1p1 */
+	mov	x17, x30
+	bl	check_errata_1940577
+	cbz	x0, 1f
+
+	mov	x0, #0
+	msr	S3_6_C15_C8_0, x0
+	ldr	x0, =0x10E3900002
+	msr	S3_6_C15_C8_2, x0
+	ldr	x0, =0x10FFF00083
+	msr	S3_6_C15_C8_3, x0
+	ldr	x0, =0x2001003FF
+	msr	S3_6_C15_C8_1, x0
+
+	mov	x0, #1
+	msr	S3_6_C15_C8_0, x0
+	ldr	x0, =0x10E3800082
+	msr	S3_6_C15_C8_2, x0
+	ldr	x0, =0x10FFF00083
+	msr	S3_6_C15_C8_3, x0
+	ldr	x0, =0x2001003FF
+	msr	S3_6_C15_C8_1, x0
+
+	mov	x0, #2
+	msr	S3_6_C15_C8_0, x0
+	ldr	x0, =0x10E3800200
+	msr	S3_6_C15_C8_2, x0
+	ldr	x0, =0x10FFF003E0
+	msr	S3_6_C15_C8_3, x0
+	ldr	x0, =0x2001003FF
+	msr	S3_6_C15_C8_1, x0
+
+	isb
+1:
+	ret	x17
+endfunc errata_neoverse_v1_1940577_wa
+
+func check_errata_1940577
+	/* Applies to revisions r1p0 - r1p1. */
+	mov	x1, #0x10
+	mov	x2, #0x11
+	b	cpu_rev_var_range
+endfunc check_errata_1940577
+
 	/* ---------------------------------------------
 	 * HW will do the cache maintenance while powering down
 	 * ---------------------------------------------
@@ -80,6 +135,7 @@ func neoverse_v1_errata_report
 	 * checking functions of each errata.
 	 */
 	report_errata ERRATA_V1_1791573, neoverse_v1, 1791573
+	report_errata ERRATA_V1_1940577, neoverse_v1, 1940577
 
 	ldp	x8, x30, [sp], #16
 	ret
@@ -98,6 +154,11 @@ func neoverse_v1_reset_func
 	bl	errata_neoverse_v1_1791573_wa
 #endif
 
+#if ERRATA_V1_1940577
+	mov	x0, x18
+	bl	errata_neoverse_v1_1940577_wa
+#endif
+
 	ret	x19
 endfunc neoverse_v1_reset_func
 

lib/cpus/cpu-ops.mk

@@ -376,6 +376,10 @@ ERRATA_N1_1946160	?=0
 # to revisions r0p0 and r1p0 of the Neoverse V1 core, and was fixed in r1p1.
 ERRATA_V1_1791573	?=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
+
 # Flag to apply DSU erratum 798953. This erratum applies to DSUs revision r0p0.
 # Applying the workaround results in higher DSU power consumption on idle.
 ERRATA_DSU_798953	?=0
@@ -685,6 +689,10 @@ $(eval $(call add_define,ERRATA_N1_1946160))
 $(eval $(call assert_boolean,ERRATA_V1_1791573))
 $(eval $(call add_define,ERRATA_V1_1791573))
 
+# Process ERRATA_V1_1940577 flag
+$(eval $(call assert_boolean,ERRATA_V1_1940577))
+$(eval $(call add_define,ERRATA_V1_1940577))
+
 # Process ERRATA_DSU_798953 flag
 $(eval $(call assert_boolean,ERRATA_DSU_798953))
 $(eval $(call add_define,ERRATA_DSU_798953))