fix(errata): workaround for Cortex X2 erratum 2002765

Cortex X2 erratum 2002765 is a Cat B erratum present in the X2 core.
It applies to revisions r0p0, r1p0, and r2p0 and is still open.

SDEN can be found here:
https://developer.arm.com/documentation/SDEN1775100

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I11576a03bfd8a6b1bd9ffef4430a097d763ca3cf

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

@@ -443,6 +443,10 @@ For Neoverse N2, the following errata build flags are defined :
 
 For Cortex-X2, the following errata build flags are defined :
 
+-  ``ERRATA_X2_2002765``: This applies errata 2002765 workaround to Cortex-X2
+   CPU. This needs to be enabled for revisions r0p0, r1p0, and r2p0 of the CPU,
+   it is still open.
+
 -  ``ERRATA_X2_2083908``: This applies errata 2083908 workaround to Cortex-X2
    CPU. This needs to be enabled for revision r2p0 of the CPU, it is still open.
 

lib/cpus/aarch64/cortex_x2.S

@@ -21,6 +21,40 @@
 #error "Cortex X2 supports only AArch64. Compile with CTX_INCLUDE_AARCH32_REGS=0"
 #endif
 
+	/* --------------------------------------------------
+	 * Errata Workaround for Cortex X2 Errata #2002765.
+	 * This applies to revisions r0p0, r1p0, and r2p0 and
+	 * is open.
+	 * x0: variant[4:7] and revision[0:3] of current cpu.
+	 * Shall clobber: x0, x1, x17
+	 * --------------------------------------------------
+	 */
+func errata_cortex_x2_2002765_wa
+	/* Check workaround compatibility. */
+	mov	x17, x30
+	bl	check_errata_2002765
+	cbz	x0, 1f
+
+	ldr	x0, =0x6
+	msr	S3_6_C15_C8_0, x0 /* CPUPSELR_EL3 */
+	ldr	x0, =0xF3A08002
+	msr	S3_6_C15_C8_2, x0 /* CPUPOR_EL3 */
+	ldr	x0, =0xFFF0F7FE
+	msr	S3_6_C15_C8_3, x0 /* CPUPMR_EL3 */
+	ldr	x0, =0x40000001003ff
+	msr	S3_6_C15_C8_1, x0 /* CPUPCR_EL3 */
+	isb
+
+1:
+	ret	x17
+endfunc errata_cortex_x2_2002765_wa
+
+func check_errata_2002765
+	/* Applies to r0p0 - r2p0 */
+	mov	x1, #0x20
+	b	cpu_rev_var_ls
+endfunc check_errata_2002765
+
 	/* --------------------------------------------------
 	 * Errata Workaround for Cortex X2 Errata #2083908.
 	 * This applies to revision r2p0 and is open.
@@ -80,6 +114,7 @@ func cortex_x2_errata_report
 	 * Report all errata. The revision-variant information is passed to
 	 * checking functions of each errata.
 	 */
+	report_errata ERRATA_X2_2002765, cortex_x2, 2002765
 	report_errata ERRATA_X2_2083908, cortex_x2, 2083908
 
 	ldp	x8, x30, [sp], #16
@@ -98,6 +133,11 @@ func cortex_x2_reset_func
 	bl	cpu_get_rev_var
 	mov	x18, x0
 
+#if ERRATA_X2_2002765
+	mov	x0, x18
+	bl	errata_cortex_x2_2002765_wa
+#endif
+
 #if ERRATA_X2_2083908
 	mov	x0, x18
 	bl	errata_cortex_x2_2083908_wa

lib/cpus/cpu-ops.mk

@@ -495,6 +495,10 @@ ERRATA_A710_2055002	?=0
 # to revision r0p0, r1p0 and r2p0 of the Cortex-A710 cpu and is still open.
 ERRATA_A710_2017096	?=0
 
+# Flag to apply erratum 2002765 workaround during reset. This erratum applies
+# to revisions r0p0, r1p0, and r2p0 of the Cortex-X2 cpu and is still open.
+ERRATA_X2_2002765   ?=0
+
 # Flag to apply erratum 2083908 workaround during reset. This erratum applies
 # to revision r2p0 of the Cortex-X2 cpu and is still open.
 ERRATA_X2_2083908   ?=0
@@ -924,6 +928,10 @@ $(eval $(call add_define,ERRATA_A710_2055002))
 $(eval $(call assert_boolean,ERRATA_A710_2017096))
 $(eval $(call add_define,ERRATA_A710_2017096))
 
+# Process ERRATA_X2_2002765 flag
+$(eval $(call assert_boolean,ERRATA_X2_2002765))
+$(eval $(call add_define,ERRATA_X2_2002765))
+
 # Process ERRATA_X2_2083908 flag
 $(eval $(call assert_boolean,ERRATA_X2_2083908))
 $(eval $(call add_define,ERRATA_X2_2083908))