fix(errata): workaround for Cortex X2 erratum 2058056

Cortex X2 erratum 2058056 is a Cat B erratum present in the X2 core.
It applies to revisions r0p0, r1p0, and r2p0 and is still open.

There are 2 ways this workaround can be accomplished, the first of
which involves executing a few additional instructions around MSR
writes to CPUECTLR when disabling the prefetcher. (see SDEN for
details)

However, this patch implements the 2nd possible workaround which sets
the prefetcher into its most conservative mode, since this workaround
is generic.

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

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: Idb20d9928c986616cd5bedf40bb29d46d384cfd3

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

@@ -447,6 +447,10 @@ For Cortex-X2, the following errata build flags are defined :
    CPU. This needs to be enabled for revisions r0p0, r1p0, and r2p0 of the CPU,
    it is still open.
 
+-  ``ERRATA_X2_2058056``: This applies errata 2058056 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.
 

include/lib/cpus/aarch64/cortex_x2.h

@@ -14,6 +14,15 @@
  ******************************************************************************/
 #define CORTEX_X2_CPUECTLR_EL1					S3_0_C15_C1_4
 
+/*******************************************************************************
+ * CPU Extended Control register 2 specific definitions
+ ******************************************************************************/
+#define CORTEX_X2_CPUECTLR2_EL1					S3_0_C15_C1_5
+
+#define CORTEX_X2_CPUECTLR2_EL1_PF_MODE_SHIFT			U(11)
+#define CORTEX_X2_CPUECTLR2_EL1_PF_MODE_WIDTH			U(4)
+#define CORTEX_X2_CPUECTLR2_EL1_PF_MODE_CNSRV			ULL(0x9)
+
 /*******************************************************************************
  * CPU Power Control register specific definitions
  ******************************************************************************/

lib/cpus/aarch64/cortex_x2.S

@@ -55,6 +55,35 @@ func check_errata_2002765
 	b	cpu_rev_var_ls
 endfunc check_errata_2002765
 
+	/* --------------------------------------------------
+	 * Errata Workaround for Cortex X2 Errata #2058056.
+	 * 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_2058056_wa
+	/* Check workaround compatibility. */
+	mov	x17, x30
+	bl	check_errata_2058056
+	cbz	x0, 1f
+
+	mrs	x1, CORTEX_X2_CPUECTLR2_EL1
+	mov	x0, #CORTEX_X2_CPUECTLR2_EL1_PF_MODE_CNSRV
+	bfi	x1, x0, #CORTEX_X2_CPUECTLR2_EL1_PF_MODE_SHIFT, #CORTEX_X2_CPUECTLR2_EL1_PF_MODE_WIDTH
+	msr	CORTEX_X2_CPUECTLR2_EL1, x1
+
+1:
+	ret	x17
+endfunc errata_cortex_x2_2058056_wa
+
+func check_errata_2058056
+	/* Applies to r0p0 - r2p0 */
+	mov	x1, #0x20
+	b	cpu_rev_var_ls
+endfunc check_errata_2058056
+
 	/* --------------------------------------------------
 	 * Errata Workaround for Cortex X2 Errata #2083908.
 	 * This applies to revision r2p0 and is open.
@@ -115,6 +144,7 @@ func cortex_x2_errata_report
 	 * checking functions of each errata.
 	 */
 	report_errata ERRATA_X2_2002765, cortex_x2, 2002765
+	report_errata ERRATA_X2_2058056, cortex_x2, 2058056
 	report_errata ERRATA_X2_2083908, cortex_x2, 2083908
 
 	ldp	x8, x30, [sp], #16
@@ -138,6 +168,11 @@ func cortex_x2_reset_func
 	bl	errata_cortex_x2_2002765_wa
 #endif
 
+#if ERRATA_X2_2058056
+	mov	x0, x18
+	bl	errata_cortex_x2_2058056_wa
+#endif
+
 #if ERRATA_X2_2083908
 	mov	x0, x18
 	bl	errata_cortex_x2_2083908_wa

lib/cpus/cpu-ops.mk

@@ -499,6 +499,10 @@ ERRATA_A710_2017096	?=0
 # to revisions r0p0, r1p0, and r2p0 of the Cortex-X2 cpu and is still open.
 ERRATA_X2_2002765   ?=0
 
+# Flag to apply erratum 2058056 workaround during reset. This erratum applies
+# to revisions r0p0, r1p0, and r2p0 of the Cortex-X2 cpu and is still open.
+ERRATA_X2_2058056   ?=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
@@ -932,6 +936,10 @@ $(eval $(call add_define,ERRATA_A710_2017096))
 $(eval $(call assert_boolean,ERRATA_X2_2002765))
 $(eval $(call add_define,ERRATA_X2_2002765))
 
+# Process ERRATA_X2_2058056 flag
+$(eval $(call assert_boolean,ERRATA_X2_2058056))
+$(eval $(call add_define,ERRATA_X2_2058056))
+
 # Process ERRATA_X2_2083908 flag
 $(eval $(call assert_boolean,ERRATA_X2_2083908))
 $(eval $(call add_define,ERRATA_X2_2083908))