arm64: cpu_errata: Add capability to advertise Cortex-A73 erratum 858921

In order to work around Cortex-A73 erratum 858921 in a subsequent
patch, add the required capability that advertise the erratum.

As the configuration option it depends on is not present yet,
this has no immediate effect.
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Documentation/arm64/silicon-errata.txt

@@ -54,6 +54,7 @@ stable kernels.
 | ARM            | Cortex-A57      | #852523         | N/A                         |
 | ARM            | Cortex-A57      | #834220         | ARM64_ERRATUM_834220        |
 | ARM            | Cortex-A72      | #853709         | N/A                         |
+| ARM            | Cortex-A73      | #858921         | ARM64_ERRATUM_858921        |
 | ARM            | MMU-500         | #841119,#826419 | N/A                         |
 |                |                 |                 |                             |
 | Cavium         | ThunderX ITS    | #22375, #24313  | CAVIUM_ERRATUM_22375        |

arch/arm64/include/asm/cpucaps.h

@@ -37,7 +37,8 @@
 #define ARM64_HAS_NO_FPSIMD			16
 #define ARM64_WORKAROUND_REPEAT_TLBI		17
 #define ARM64_WORKAROUND_QCOM_FALKOR_E1003	18
+#define ARM64_WORKAROUND_858921			19
 
-#define ARM64_NCAPS				19
+#define ARM64_NCAPS				20
 
 #endif /* __ASM_CPUCAPS_H */

arch/arm64/kernel/cpu_errata.c

@@ -157,6 +157,14 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 			   MIDR_CPU_VAR_REV(0, 0),
 			   MIDR_CPU_VAR_REV(0, 0)),
 	},
+#endif
+#ifdef CONFIG_ARM64_ERRATUM_858921
+	{
+	/* Cortex-A73 all versions */
+		.desc = "ARM erratum 858921",
+		.capability = ARM64_WORKAROUND_858921,
+		MIDR_ALL_VERSIONS(MIDR_CORTEX_A73),
+	},
 #endif
 	{
 	}