fix(errata): workaround for Cortex-A510 erratum 2042739

Cortex-A510 erratum 2042739 is a Cat B erratum that applies to revisions
r0p0, r0p1 and r0p2 and is fixed in r0p3.

SDEN can be found here:
https://developer.arm.com/documentation/SDEN2397239

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I1d2ebee3914396e1e298eb45bdab35ce9e194ad9

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

@@ -484,6 +484,10 @@ For Cortex-A510, the following errata build flags are defined :
    Cortex-A510 CPU. This needs to be enabled only for revisions r0p0, r0p1,
    r0p2, r0p3 and r1p0, it is fixed in r1p1.
 
+-  ``ERRATA_A510_2042739``: This applies errata 2042739 workaround to
+   Cortex-A510 CPU. This needs to be enabled only for revisions r0p0, r0p1 and
+   r0p2, it is fixed in r0p3.
+
 DSU Errata Workarounds
 ----------------------
 

include/lib/cpus/aarch64/cortex_a510.h

@@ -13,6 +13,8 @@
  * CPU Extended Control register specific definitions
  ******************************************************************************/
 #define CORTEX_A510_CPUECTLR_EL1				S3_0_C15_C1_4
+#define CORTEX_A510_CPUECTLR_EL1_READPREFERUNIQUE_SHIFT		U(19)
+#define CORTEX_A510_CPUECTLR_EL1_READPREFERUNIQUE_DISABLE	U(1)
 
 /*******************************************************************************
  * CPU Power Control register specific definitions

lib/cpus/aarch64/cortex_a510.S

@@ -80,6 +80,36 @@ func check_errata_2288014
 	b	cpu_rev_var_ls
 endfunc check_errata_2288014
 
+	/* --------------------------------------------------
+	 * Errata Workaround for Cortex-A510 Errata #2042739.
+	 * This applies only to revisions r0p0, r0p1 and r0p2.
+	 * (fixed in r0p3)
+	 * x0: variant[4:7] and revision[0:3] of current cpu.
+	 * Shall clobber: x0, x1, x17
+	 * --------------------------------------------------
+	 */
+func errata_cortex_a510_2042739_wa
+	/* Check workaround compatibility. */
+	mov	x17, x30
+	bl	check_errata_2042739
+	cbz	x0, 1f
+
+	/* Apply the workaround by disabling ReadPreferUnique. */
+	mrs	x0, CORTEX_A510_CPUECTLR_EL1
+	mov	x1, #CORTEX_A510_CPUECTLR_EL1_READPREFERUNIQUE_DISABLE
+	bfi	x0, x1, #CORTEX_A510_CPUECTLR_EL1_READPREFERUNIQUE_SHIFT, #1
+	msr	CORTEX_A510_CPUECTLR_EL1, x0
+
+1:
+	ret	x17
+endfunc errata_cortex_a510_2042739_wa
+
+func check_errata_2042739
+	/* Applies to revisions r0p0 - r0p2 */
+	mov	x1, #0x02
+	b	cpu_rev_var_ls
+endfunc check_errata_2042739
+
 	/* ----------------------------------------------------
 	 * HW will do the cache maintenance while powering down
 	 * ----------------------------------------------------
@@ -112,6 +142,7 @@ func cortex_a510_errata_report
 	 */
 	report_errata ERRATA_A510_1922240, cortex_a510, 1922240
 	report_errata ERRATA_A510_2288014, cortex_a510, 2288014
+	report_errata ERRATA_A510_2042739, cortex_a510, 2042739
 
 	ldp	x8, x30, [sp], #16
 	ret
@@ -139,6 +170,11 @@ func cortex_a510_reset_func
 	bl	errata_cortex_a510_2288014_wa
 #endif
 
+#if ERRATA_A510_2042739
+	mov	x0, x18
+	bl	errata_cortex_a510_2042739_wa
+#endif
+
 	ret	x19
 endfunc cortex_a510_reset_func
 

lib/cpus/cpu-ops.mk

@@ -539,6 +539,10 @@ ERRATA_A510_1922240	?=0
 # fixed in r1p1.
 ERRATA_A510_2288014	?=0
 
+# Flag to apply erratum 2042739 workaround during reset. This erratum applies
+# to revisions r0p0, r0p1 and r0p2 of the Cortex-A510 cpu and is fixed in r0p3.
+ERRATA_A510_2042739	?=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
@@ -1004,6 +1008,10 @@ $(eval $(call add_define,ERRATA_A510_1922240))
 $(eval $(call assert_boolean,ERRATA_A510_2288014))
 $(eval $(call add_define,ERRATA_A510_2288014))
 
+# Process ERRATA_A510_2042739 flag
+$(eval $(call assert_boolean,ERRATA_A510_2042739))
+$(eval $(call add_define,ERRATA_A510_2042739))
+
 # Process ERRATA_DSU_798953 flag
 $(eval $(call assert_boolean,ERRATA_DSU_798953))
 $(eval $(call add_define,ERRATA_DSU_798953))