Revert workaround for Neoverse N1 erratum 1800710

This reverts commit 11af40b6, reversing
changes made to 2afcf1d4.

This errata workaround did not work as intended so we are reverting this
change.  In the future, when the corrected workaround is published in an
SDEN, we will push a new workaround.

This is the patch being reverted:
https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/4750

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I20aa064c1bac9671939e657bec269d32b9e75a97

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

@@ -278,9 +278,6 @@ For Neoverse N1, the following errata build flags are defined :
 -  ``ERRATA_N1_1542419``: This applies errata 1542419 workaround to Neoverse-N1
    CPU. This needs to be enabled only for revisions r3p0 - r4p0 of the CPU.
 
--  ``ERRATA_N1_1800710``: This applies errata 1800710 workaround to Neoverse-N1
-   CPU. This needs to be enabled only for revisions <= r4p0 of the CPU.
-
 DSU Errata Workarounds
 ----------------------
 

include/lib/cpus/aarch64/neoverse_n1.h

@@ -35,7 +35,6 @@
 
 #define NEOVERSE_N1_WS_THR_L2_MASK	(ULL(3) << 24)
 #define NEOVERSE_N1_CPUECTLR_EL1_MM_TLBPF_DIS_BIT	(ULL(1) << 51)
-#define NEOVERSE_N1_CPUECTLR_EL1_BIT_53			(ULL(1) << 53)
 #define NEOVERSE_N1_CPUECTLR_EL1_EXTLLC_BIT		(ULL(1) << 0)
 
 /*******************************************************************************

lib/cpus/aarch64/neoverse_n1.S

@@ -375,35 +375,6 @@ func check_errata_1542419
 	b	cpu_rev_var_range
 endfunc check_errata_1542419
 
-/* --------------------------------------------------
- * Errata Workaround for Neoverse N1 Erratum 1800710.
- * This applies to revisions <= r4p0 of Neoverse N1
- * Inputs:
- * x0: variant[4:7] and revision[0:3] of current cpu.
- * Shall clobber: x0-x17
- * --------------------------------------------------
- */
-func errata_n1_1800710_wa
-	/* Compare x0 against revision <= r4p0 */
-	mov	x17, x30
-	bl	check_errata_1800710
-	cbz	x0, 1f
-
-	/* Disable allocation of splintered pages in the L2 TLB */
-	mrs	x1, NEOVERSE_N1_CPUECTLR_EL1
-	orr	x1, x1, NEOVERSE_N1_CPUECTLR_EL1_BIT_53
-	msr	NEOVERSE_N1_CPUECTLR_EL1, x1
-	isb
-1:
-	ret	x17
-endfunc errata_n1_1800710_wa
-
-func check_errata_1800710
-	/* Applies to everything <= r4p0 */
-	mov	x1, #0x40
-	b	cpu_rev_var_ls
-endfunc check_errata_1800710
-
 func neoverse_n1_reset_func
 	mov	x19, x30
 
@@ -478,11 +449,6 @@ func neoverse_n1_reset_func
 	bl	errata_n1_1542419_wa
 #endif
 
-#if ERRATA_N1_1800710
-	mov	x0, x18
-	bl	errata_n1_1800710_wa
-#endif
-
 #if ENABLE_AMU
 	/* Make sure accesses from EL0/EL1 and EL2 are not trapped to EL3 */
 	mrs	x0, actlr_el3
@@ -556,7 +522,6 @@ func neoverse_n1_errata_report
 	report_errata ERRATA_N1_1275112, neoverse_n1, 1275112
 	report_errata ERRATA_N1_1315703, neoverse_n1, 1315703
 	report_errata ERRATA_N1_1542419, neoverse_n1, 1542419
-	report_errata ERRATA_N1_1800710, neoverse_n1, 1800710
 	report_errata ERRATA_DSU_936184, neoverse_n1, dsu_936184
 
 	ldp	x8, x30, [sp], #16

lib/cpus/cpu-ops.mk

@@ -314,10 +314,6 @@ ERRATA_N1_1315703	?=0
 # to revisions r3p0 - r4p0 of the Neoverse N1 cpu.
 ERRATA_N1_1542419	?=0
 
-# Flag to apply erratum 1800710 workaround during reset. This erratum applies
-# to revisions <= r4p0 of the Neoverse N1 cpu.
-ERRATA_N1_1800710	?=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
@@ -567,10 +563,6 @@ $(eval $(call add_define,ERRATA_N1_1315703))
 $(eval $(call assert_boolean,ERRATA_N1_1542419))
 $(eval $(call add_define,ERRATA_N1_1542419))
 
-# Process ERRATA_N1_1800710 flag
-$(eval $(call assert_boolean,ERRATA_N1_1800710))
-$(eval $(call add_define,ERRATA_N1_1800710))
-
 # Process ERRATA_DSU_798953 flag
 $(eval $(call assert_boolean,ERRATA_DSU_798953))
 $(eval $(call add_define,ERRATA_DSU_798953))