DSU erratum 936184 workaround
If the system is in near idle conditions, this erratum could cause a
deadlock or data corruption. This patch applies the workaround that
prevents this.
This DSU erratum affects only the DSUs that contain the ACP interface
and it was fixed in r2p0. The workaround is applied only to the DSUs
that are actually affected.
Link to respective Arm documentation:
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.epm138168/index.html
Change-Id: I033213b3077685130fc1e3f4f79c4d15d7483ec9
Signed-off-by: John Tsichritzis <john.tsichritzis@arm.com>
diff --git a/lib/cpus/aarch64/dsu_helpers.S b/lib/cpus/aarch64/dsu_helpers.S
new file mode 100644
index 0000000..293ed24
--- /dev/null
+++ b/lib/cpus/aarch64/dsu_helpers.S
@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <asm_macros.S>
+#include <dsu_def.h>
+#include <errata_report.h>
+
+/*
+ * DSU erratum 936184
+ * Check the DSU variant, revision and configuration to determine if the
+ * erratum applies. This erratum was fixed in r2p0.
+ *
+ * This function is called from both assembly and C environment. So it
+ * follows AAPCS.
+ *
+ * Clobbers: x0-x3
+ */
+ .globl check_errata_dsu_936184
+ .globl errata_dsu_936184_wa
+
+func check_errata_dsu_936184
+ mov x2, #ERRATA_NOT_APPLIES
+ mov x3, #ERRATA_APPLIES
+
+ /* Erratum applies only if ACP interface is present in DSU */
+ mov x0, x2
+ mrs x1, CLUSTERCFR_EL1
+ ubfx x1, x1, #CLUSTERCFR_ACP_SHIFT, #1
+ cbz x1, 1f
+
+ /* If ACP is present, check if DSU is older than r2p0 */
+ mrs x1, CLUSTERIDR_EL1
+
+ /* DSU variant and revision bitfields in CLUSTERIDR are adjacent */
+ ubfx x0, x1, #CLUSTERIDR_REV_SHIFT,\
+ #(CLUSTERIDR_REV_BITS + CLUSTERIDR_VAR_BITS)
+ mov x1, #(0x2 << CLUSTERIDR_REV_BITS)
+ cmp x0, x1
+ csel x0, x2, x3, hs
+1:
+ ret
+endfunc check_errata_dsu_936184
+
+func errata_dsu_936184_wa
+ mov x20, x30
+ bl check_errata_dsu_936184
+ cbz x0, 1f
+
+ /* If erratum applies, we set a mask to a DSU control register */
+ mrs x0, CLUSTERACTLR_EL1
+ ldr x1, =DSU_ERRATA_936184_MASK
+ orr x0, x0, x1
+ msr CLUSTERACTLR_EL1, x0
+ isb
+1:
+ ret x20
+endfunc errata_dsu_936184_wa