DSU: Implement workaround for errata 798953
Under certain near idle conditions, DSU may miss response transfers on
the ACE master or Peripheral port, leading to deadlock. This workaround
disables high-level clock gating of the DSU to prevent this.
Change-Id: I820911d61570bacb38dd325b3519bc8d12caa14b
Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>
diff --git a/lib/cpus/aarch64/dsu_helpers.S b/lib/cpus/aarch64/dsu_helpers.S
index 29870a4..100ffaa 100644
--- a/lib/cpus/aarch64/dsu_helpers.S
+++ b/lib/cpus/aarch64/dsu_helpers.S
@@ -9,6 +9,59 @@
#include <lib/cpus/errata_report.h>
/* -----------------------------------------------------------------------
+ * DSU erratum 798953 check function
+ * Checks the DSU variant, revision and configuration to determine if
+ * the erratum applies. Erratum applies on all configurations of the
+ * DSU and if revision-variant is r0p0.
+ *
+ * The erratum was fixed in r0p1.
+ *
+ * This function is called from both assembly and C environment. So it
+ * follows AAPCS.
+ *
+ * Clobbers: x0-x3
+ * -----------------------------------------------------------------------
+ */
+ .globl check_errata_dsu_798953
+ .globl errata_dsu_798953_wa
+
+func check_errata_dsu_798953
+ mov x2, #ERRATA_APPLIES
+ mov x3, #ERRATA_NOT_APPLIES
+
+ /* Check if DSU is equal to r0p0 */
+ 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, #(0x0 << CLUSTERIDR_REV_SHIFT)
+ cmp x0, x1
+ csel x0, x2, x3, EQ
+ ret
+endfunc check_errata_dsu_798953
+
+ /* --------------------------------------------------
+ * Errata Workaround for DSU erratum #798953.
+ *
+ * Can clobber only: x0-x17
+ * --------------------------------------------------
+ */
+func errata_dsu_798953_wa
+ mov x17, x30
+ bl check_errata_dsu_798953
+ cbz x0, 1f
+
+ /* If erratum applies, disable high-level clock gating */
+ mrs x0, CLUSTERACTLR_EL1
+ orr x0, x0, #CLUSTERACTLR_EL1_DISABLE_CLOCK_GATING
+ msr CLUSTERACTLR_EL1, x0
+ isb
+1:
+ ret x17
+endfunc errata_dsu_798953_wa
+
+ /* -----------------------------------------------------------------------
* DSU erratum 936184 check function
* Checks the DSU variant, revision and configuration to determine if
* the erratum applies. Erratum applies if ACP interface is present