[PATCH v1 01/11] coresight: etm4x: Control the trace unit in CPU suspend

[Leo Yan]

If a trace unit has been enabled, a CPU suspend operation misses to
disable the trace unit.  After the CPU resumes, it also does not follow
the general flow for re-enabling the trace unit.  As a result, this may
lead to a wrong state machine for the ETM.

This commit stops the trace unit during the CPU suspend flow and
re-enables the trace unit in the resume flow.

Fixes: f188b5e76aae ("coresight: etm4x: Save/restore state across CPU low power states")
Signed-off-by: Leo Yan <leo.yan at arm.com>
---
 drivers/hwtracing/coresight/coresight-etm4x-core.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index 6a5898355a83..b12d59b89a49 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -1820,6 +1820,11 @@ static int __etm4_cpu_save(struct etmv4_drvdata *drvdata)
 	state = drvdata->save_state;
 
 	state->trcprgctlr = etm4x_read32(csa, TRCPRGCTLR);
+
+	/* Stop the trace unit if it is enabled */
+	if (state->trcprgctlr)
+		etm4_disable_trace_unit(drvdata);
+
 	if (drvdata->nr_pe)
 		state->trcprocselr = etm4x_read32(csa, TRCPROCSELR);
 	state->trcconfigr = etm4x_read32(csa, TRCCONFIGR);
@@ -1951,7 +1956,6 @@ static void __etm4_cpu_restore(struct etmv4_drvdata *drvdata)
 	etm4_cs_unlock(drvdata, csa);
 	etm4x_relaxed_write32(csa, state->trcclaimset, TRCCLAIMSET);
 
-	etm4x_relaxed_write32(csa, state->trcprgctlr, TRCPRGCTLR);
 	if (drvdata->nr_pe)
 		etm4x_relaxed_write32(csa, state->trcprocselr, TRCPROCSELR);
 	etm4x_relaxed_write32(csa, state->trcconfigr, TRCCONFIGR);
@@ -2035,6 +2039,15 @@ static void __etm4_cpu_restore(struct etmv4_drvdata *drvdata)
 
 	/* Unlock the OS lock to re-enable trace and external debug access */
 	etm4_os_unlock(drvdata);
+
+	/*
+	 * Re-enable the trace unit if it was enabled before suspend.
+	 * Put it after etm4_os_unlock() as unlocking the OS lock is the
+	 * prerequisite for enabling the trace unit.
+	 */
+	if (state->trcprgctlr)
+		etm4_enable_trace_unit(drvdata);
+
 	etm4_cs_lock(drvdata, csa);
 }
 
-- 
2.34.1