[PATCH 1/2] coresight: ete: Always save state on power down

[James Clark]

ETE registers are always system registers so it's highly unlikely there
will be an implementation that preserves them on CPU power down. Also
the ETE DT binding never documented
"arm,coresight-loses-context-with-cpu" so nobody would have legitimately
been able to use that binding to fix it.

Fix it by hard coding the setting for ETE and add a warning if the user
tried to use the module parameter. Don't add a warning if
loses-context-with-cpu is present in the DT as it's not a documented
binding anyway. etm4_init_pm_save() needs to happen after drvdata is
initialised so etm4x_is_ete() can be called.

This fixes the following error when using Coresight with ACPI on the FVP
which supports CPU PM:

  coresight ete0: External agent took claim tag
  WARNING: drivers/hwtracing/coresight/coresight-core.c:248 at coresight_disclaim_device_unlocked+0xe0/0xe8, CPU#0: perf/117

Fixes: 35e1c9163e02 ("coresight: ete: Add support for ETE tracing")
Signed-off-by: James Clark <james.clark at linaro.org>
---
 drivers/hwtracing/coresight/coresight-etm4x-core.c | 41 +++++++++++++++-------
 1 file changed, 29 insertions(+), 12 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index d565a73f0042..a7fb680dd383 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -56,10 +56,11 @@ MODULE_PARM_DESC(boot_enable, "Enable tracing on boot");
 #define PARAM_PM_SAVE_NEVER	  1 /* never save any state */
 #define PARAM_PM_SAVE_SELF_HOSTED 2 /* save self-hosted state only */
 
+/* Save option for ETM4. ETE ignores this option and always saves */
 static int pm_save_enable = PARAM_PM_SAVE_FIRMWARE;
 module_param(pm_save_enable, int, 0444);
 MODULE_PARM_DESC(pm_save_enable,
-	"Save/restore state on power down: 1 = never, 2 = self-hosted");
+	"Save/restore state on power down: 1 = never, 2 = self-hosted. ETM4 only.");
 
 static struct etmv4_drvdata *etmdrvdata[NR_CPUS];
 static void etm4_set_default_config(struct etmv4_config *config);
@@ -1365,6 +1366,30 @@ static void etm4_fixup_wrong_ccitmin(struct etmv4_drvdata *drvdata)
 	}
 }
 
+static int etm4_init_pm_save(struct device *dev, struct etmv4_drvdata *drvdata)
+{
+	if (etm4x_is_ete(drvdata)) {
+		/*
+		 * Always do PM save for ETE. It always uses system registers
+		 * which will be lost on CPU power down.
+		 */
+		pm_save_enable = PARAM_PM_SAVE_SELF_HOSTED;
+	} else if (pm_save_enable == PARAM_PM_SAVE_FIRMWARE) {
+		pm_save_enable = coresight_loses_context_with_cpu(dev) ?
+			PARAM_PM_SAVE_SELF_HOSTED : PARAM_PM_SAVE_NEVER;
+	}
+
+	if (pm_save_enable != PARAM_PM_SAVE_NEVER) {
+		drvdata->save_state = devm_kmalloc(dev,
+						   sizeof(struct etmv4_save_state),
+						   GFP_KERNEL);
+		if (!drvdata->save_state)
+			return -ENOMEM;
+	}
+
+	return 0;
+}
+
 static void etm4_init_arch_data(void *info)
 {
 	u32 etmidr0;
@@ -2247,6 +2272,9 @@ static int etm4_add_coresight_dev(struct etm4_init_arg *init_arg)
 		return -ENOMEM;
 
 	etm4_set_default(&drvdata->config);
+	ret = etm4_init_pm_save(dev, drvdata);
+	if (ret)
+		return ret;
 
 	pdata = coresight_get_platform_data(dev);
 	if (IS_ERR(pdata))
@@ -2305,17 +2333,6 @@ static int etm4_probe(struct device *dev)
 	if (ret)
 		return ret;
 
-	if (pm_save_enable == PARAM_PM_SAVE_FIRMWARE)
-		pm_save_enable = coresight_loses_context_with_cpu(dev) ?
-			       PARAM_PM_SAVE_SELF_HOSTED : PARAM_PM_SAVE_NEVER;
-
-	if (pm_save_enable != PARAM_PM_SAVE_NEVER) {
-		drvdata->save_state = devm_kmalloc(dev,
-				sizeof(struct etmv4_save_state), GFP_KERNEL);
-		if (!drvdata->save_state)
-			return -ENOMEM;
-	}
-
 	raw_spin_lock_init(&drvdata->spinlock);
 
 	drvdata->cpu = coresight_get_cpu(dev);

-- 
2.34.1