coresight: tmc-etr: Handle memory errors

We have so far ignored the memory errors, assuming that we have perfect
hardware and driver. Let us handle the memory errors reported by the
TMC ETR in status and truncate the buffer.

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
[Removed ASCII smiley face from changelog]
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20190829202842.580-6-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/coresight-tmc-etr.c

@@ -928,6 +928,19 @@ static void tmc_sync_etr_buf(struct tmc_drvdata *drvdata)
 	rrp = tmc_read_rrp(drvdata);
 	rwp = tmc_read_rwp(drvdata);
 	status = readl_relaxed(drvdata->base + TMC_STS);
+
+	/*
+	 * If there were memory errors in the session, truncate the
+	 * buffer.
+	 */
+	if (WARN_ON_ONCE(status & TMC_STS_MEMERR)) {
+		dev_dbg(&drvdata->csdev->dev,
+			"tmc memory error detected, truncating buffer\n");
+		etr_buf->len = 0;
+		etr_buf->full = 0;
+		return;
+	}
+
 	etr_buf->full = status & TMC_STS_FULL;
 
 	WARN_ON(!etr_buf->ops || !etr_buf->ops->sync);

drivers/hwtracing/coresight/coresight-tmc.h

@@ -47,6 +47,7 @@
 #define TMC_STS_TMCREADY_BIT	2
 #define TMC_STS_FULL		BIT(0)
 #define TMC_STS_TRIGGERED	BIT(1)
+#define TMC_STS_MEMERR		BIT(5)
 /*
  * TMC_AXICTL - 0x110
  *