coresight: tmc-etr: Rearrange probing default buffer size

As we are about to refactor the platform specific handling,
make the default buffer size probing generic.
Signed-off-by: NSuzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: NMathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/coresight-tmc.c

@@ -378,6 +378,15 @@ static int tmc_etr_setup_caps(struct device *parent, u32 devid, void *dev_caps)
 	return rc;
 }
 
+static u32 tmc_etr_get_default_buffer_size(struct device *dev)
+{
+	u32 size;
+
+	if (fwnode_property_read_u32(dev->fwnode, "arm,buffer-size", &size))
+		size = SZ_1M;
+	return size;
+}
+
 static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
 {
 	int ret = 0;
@@ -423,16 +432,10 @@ static int tmc_probe(struct amba_device *adev, const struct amba_id *id)
 	/* This device is not associated with a session */
 	drvdata->pid = -1;
 
-	if (drvdata->config_type == TMC_CONFIG_TYPE_ETR) {
-		if (np)
-			ret = of_property_read_u32(np,
-						   "arm,buffer-size",
-						   &drvdata->size);
-		if (ret)
-			drvdata->size = SZ_1M;
-	} else {
+	if (drvdata->config_type == TMC_CONFIG_TYPE_ETR)
+		drvdata->size = tmc_etr_get_default_buffer_size(dev);
+	else
 		drvdata->size = readl_relaxed(drvdata->base + TMC_RSZ) * 4;
-	}
 
 	desc.pdata = pdata;
 	desc.dev = dev;