[GIT PULL 17/22] intel_th: msu: Add a sysfs attribute to trigger window switch

[Alexander Shishkin <alexander.shishkin@linux.intel.com>]

Now that we have the means to trigger a window switch for the MSU trace
store, add a sysfs file to allow triggering it from userspace.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
 .../testing/sysfs-bus-intel_th-devices-msc    |  8 ++++++
 drivers/hwtracing/intel_th/msu.c              | 28 +++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-intel_th-devices-msc b/Documentation/ABI/testing/sysfs-bus-intel_th-devices-msc
index b940c5d91cf7..f54ae244f3f1 100644
--- a/Documentation/ABI/testing/sysfs-bus-intel_th-devices-msc
+++ b/Documentation/ABI/testing/sysfs-bus-intel_th-devices-msc
@@ -30,4 +30,12 @@ Description:	(RW) Configure MSC buffer size for "single" or "multi" modes.
 		there are no active users and tracing is not enabled) and then
 		allocates a new one.
 
+What:		/sys/bus/intel_th/devices/<intel_th_id>-msc<msc-id>/win_switch
+Date:		May 2019
+KernelVersion:	5.2
+Contact:	Alexander Shishkin <alexander.shishkin@linux.intel.com>
+Description:	(RW) Trigger window switch for the MSC's buffer, in
+		multi-window mode. In "multi" mode, accepts writes of "1", thereby
+		triggering a window switch for the buffer. Returns an error in any
+		other operating mode or attempts to write something other than "1".
 
diff --git a/drivers/hwtracing/intel_th/msu.c b/drivers/hwtracing/intel_th/msu.c
index 01408a0e2458..089fd1f90a9f 100644
--- a/drivers/hwtracing/intel_th/msu.c
+++ b/drivers/hwtracing/intel_th/msu.c
@@ -1592,10 +1592,38 @@ nr_pages_store(struct device *dev, struct device_attribute *attr,
 
 static DEVICE_ATTR_RW(nr_pages);
 
+static ssize_t
+win_switch_store(struct device *dev, struct device_attribute *attr,
+		 const char *buf, size_t size)
+{
+	struct msc *msc = dev_get_drvdata(dev);
+	unsigned long val;
+	int ret;
+
+	ret = kstrtoul(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	if (val != 1)
+		return -EINVAL;
+
+	mutex_lock(&msc->buf_mutex);
+	if (msc->mode != MSC_MODE_MULTI)
+		ret = -ENOTSUPP;
+	else
+		ret = intel_th_trace_switch(msc->thdev);
+	mutex_unlock(&msc->buf_mutex);
+
+	return ret ? ret : size;
+}
+
+static DEVICE_ATTR_WO(win_switch);
+
 static struct attribute *msc_output_attrs[] = {
 	&dev_attr_wrap.attr,
 	&dev_attr_mode.attr,
 	&dev_attr_nr_pages.attr,
+	&dev_attr_win_switch.attr,
 	NULL,
 };
 
-- 
2.20.1