stm class/intel_th: Updates for 4.10

These are:
   * Fix for an error-path leak in stm
   * Host-driven mode in intel_th
   * Documentation and other small updates
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Merge tag 'stm-for-greg-20161118' of git://git.kernel.org/pub/scm/linux/kernel/git/ash/stm into char-misc-next

Alexander writes:

stm class/intel_th: Updates for 4.10

These are:
  * Fix for an error-path leak in stm
  * Host-driven mode in intel_th
  * Documentation and other small updates

Documentation/trace/intel_th.txt

@@ -97,3 +97,25 @@ $ echo 0 > /sys/bus/intel_th/devices/0-msc0/active
 # and now you can collect the trace from the device node:
 
 $ cat /dev/intel_th0/msc0 > my_stp_trace
+
+Host Debugger Mode
+==================
+
+It is possible to configure the Trace Hub and control its trace
+capture from a remote debug host, which should be connected via one of
+the hardware debugging interfaces, which will then be used to both
+control Intel Trace Hub and transfer its trace data to the debug host.
+
+The driver needs to be told that such an arrangement is taking place
+so that it does not touch any capture/port configuration and avoids
+conflicting with the debug host's configuration accesses. The only
+activity that the driver will perform in this mode is collecting
+software traces to the Software Trace Hub (an stm class device). The
+user is still responsible for setting up adequate master/channel
+mappings that the decoder on the receiving end would recognize.
+
+In order to enable the host mode, set the 'host_mode' parameter of the
+'intel_th' kernel module to 'y'. None of the virtual output devices
+will show up on the intel_th bus. Also, trace configuration and
+capture controlling attribute groups of the 'gth' device will not be
+exposed. The 'sth' device will operate as usual.

Documentation/trace/stm.txt

@@ -69,12 +69,43 @@ stm device's channel mmio region is 64 bytes and hardware page size is
 width==64, you should be able to mmap() one page on this file
 descriptor and obtain direct access to an mmio region for 64 channels.
 
-For kernel-based trace sources, there is "stm_source" device
-class. Devices of this class can be connected and disconnected to/from
-stm devices at runtime via a sysfs attribute.
-
 Examples of STM devices are Intel(R) Trace Hub [1] and Coresight STM
 [2].
 
+stm_source
+==========
+
+For kernel-based trace sources, there is "stm_source" device
+class. Devices of this class can be connected and disconnected to/from
+stm devices at runtime via a sysfs attribute called "stm_source_link"
+by writing the name of the desired stm device there, for example:
+
+$ echo dummy_stm.0 > /sys/class/stm_source/console/stm_source_link
+
+For examples on how to use stm_source interface in the kernel, refer
+to stm_console or stm_heartbeat drivers.
+
+Each stm_source device will need to assume a master and a range of
+channels, depending on how many channels it requires. These are
+allocated for the device according to the policy configuration. If
+there's a node in the root of the policy directory that matches the
+stm_source device's name (for example, "console"), this node will be
+used to allocate master and channel numbers. If there's no such policy
+node, the stm core will pick the first contiguous chunk of channels
+within the first available master. Note that the node must exist
+before the stm_source device is connected to its stm device.
+
+stm_console
+===========
+
+One implementation of this interface also used in the example above is
+the "stm_console" driver, which basically provides a one-way console
+for kernel messages over an stm device.
+
+To configure the master/channel pair that will be assigned to this
+console in the STP stream, create a "console" policy entry (see the
+beginning of this text on how to do that). When initialized, it will
+consume one channel.
+
 [1] https://software.intel.com/sites/default/files/managed/d3/3c/intel-th-developer-manual.pdf
 [2] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0444b/index.html

drivers/hwtracing/intel_th/core.c

@@ -29,6 +29,9 @@
 #include "intel_th.h"
 #include "debug.h"
 
+static bool host_mode __read_mostly;
+module_param(host_mode, bool, 0444);
+
 static DEFINE_IDA(intel_th_ida);
 
 static int intel_th_match(struct device *dev, struct device_driver *driver)
@@ -380,7 +383,7 @@ static void intel_th_device_free(struct intel_th_device *thdev)
 /*
  * Intel(R) Trace Hub subdevices
  */
-static struct intel_th_subdevice {
+static const struct intel_th_subdevice {
 	const char		*name;
 	struct resource		res[3];
 	unsigned		nres;
@@ -527,14 +530,19 @@ static int intel_th_populate(struct intel_th *th, struct resource *devres,
 {
 	struct resource res[3];
 	unsigned int req = 0;
-	int i, err;
+	int src, dst, err;
 
 	/* create devices for each intel_th_subdevice */
-	for (i = 0; i < ARRAY_SIZE(intel_th_subdevices); i++) {
+	for (src = 0, dst = 0; src < ARRAY_SIZE(intel_th_subdevices); src++) {
-		struct intel_th_subdevice *subdev = &intel_th_subdevices[i];
+		const struct intel_th_subdevice *subdev =
+			&intel_th_subdevices[src];
 		struct intel_th_device *thdev;
 		int r;
 
+		/* only allow SOURCE and SWITCH devices in host mode */
+		if (host_mode && subdev->type == INTEL_TH_OUTPUT)
+			continue;
+
 		thdev = intel_th_device_alloc(th, subdev->type, subdev->name,
 					      subdev->id);
 		if (!thdev) {
@@ -577,10 +585,12 @@ static int intel_th_populate(struct intel_th *th, struct resource *devres,
 		}
 
 		if (subdev->type == INTEL_TH_OUTPUT) {
-			thdev->dev.devt = MKDEV(th->major, i);
+			thdev->dev.devt = MKDEV(th->major, dst);
 			thdev->output.type = subdev->otype;
 			thdev->output.port = -1;
 			thdev->output.scratchpad = subdev->scrpd;
+		} else if (subdev->type == INTEL_TH_SWITCH) {
+			thdev->host_mode = host_mode;
 		}
 
 		err = device_add(&thdev->dev);
@@ -597,14 +607,14 @@ static int intel_th_populate(struct intel_th *th, struct resource *devres,
 				req++;
 		}
 
-		th->thdev[i] = thdev;
+		th->thdev[dst++] = thdev;
 	}
 
 	return 0;
 
 kill_subdevs:
-	for (i-- ; i >= 0; i--)
+	for (; dst >= 0; dst--)
-		intel_th_device_remove(th->thdev[i]);
+		intel_th_device_remove(th->thdev[dst]);
 
 	return err;
 }
@@ -717,7 +727,7 @@ void intel_th_free(struct intel_th *th)
 
 	intel_th_request_hub_module_flush(th);
 	for (i = 0; i < TH_SUBDEVICE_MAX; i++)
-		if (th->thdev[i] != th->hub)
+		if (th->thdev[i] && th->thdev[i] != th->hub)
 			intel_th_device_remove(th->thdev[i]);
 
 	intel_th_device_remove(th->hub);

drivers/hwtracing/intel_th/gth.c

@@ -564,6 +564,9 @@ static int intel_th_gth_assign(struct intel_th_device *thdev,
 	struct gth_device *gth = dev_get_drvdata(&thdev->dev);
 	int i, id;
 
+	if (thdev->host_mode)
+		return -EBUSY;
+
 	if (othdev->type != INTEL_TH_OUTPUT)
 		return -EINVAL;
 
@@ -600,6 +603,9 @@ static void intel_th_gth_unassign(struct intel_th_device *thdev,
 	struct gth_device *gth = dev_get_drvdata(&thdev->dev);
 	int port = othdev->output.port;
 
+	if (thdev->host_mode)
+		return;
+
 	spin_lock(&gth->gth_lock);
 	othdev->output.port = -1;
 	othdev->output.active = false;
@@ -654,9 +660,24 @@ static int intel_th_gth_probe(struct intel_th_device *thdev)
 	gth->base = base;
 	spin_lock_init(&gth->gth_lock);
 
+	/*
+	 * Host mode can be signalled via SW means or via SCRPD_DEBUGGER_IN_USE
+	 * bit. Either way, don't reset HW in this case, and don't export any
+	 * capture configuration attributes. Also, refuse to assign output
+	 * drivers to ports, see intel_th_gth_assign().
+	 */
+	if (thdev->host_mode)
+		goto done;
+
 	ret = intel_th_gth_reset(gth);
-	if (ret)
+	if (ret) {
-		return ret;
+		if (ret != -EBUSY)
+			return ret;
+
+		thdev->host_mode = true;
+
+		goto done;
+	}
 
 	for (i = 0; i < TH_CONFIGURABLE_MASTERS + 1; i++)
 		gth->master[i] = -1;
@@ -677,6 +698,7 @@ static int intel_th_gth_probe(struct intel_th_device *thdev)
 		return -ENOMEM;
 	}
 
+done:
 	dev_set_drvdata(dev, gth);
 
 	return 0;

drivers/hwtracing/intel_th/intel_th.h

@@ -54,6 +54,7 @@ struct intel_th_output {
  * @num_resources:	number of resources in @resource array
  * @type:		INTEL_TH_{SOURCE,OUTPUT,SWITCH}
  * @id:			device instance or -1
+ * @host_mode:		Intel TH is controlled by an external debug host
  * @output:		output descriptor for INTEL_TH_OUTPUT devices
  * @name:		device name to match the driver
  */
@@ -64,6 +65,9 @@ struct intel_th_device {
 	unsigned int	type;
 	int		id;
 
+	/* INTEL_TH_SWITCH specific */
+	bool			host_mode;
+
 	/* INTEL_TH_OUTPUT specific */
 	struct intel_th_output	output;
 

drivers/hwtracing/stm/core.c

@@ -361,7 +361,7 @@ static int stm_char_open(struct inode *inode, struct file *file)
 	struct stm_file *stmf;
 	struct device *dev;
 	unsigned int major = imajor(inode);
-	int err = -ENODEV;
+	int err = -ENOMEM;
 
 	dev = class_find_device(&stm_class, NULL, &major, major_match);
 	if (!dev)
@@ -369,8 +369,9 @@ static int stm_char_open(struct inode *inode, struct file *file)
 
 	stmf = kzalloc(sizeof(*stmf), GFP_KERNEL);
 	if (!stmf)
-		return -ENOMEM;
+		goto err_put_device;
 
+	err = -ENODEV;
 	stm_output_init(&stmf->output);
 	stmf->stm = to_stm_device(dev);
 
@@ -382,9 +383,10 @@ static int stm_char_open(struct inode *inode, struct file *file)
 	return nonseekable_open(inode, file);
 
 err_free:
+	kfree(stmf);
+err_put_device:
 	/* matches class_find_device() above */
 	put_device(dev);
-	kfree(stmf);
 
 	return err;
 }