drm/i915/guc: Split relay control and GuC log level

Those two concepts are really separate. Since GuC is writing data into
its own buffer and we even provide a way for userspace to read directly
from it using i915_guc_log_dump debugfs, there's no real reason to tie
log level with relay creation.
Let's create a separate debugfs, giving userspace a way to create a
relay on demand, when it wants to read a continuous log rather than a
snapshot.

v2: Don't touch guc_log_level on relay creation error, adjust locking
    after rebase, s/dev_priv/i915, pass guc to file->private_data (Sagar)
    Use struct_mutex rather than runtime.lock for set_log_level
v3: Tidy ordering of definitions (Sagar)

Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180319095348.9716-5-michal.winiarski@intel.com

drivers/gpu/drm/i915/i915_debugfs.c

@@ -2495,32 +2495,73 @@ static int i915_guc_log_dump(struct seq_file *m, void *data)
 	return 0;
 }
 
-static int i915_guc_log_control_get(void *data, u64 *val)
+static int i915_guc_log_level_get(void *data, u64 *val)
 {
 	struct drm_i915_private *dev_priv = data;
 
 	if (!USES_GUC(dev_priv))
 		return -ENODEV;
 
-	*val = intel_guc_log_control_get(&dev_priv->guc.log);
+	*val = intel_guc_log_level_get(&dev_priv->guc.log);
 
 	return 0;
 }
 
-static int i915_guc_log_control_set(void *data, u64 val)
+static int i915_guc_log_level_set(void *data, u64 val)
 {
 	struct drm_i915_private *dev_priv = data;
 
 	if (!USES_GUC(dev_priv))
 		return -ENODEV;
 
-	return intel_guc_log_control_set(&dev_priv->guc.log, val);
+	return intel_guc_log_level_set(&dev_priv->guc.log, val);
 }
 
-DEFINE_SIMPLE_ATTRIBUTE(i915_guc_log_control_fops,
-			i915_guc_log_control_get, i915_guc_log_control_set,
+DEFINE_SIMPLE_ATTRIBUTE(i915_guc_log_level_fops,
+			i915_guc_log_level_get, i915_guc_log_level_set,
 			"%lld\n");
 
+static int i915_guc_log_relay_open(struct inode *inode, struct file *file)
+{
+	struct drm_i915_private *dev_priv = inode->i_private;
+
+	if (!USES_GUC(dev_priv))
+		return -ENODEV;
+
+	file->private_data = &dev_priv->guc.log;
+
+	return intel_guc_log_relay_open(&dev_priv->guc.log);
+}
+
+static ssize_t
+i915_guc_log_relay_write(struct file *filp,
+			 const char __user *ubuf,
+			 size_t cnt,
+			 loff_t *ppos)
+{
+	struct intel_guc_log *log = filp->private_data;
+
+	intel_guc_log_relay_flush(log);
+
+	return cnt;
+}
+
+static int i915_guc_log_relay_release(struct inode *inode, struct file *file)
+{
+	struct drm_i915_private *dev_priv = inode->i_private;
+
+	intel_guc_log_relay_close(&dev_priv->guc.log);
+
+	return 0;
+}
+
+static const struct file_operations i915_guc_log_relay_fops = {
+	.owner = THIS_MODULE,
+	.open = i915_guc_log_relay_open,
+	.write = i915_guc_log_relay_write,
+	.release = i915_guc_log_relay_release,
+};
+
 static const char *psr2_live_status(u32 val)
 {
 	static const char * const live_status[] = {
@@ -4748,7 +4789,8 @@ static const struct i915_debugfs_files {
 	{"i915_dp_test_data", &i915_displayport_test_data_fops},
 	{"i915_dp_test_type", &i915_displayport_test_type_fops},
 	{"i915_dp_test_active", &i915_displayport_test_active_fops},
-	{"i915_guc_log_control", &i915_guc_log_control_fops},
+	{"i915_guc_log_level", &i915_guc_log_level_fops},
+	{"i915_guc_log_relay", &i915_guc_log_relay_fops},
 	{"i915_hpd_storm_ctl", &i915_hpd_storm_ctl_fops},
 	{"i915_ipc_status", &i915_ipc_status_fops},
 	{"i915_drrs_ctl", &i915_drrs_ctl_fops}