brcmfmac: add "reset" debugfs entry for testing reset

This is a trivial debugfs entry for triggering reset just like in case
of firmware crash. It works by writing 1 to it:
echo 1 > reset
Signed-off-by: NRafał Miłecki <rafal@milecki.pl>
Signed-off-by: NKalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c

@@ -1086,6 +1086,29 @@ static void brcmf_core_bus_reset(struct work_struct *work)
 	brcmf_bus_reset(drvr->bus_if);
 }
 
+static ssize_t bus_reset_write(struct file *file, const char __user *user_buf,
+			       size_t count, loff_t *ppos)
+{
+	struct brcmf_pub *drvr = file->private_data;
+	u8 value;
+
+	if (kstrtou8_from_user(user_buf, count, 0, &value))
+		return -EINVAL;
+
+	if (value != 1)
+		return -EINVAL;
+
+	schedule_work(&drvr->bus_reset);
+
+	return count;
+}
+
+static const struct file_operations bus_reset_fops = {
+	.open	= simple_open,
+	.llseek	= no_llseek,
+	.write	= bus_reset_write,
+};
+
 static int brcmf_bus_started(struct brcmf_pub *drvr, struct cfg80211_ops *ops)
 {
 	int ret = -1;
@@ -1161,6 +1184,8 @@ static int brcmf_bus_started(struct brcmf_pub *drvr, struct cfg80211_ops *ops)
 
 	/* populate debugfs */
 	brcmf_debugfs_add_entry(drvr, "revinfo", brcmf_revinfo_read);
+	debugfs_create_file("reset", 0600, brcmf_debugfs_get_devdir(drvr), drvr,
+			    &bus_reset_fops);
 	brcmf_feat_debugfs_create(drvr);
 	brcmf_proto_debugfs_create(drvr);
 	brcmf_bus_debugfs_create(bus_if);