[PATCH v2 2/2] USB: usb resume time delay debug

[Todd Brandt]

add debugfs support for experimenting with USB timing delay
values on the fly. Values are read/written from debugfs at
/sys/kernel/debug/usb/timing.

Signed-off-by: Todd Brandt <todd.e.bra...@linux.intel.com>
---
v2 changes:
 - moved the debug code from hub.c to usb.c
 - use debugfs instead of /sys/kernel/usb

 drivers/usb/core/usb.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index 7859e8a..f81f66b 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -39,6 +39,8 @@
 #include <linux/mutex.h>
 #include <linux/workqueue.h>
 #include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/uaccess.h>
 #include <linux/usb/of.h>
 
 #include <asm/io.h>
@@ -1042,6 +1044,49 @@ struct dentry *usb_debug_root;
 EXPORT_SYMBOL_GPL(usb_debug_root);
 
 static struct dentry *usb_debug_devices;
+static struct dentry *usb_debug_timing;
+
+static int usb_timing_show(struct seq_file *s, void *unused)
+{
+       seq_printf(s, "tdrsmdn=%d\n", usb_timing.tdrsmdn);
+       seq_printf(s, "trsmrcy=%d\n", usb_timing.trsmrcy);
+       seq_printf(s, "trstrcy=%d\n", usb_timing.trstrcy);
+       return 0;
+}
+
+static int usb_timing_open(struct inode *inode, struct file *file)
+{
+       return single_open(file, usb_timing_show, inode->i_private);
+}
+
+static ssize_t usb_timing_write(struct file *file,
+               const char __user *ubuf, size_t count, loff_t *ppos)
+{
+       int val;
+       char buf[32];
+
+       if (copy_from_user(&buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
+               return -EFAULT;
+
+       if (sscanf(buf, "tdrsmdn=%u", &val) == 1)
+               usb_timing.tdrsmdn = max(val, USB_TIMING_TDRSMDN_MIN);
+       else if (sscanf(buf, "trsmrcy=%u", &val) == 1)
+               usb_timing.trsmrcy = max(val, USB_TIMING_TRSMRCY_MIN);
+       else if (sscanf(buf, "trstrcy=%u", &val) == 1)
+               usb_timing.trstrcy = max(val, USB_TIMING_TRSTRCY_MIN);
+       else
+               return -EINVAL;
+
+       return count;
+}
+
+static const struct file_operations usbfs_timing_fops = {
+       .open     = usb_timing_open,
+       .write    = usb_timing_write,
+       .read     = seq_read,
+       .llseek   = seq_lseek,
+       .release  = single_release,
+};
 
 static int usb_debugfs_init(void)
 {
@@ -1058,11 +1103,21 @@ static int usb_debugfs_init(void)
                return -ENOENT;
        }
 
+       usb_debug_timing = debugfs_create_file("timing", 0644,
+                                               usb_debug_root, NULL,
+                                               &usbfs_timing_fops);
+       if (!usb_debug_timing) {
+               debugfs_remove(usb_debug_root);
+               usb_debug_root = NULL;
+               return -ENOENT;
+       }
+
        return 0;
 }
 
 static void usb_debugfs_cleanup(void)
 {
+       debugfs_remove(usb_debug_timing);
        debugfs_remove(usb_debug_devices);
        debugfs_remove(usb_debug_root);
 }
-- 
2.1.4

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