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.brandt@xxxxxxxxxxxxxxx>
---
v2:
- moved the debug code from hub.c to usb.c
- use debugfs instead of /sys/kernel/usb
v5:
- allow setting tdrstr
drivers/usb/core/usb.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 58 insertions(+)
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index ac31263..bef73c2 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>
@@ -1036,6 +1038,52 @@ 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);
+ seq_printf(s, "tdrstr=%d\n", usb_timing.tdrstr);
+ 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 if (sscanf(buf, "tdrstr=%u", &val) == 1)
+ usb_timing.tdrstr = max(val, USB_TIMING_TDRSTR_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)
{
@@ -1052,11 +1100,21 @@ 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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