Hi,
On Sun, Jan 13, 2013 at 08:09:14PM +0100, masekp@xxxxxxxxxxxx wrote:
> Hello guys,
> I've found a following problems on BeagleBoard and Kernel 3.0.8 with
> gadget serial driver.
>
> Attached is a small program, which opens gadget serial tty at
> /dev/ttyGS0. USB is NOT connected to host. Then it fills it's output
> fifo up. Before closing, it flushes the output fifo. But despite
> that, call to close function on last line blocks for 15seconds!
>
> To me it looks like fifo flushing doesn't work. If I do this on
> regular serial port on PC and if I remove output fifo flushing, close
> also blocks (as I have flow control set). But if the flushing is
> present, close returns immediately on PC.
>
> On gadget serial, it always block for 15s.
>
> So it looks to me like a bug in gadget serial driver. Or is there any
> other cleanup, which I should do? Or at least some option how to
> lower the timeout value?
>
> thank you and best regards
I haven't even compile tested this, but something like below is probably
what you need:
diff --git a/drivers/usb/gadget/u_serial.c b/drivers/usb/gadget/u_serial.c
index 598dcc1..adba385 100644
--- a/drivers/usb/gadget/u_serial.c
+++ b/drivers/usb/gadget/u_serial.c
@@ -936,8 +936,10 @@ static void gs_flush_chars(struct tty_struct *tty)
pr_vdebug("gs_flush_chars: (%d,%p)\n", port->port_num, tty);
spin_lock_irqsave(&port->port_lock, flags);
- if (port->port_usb)
+ if (port->port_usb) {
+ gs_buf_clear(&port->port_write_buf);
gs_start_tx(port);
+ }
spin_unlock_irqrestore(&port->port_lock, flags);
}
needs proper testing however. If you look at gs_start_tx(), you'll see
that it waits up to 15 seconds for port_write_buf to be cleared. In fact
I think gs_start_tx() shouldn't even be called from gs_flush_chars(),
IIUC, gs_flush_chars() should call usb_ep_dequeue() on every single
pending request and then call gs_buf_clear(), but that'll be a much more
involved work which I'll try to do later this week.
Meanwhile, can you see if patch above breaks anything ?
cheers
--
balbi
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