usb: gadget: u_serial: Implement remote wakeup capability

Implement the remote wakeup capability for u_serial. The newly added
function gserial_wakeup_host() wakes up the host when there is some
data to be sent while the device is suspended. Add gser_get_status()
callbacks to advertise f_serial interface as function wakeup capable.

Signed-off-by: Prashanth K <prashanth.k@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250424121142.4180241-1-prashanth.k@oss.qualcomm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/f_serial.c b/drivers/usb/gadget/function/f_serial.c
index 8f7e7a2b2ff24dd604aba0811c5fdcd830d0f9b2..0f266bc067f5092c0e0cb03fd9aaede1a8225c68 100644 (file)
--- a/drivers/usb/gadget/function/f_serial.c
+++ b/drivers/usb/gadget/function/f_serial.c
@@ -364,6 +364,12 @@ static void gser_suspend(struct usb_function *f)
        gserial_suspend(&gser->port);
 }
 
+static int gser_get_status(struct usb_function *f)
+{
+       return (f->func_wakeup_armed ? USB_INTRF_STAT_FUNC_RW : 0) |
+               USB_INTRF_STAT_FUNC_RW_CAP;
+}
+
 static struct usb_function *gser_alloc(struct usb_function_instance *fi)
 {
        struct f_gser   *gser;
@@ -387,6 +393,7 @@ static struct usb_function *gser_alloc(struct usb_function_instance *fi)
        gser->port.func.free_func = gser_free;
        gser->port.func.resume = gser_resume;
        gser->port.func.suspend = gser_suspend;
+       gser->port.func.get_status = gser_get_status;
 
        return &gser->port.func;
 }

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index 36fff45e8c9b7a5ddfa343d848bcedfeec957549..41dee7c8cc7c3aaa49076a00300d76d7b0cfbc1f 100644 (file)
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -592,6 +592,17 @@ static int gs_start_io(struct gs_port *port)
        return status;
 }
 
+static int gserial_wakeup_host(struct gserial *gser)
+{
+       struct usb_function     *func = &gser->func;
+       struct usb_gadget       *gadget = func->config->cdev->gadget;
+
+       if (func->func_suspended)
+               return usb_func_wakeup(func);
+       else
+               return usb_gadget_wakeup(gadget);
+}
+
 /*-------------------------------------------------------------------------*/
 
 /* TTY Driver */
@@ -746,6 +757,8 @@ static ssize_t gs_write(struct tty_struct *tty, const u8 *buf, size_t count)
 {
        struct gs_port  *port = tty->driver_data;
        unsigned long   flags;
+       int ret = 0;
+       struct gserial  *gser = port->port_usb;
 
        pr_vdebug("gs_write: ttyGS%d (%p) writing %zu bytes\n",
                        port->port_num, tty, count);
@@ -753,6 +766,17 @@ static ssize_t gs_write(struct tty_struct *tty, const u8 *buf, size_t count)
        spin_lock_irqsave(&port->port_lock, flags);
        if (count)
                count = kfifo_in(&port->port_write_buf, buf, count);
+
+       if (port->suspended) {
+               spin_unlock_irqrestore(&port->port_lock, flags);
+               ret = gserial_wakeup_host(gser);
+               if (ret) {
+                       pr_debug("ttyGS%d: Remote wakeup failed:%d\n", port->port_num, ret);
+                       return count;
+               }
+               spin_lock_irqsave(&port->port_lock, flags);
+       }
+
        /* treat count == 0 as flush_chars() */
        if (port->port_usb)
                gs_start_tx(port);
@@ -781,10 +805,22 @@ static void gs_flush_chars(struct tty_struct *tty)
 {
        struct gs_port  *port = tty->driver_data;
        unsigned long   flags;
+       int ret = 0;
+       struct gserial  *gser = port->port_usb;
 
        pr_vdebug("gs_flush_chars: (%d,%p)\n", port->port_num, tty);
 
        spin_lock_irqsave(&port->port_lock, flags);
+       if (port->suspended) {
+               spin_unlock_irqrestore(&port->port_lock, flags);
+               ret = gserial_wakeup_host(gser);
+               if (ret) {
+                       pr_debug("ttyGS%d: Remote wakeup failed:%d\n", port->port_num, ret);
+                       return;
+               }
+               spin_lock_irqsave(&port->port_lock, flags);
+       }
+
        if (port->port_usb)
                gs_start_tx(port);
        spin_unlock_irqrestore(&port->port_lock, flags);
@@ -1464,6 +1500,13 @@ void gserial_suspend(struct gserial *gser)
                return;
        }
 
+       if (port->write_busy || port->write_started) {
+               /* Wakeup to host if there are ongoing transfers */
+               spin_unlock_irqrestore(&serial_port_lock, flags);
+               if (!gserial_wakeup_host(gser))
+                       return;
+       }
+
        spin_lock(&port->port_lock);
        spin_unlock(&serial_port_lock);
        port->suspended = true;