diff mbox series

[v1,2/2] usb: gadget: dummy_hcd: Set transfer interval to 1 microframe

Message ID 6295dbb84ca76884551df9eb157cce569377a22c.1712843963.git.sylv@sylv.io (mailing list archive)
State Accepted
Commit 0a723ed3baa941ca4f51d87bab00661f41142835
Headers show
Series usb: gadget: dummy_hcd: Switch to hrtimers for better performance | expand

Commit Message

Marcello Sylvester Bauer April 11, 2024, 2:51 p.m. UTC
From: Marcello Sylvester Bauer <sylv@sylv.io>

Currently, the transfer polling interval is set to 1ms, which is the
frame rate of full-speed and low-speed USB. The USB 2.0 specification
introduces microframes (125 microseconds) to improve the timing
precision of data transfers.

Reducing the transfer interval to 1 microframe increases data throughput
for high-speed and super-speed USB communication

Signed-off-by: Marcello Sylvester Bauer <marcello.bauer@9elements.com>
Signed-off-by: Marcello Sylvester Bauer <sylv@sylv.io>
---
 drivers/usb/gadget/udc/dummy_hcd.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Comments

Alan Stern April 11, 2024, 4:21 p.m. UTC | #1
On Thu, Apr 11, 2024 at 05:22:11PM +0200, Marcello Sylvester Bauer wrote:
> Currently, the transfer polling interval is set to 1ms, which is the
> frame rate of full-speed and low-speed USB. The USB 2.0 specification
> introduces microframes (125 microseconds) to improve the timing
> precision of data transfers.
> 
> Reducing the transfer interval to 1 microframe increases data throughput
> for high-speed and super-speed USB communication
> 
> Signed-off-by: Marcello Sylvester Bauer <marcello.bauer@9elements.com>
> Signed-off-by: Marcello Sylvester Bauer <sylv@sylv.io>
> ---
>  drivers/usb/gadget/udc/dummy_hcd.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/gadget/udc/dummy_hcd.c b/drivers/usb/gadget/udc/dummy_hcd.c
> index dab559d8ee8c..f37b0d8386c1 100644
> --- a/drivers/usb/gadget/udc/dummy_hcd.c
> +++ b/drivers/usb/gadget/udc/dummy_hcd.c
> @@ -50,6 +50,8 @@
>  #define POWER_BUDGET	500	/* in mA; use 8 for low-power port testing */
>  #define POWER_BUDGET_3	900	/* in mA */
>  
> +#define DUMMY_TIMER_INT_NSECS	125000 /* 1 microframe */

If the is_super_speed and is_high_speed module parameters are both false 
then the timer should run at 1-ms intervals.  So this needs to be 
something that can be adjusted at runtime, not a constant.

Alan Stern
diff mbox series

Patch

diff --git a/drivers/usb/gadget/udc/dummy_hcd.c b/drivers/usb/gadget/udc/dummy_hcd.c
index dab559d8ee8c..f37b0d8386c1 100644
--- a/drivers/usb/gadget/udc/dummy_hcd.c
+++ b/drivers/usb/gadget/udc/dummy_hcd.c
@@ -50,6 +50,8 @@ 
 #define POWER_BUDGET	500	/* in mA; use 8 for low-power port testing */
 #define POWER_BUDGET_3	900	/* in mA */
 
+#define DUMMY_TIMER_INT_NSECS	125000 /* 1 microframe */
+
 static const char	driver_name[] = "dummy_hcd";
 static const char	driver_desc[] = "USB Host+Gadget Emulator";
 
@@ -1302,7 +1304,7 @@  static int dummy_urb_enqueue(
 
 	/* kick the scheduler, it'll do the rest */
 	if (!hrtimer_active(&dum_hcd->timer))
-		hrtimer_start(&dum_hcd->timer, ms_to_ktime(1), HRTIMER_MODE_REL);
+		hrtimer_start(&dum_hcd->timer, ns_to_ktime(DUMMY_TIMER_INT_NSECS), HRTIMER_MODE_REL);
 
  done:
 	spin_unlock_irqrestore(&dum_hcd->dum->lock, flags);
@@ -1993,7 +1995,7 @@  static enum hrtimer_restart dummy_timer(struct hrtimer *t)
 		dum_hcd->udev = NULL;
 	} else if (dum_hcd->rh_state == DUMMY_RH_RUNNING) {
 		/* want a 1 msec delay here */
-		hrtimer_start(&dum_hcd->timer, ms_to_ktime(1), HRTIMER_MODE_REL);
+		hrtimer_start(&dum_hcd->timer, ns_to_ktime(DUMMY_TIMER_INT_NSECS), HRTIMER_MODE_REL);
 	}
 
 	spin_unlock_irqrestore(&dum->lock, flags);