linux-kernel - [PATCH v1 2/2] usb: gadget: dummy_hcd: Set transfer interval to 1 microframe

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Message-ID: <6295dbb84ca76884551df9eb157cce569377a22c.1712843963.git.sylv@sylv.io>
Date: Thu, 11 Apr 2024 17:22:11 +0200
From: Marcello Sylvester Bauer <sylv@...v.io>
To: linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Marcello Sylvester Bauer <marcello.bauer@...ements.com>,
	Matthias Stoeckl <matthias.stoeckl@...unet.com>,
	Uwe Kleine-Koenig <u.kleine-koenig@...gutronix.de>,
	Marcello Sylvester Bauer <sylv@...v.io>
Subject: [PATCH v1 2/2] usb: gadget: dummy_hcd: Set transfer interval to 1 microframe

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@...ements.com>
Signed-off-by: Marcello Sylvester Bauer <sylv@...v.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 */
+
 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);
-- 
2.44.0