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List:       linux-usb
Subject:    [PATCH 19/21] USB: musb: use right poll limit for low speed devices
From:       Greg Kroah-Hartman <gregkh () suse ! de>
Date:       2009-02-27 22:48:40
Message-ID: 1235774922-19662-19-git-send-email-gregkh () suse ! de
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From: Sergei Shtylyov <sshtylyov@ru.mvista.com>

Remove wrongly applied upper limit on the interrupt transfer
interval for low speed devices (not much of an error per se,
according to USB specs).

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
 drivers/usb/musb/musb_host.c |   18 ++++++++++--------
 1 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
index 23d3890..6dbbd07 100644
--- a/drivers/usb/musb/musb_host.c
+++ b/drivers/usb/musb/musb_host.c
@@ -1863,19 +1863,21 @@ static int musb_urb_enqueue(
 	}
 	qh->type_reg = type_reg;
 
-	/* precompute rxinterval/txinterval register */
-	interval = min((u8)16, epd->bInterval);	/* log encoding */
+	/* Precompute RXINTERVAL/TXINTERVAL register */
 	switch (qh->type) {
 	case USB_ENDPOINT_XFER_INT:
-		/* fullspeed uses linear encoding */
-		if (USB_SPEED_FULL == urb->dev->speed) {
-			interval = epd->bInterval;
-			if (!interval)
-				interval = 1;
+		/*
+		 * Full/low speeds use the  linear encoding,
+		 * high speed uses the logarithmic encoding.
+		 */
+		if (urb->dev->speed <= USB_SPEED_FULL) {
+			interval = max_t(u8, epd->bInterval, 1);
+			break;
 		}
 		/* FALLTHROUGH */
 	case USB_ENDPOINT_XFER_ISOC:
-		/* iso always uses log encoding */
+		/* ISO always uses logarithmic encoding */
+		interval = min_t(u8, epd->bInterval, 16);
 		break;
 	default:
 		/* REVISIT we actually want to use NAK limits, hinting to the
-- 
1.6.0.2

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