linux-kernel - [PATCH 3.2 005/164] usb: musb: core: fix TX/RX endpoint order

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Message-ID: <lsq.1438473757.717873468@decadent.org.uk>
Date:	Sun, 02 Aug 2015 01:02:37 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Felipe Balbi" <balbi@...com>
Subject: [PATCH 3.2 005/164] usb: musb: core: fix TX/RX endpoint order

3.2.70-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Felipe Balbi <balbi@...com>

commit e3c93e1a3f35be4cf1493d3ccfb0c6d9209e4922 upstream.

As per Mentor Graphics' documentation, we should
always handle TX endpoints before RX endpoints.

This patch fixes that error while also updating
some hard-to-read comments which were scattered
around musb_interrupt().

This patch should be backported as far back as
possible since this error has been in the driver
since it's conception.

Signed-off-by: Felipe Balbi <balbi@...com>
[bwh: Backported to 3.2: adjust context, indentation]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/musb/musb_core.c | 44 ++++++++++++++++++++++++++------------------
 1 file changed, 26 insertions(+), 18 deletions(-)

--- a/drivers/usb/musb/musb_core.c
+++ b/drivers/usb/musb/musb_core.c
@@ -1524,16 +1524,30 @@ irqreturn_t musb_interrupt(struct musb *
 		(devctl & MUSB_DEVCTL_HM) ? "host" : "peripheral",
 		musb->int_usb, musb->int_tx, musb->int_rx);
 
-	/* the core can interrupt us for multiple reasons; docs have
-	 * a generic interrupt flowchart to follow
+	/**
+	 * According to Mentor Graphics' documentation, flowchart on page 98,
+	 * IRQ should be handled as follows:
+	 *
+	 * . Resume IRQ
+	 * . Session Request IRQ
+	 * . VBUS Error IRQ
+	 * . Suspend IRQ
+	 * . Connect IRQ
+	 * . Disconnect IRQ
+	 * . Reset/Babble IRQ
+	 * . SOF IRQ (we're not using this one)
+	 * . Endpoint 0 IRQ
+	 * . TX Endpoints
+	 * . RX Endpoints
+	 *
+	 * We will be following that flowchart in order to avoid any problems
+	 * that might arise with internal Finite State Machine.
 	 */
+
 	if (musb->int_usb)
 		retval |= musb_stage0_irq(musb, musb->int_usb,
 				devctl, power);
 
-	/* "stage 1" is handling endpoint irqs */
-
-	/* handle endpoint 0 first */
 	if (musb->int_tx & 1) {
 		if (devctl & MUSB_DEVCTL_HM)
 			retval |= musb_h_ep0_irq(musb);
@@ -1541,43 +1555,37 @@ irqreturn_t musb_interrupt(struct musb *
 			retval |= musb_g_ep0_irq(musb);
 	}
 
-	/* RX on endpoints 1-15 */
-	reg = musb->int_rx >> 1;
+	reg = musb->int_tx >> 1;
 	ep_num = 1;
 	while (reg) {
 		if (reg & 1) {
-			/* musb_ep_select(musb->mregs, ep_num); */
-			/* REVISIT just retval = ep->rx_irq(...) */
 			retval = IRQ_HANDLED;
 			if (devctl & MUSB_DEVCTL_HM) {
 				if (is_host_capable())
-					musb_host_rx(musb, ep_num);
+					musb_host_tx(musb, ep_num);
 			} else {
 				if (is_peripheral_capable())
-					musb_g_rx(musb, ep_num);
+					musb_g_tx(musb, ep_num);
 			}
 		}
-
 		reg >>= 1;
 		ep_num++;
 	}
 
-	/* TX on endpoints 1-15 */
-	reg = musb->int_tx >> 1;
+	reg = musb->int_rx >> 1;
 	ep_num = 1;
 	while (reg) {
 		if (reg & 1) {
-			/* musb_ep_select(musb->mregs, ep_num); */
-			/* REVISIT just retval |= ep->tx_irq(...) */
 			retval = IRQ_HANDLED;
 			if (devctl & MUSB_DEVCTL_HM) {
 				if (is_host_capable())
-					musb_host_tx(musb, ep_num);
+					musb_host_rx(musb, ep_num);
 			} else {
 				if (is_peripheral_capable())
-					musb_g_tx(musb, ep_num);
+					musb_g_rx(musb, ep_num);
 			}
 		}
+
 		reg >>= 1;
 		ep_num++;
 	}

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