usb: musb: Perform only write access on MUSB_INTRTXE

This is part of the workaround for AM35x advisory Advisory 1.1.20.
The advisory says that the IPSS bridge can't handle 8 & 16 bit read
access. An 16bit read access to MUSB_INTRTXE results in an 32bit read
access which also reads INTRRX and therefore may lose interrupts.
This patch uses a shadow register of MUSB_INTRTXE so we only perform
write access to it.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_core.c

@@ -724,7 +724,8 @@ static irqreturn_t musb_stage0_irq(struct musb *musb, u8 int_usb,
 		if (is_peripheral_active(musb)) {
 			/* REVISIT HNP; just force disconnect */
 		}
-		musb_writew(musb->mregs, MUSB_INTRTXE, musb->epmask);
+		musb->intrtxe = musb->epmask;
+		musb_writew(musb->mregs, MUSB_INTRTXE, musb->intrtxe);
 		musb->intrrxe = musb->epmask & 0xfffe;
 		musb_writew(musb->mregs, MUSB_INTRRXE, musb->intrrxe);
 		musb_writeb(musb->mregs, MUSB_INTRUSBE, 0xf7);
@@ -947,7 +948,8 @@ void musb_start(struct musb *musb)
 	dev_dbg(musb->controller, "<== devctl %02x\n", devctl);
 
 	/*  Set INT enable registers, enable interrupts */
-	musb_writew(regs, MUSB_INTRTXE, musb->epmask);
+	musb->intrtxe = musb->epmask;
+	musb_writew(regs, MUSB_INTRTXE, musb->intrtxe);
 	musb->intrrxe = musb->epmask & 0xfffe;
 	musb_writew(regs, MUSB_INTRRXE, musb->intrrxe);
 	musb_writeb(regs, MUSB_INTRUSBE, 0xf7);
@@ -987,6 +989,7 @@ static void musb_generic_disable(struct musb *musb)
 
 	/* disable interrupts */
 	musb_writeb(mbase, MUSB_INTRUSBE, 0);
+	musb->intrtxe = 0;
 	musb_writew(mbase, MUSB_INTRTXE, 0);
 	musb->intrrxe = 0;
 	musb_writew(mbase, MUSB_INTRRXE, 0);
@@ -2124,7 +2127,6 @@ static void musb_save_context(struct musb *musb)
 	musb->context.testmode = musb_readb(musb_base, MUSB_TESTMODE);
 	musb->context.busctl = musb_read_ulpi_buscontrol(musb->mregs);
 	musb->context.power = musb_readb(musb_base, MUSB_POWER);
-	musb->context.intrtxe = musb_readw(musb_base, MUSB_INTRTXE);
 	musb->context.intrusbe = musb_readb(musb_base, MUSB_INTRUSBE);
 	musb->context.index = musb_readb(musb_base, MUSB_INDEX);
 	musb->context.devctl = musb_readb(musb_base, MUSB_DEVCTL);
@@ -2197,7 +2199,7 @@ static void musb_restore_context(struct musb *musb)
 	musb_writeb(musb_base, MUSB_TESTMODE, musb->context.testmode);
 	musb_write_ulpi_buscontrol(musb->mregs, musb->context.busctl);
 	musb_writeb(musb_base, MUSB_POWER, musb->context.power);
-	musb_writew(musb_base, MUSB_INTRTXE, musb->context.intrtxe);
+	musb_writew(musb_base, MUSB_INTRTXE, musb->intrtxe);
 	musb_writew(musb_base, MUSB_INTRRXE, musb->intrrxe);
 	musb_writeb(musb_base, MUSB_INTRUSBE, musb->context.intrusbe);
 	musb_writeb(musb_base, MUSB_DEVCTL, musb->context.devctl);

drivers/usb/musb/musb_core.h

@@ -288,7 +288,6 @@ struct musb_csr_regs {
 struct musb_context_registers {
 
 	u8 power;
-	u16 intrtxe;
 	u8 intrusbe;
 	u16 frame;
 	u8 index, testmode;
@@ -314,6 +313,7 @@ struct musb {
 	u16			hwvers;
 
 	u16			intrrxe;
+	u16			intrtxe;
 /* this hub status bit is reserved by USB 2.0 and not seen by usbcore */
 #define MUSB_PORT_STAT_RESUME	(1 << 31)
 

drivers/usb/musb/musb_gadget.c

@@ -1068,7 +1068,6 @@ static int musb_gadget_enable(struct usb_ep *ep,
 	 */
 	musb_ep_select(mbase, epnum);
 	if (usb_endpoint_dir_in(desc)) {
-		u16 int_txe = musb_readw(mbase, MUSB_INTRTXE);
 
 		if (hw_ep->is_shared_fifo)
 			musb_ep->is_in = 1;
@@ -1080,8 +1079,8 @@ static int musb_gadget_enable(struct usb_ep *ep,
 			goto fail;
 		}
 
-		int_txe |= (1 << epnum);
-		musb_writew(mbase, MUSB_INTRTXE, int_txe);
+		musb->intrtxe |= (1 << epnum);
+		musb_writew(mbase, MUSB_INTRTXE, musb->intrtxe);
 
 		/* REVISIT if can_bulk_split(), use by updating "tmp";
 		 * likewise high bandwidth periodic tx
@@ -1208,9 +1207,8 @@ static int musb_gadget_disable(struct usb_ep *ep)
 
 	/* zero the endpoint sizes */
 	if (musb_ep->is_in) {
-		u16 int_txe = musb_readw(musb->mregs, MUSB_INTRTXE);
-		int_txe &= ~(1 << epnum);
-		musb_writew(musb->mregs, MUSB_INTRTXE, int_txe);
+		musb->intrtxe &= ~(1 << epnum);
+		musb_writew(musb->mregs, MUSB_INTRTXE, musb->intrtxe);
 		musb_writew(epio, MUSB_TXMAXP, 0);
 	} else {
 		musb->intrrxe &= ~(1 << epnum);
@@ -1530,7 +1528,7 @@ static void musb_gadget_fifo_flush(struct usb_ep *ep)
 	void __iomem	*epio = musb->endpoints[epnum].regs;
 	void __iomem	*mbase;
 	unsigned long	flags;
-	u16		csr, int_txe;
+	u16		csr;
 
 	mbase = musb->mregs;
 
@@ -1538,8 +1536,7 @@ static void musb_gadget_fifo_flush(struct usb_ep *ep)
 	musb_ep_select(mbase, (u8) epnum);
 
 	/* disable interrupts */
-	int_txe = musb_readw(mbase, MUSB_INTRTXE);
-	musb_writew(mbase, MUSB_INTRTXE, int_txe & ~(1 << epnum));
+	musb_writew(mbase, MUSB_INTRTXE, musb->intrtxe & ~(1 << epnum));
 
 	if (musb_ep->is_in) {
 		csr = musb_readw(epio, MUSB_TXCSR);
@@ -1563,7 +1560,7 @@ static void musb_gadget_fifo_flush(struct usb_ep *ep)
 	}
 
 	/* re-enable interrupt */
-	musb_writew(mbase, MUSB_INTRTXE, int_txe);
+	musb_writew(mbase, MUSB_INTRTXE, musb->intrtxe);
 	spin_unlock_irqrestore(&musb->lock, flags);
 }
 

drivers/usb/musb/musb_host.c

@@ -740,7 +740,7 @@ static void musb_ep_program(struct musb *musb, u8 epnum,
 		csr = musb_readw(epio, MUSB_TXCSR);
 
 		/* disable interrupt in case we flush */
-		int_txe = musb_readw(mbase, MUSB_INTRTXE);
+		int_txe = musb->intrtxe;
 		musb_writew(mbase, MUSB_INTRTXE, int_txe & ~(1 << epnum));
 
 		/* general endpoint setup */