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>

4 files changed, 15 insertions, 16 deletions

diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c
index 7ff1986e5e52..25a0d8e1be51 100644
--- a/drivers/usb/musb/musb_core.c
+++ b/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);
diff --git a/drivers/usb/musb/musb_core.h b/drivers/usb/musb/musb_core.h
index 60b92cbdc7f7..0cef3ceb52c3 100644
--- a/drivers/usb/musb/musb_core.h
+++ b/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)
 
diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index bb684f0f790d..28b9790e84ea 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/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);
 }
 
diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
index 3df6a76b851d..e9f0fd9ddd2d 100644
--- a/drivers/usb/musb/musb_host.c
+++ b/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 */