usb: musb: Perform only write access on MUSB_INTRRXE

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_INTRRXE results in an 32bit read
access which also reads INTRUSB and therefore may lose interrupts.
This patch uses a shadow register of MUSB_INTRRXE 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>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c
index d156fe8bebfa..7ff1986e5e52 100644
--- a/drivers/usb/musb/musb_core.c
+++ b/drivers/usb/musb/musb_core.c
@@ -725,7 +725,8 @@ static irqreturn_t musb_stage0_irq(struct musb *musb, u8 int_usb,
                         /* REVISIT HNP; just force disconnect */
                 }
                 musb_writew(musb->mregs, MUSB_INTRTXE, musb->epmask);
-                musb_writew(musb->mregs, MUSB_INTRRXE, musb->epmask & 0xfffe);
+                musb->intrrxe = musb->epmask & 0xfffe;
+                musb_writew(musb->mregs, MUSB_INTRRXE, musb->intrrxe);
                 musb_writeb(musb->mregs, MUSB_INTRUSBE, 0xf7);
                 musb->port1_status &= ~(USB_PORT_STAT_LOW_SPEED
                                         |USB_PORT_STAT_HIGH_SPEED
@@ -947,7 +948,8 @@ void musb_start(struct musb *musb)
 
         /*  Set INT enable registers, enable interrupts */
         musb_writew(regs, MUSB_INTRTXE, musb->epmask);
-        musb_writew(regs, MUSB_INTRRXE, musb->epmask & 0xfffe);
+        musb->intrrxe = musb->epmask & 0xfffe;
+        musb_writew(regs, MUSB_INTRRXE, musb->intrrxe);
         musb_writeb(regs, MUSB_INTRUSBE, 0xf7);
 
         musb_writeb(regs, MUSB_TESTMODE, 0);
@@ -986,6 +988,7 @@ static void musb_generic_disable(struct musb *musb)
         /* disable interrupts */
         musb_writeb(mbase, MUSB_INTRUSBE, 0);
         musb_writew(mbase, MUSB_INTRTXE, 0);
+        musb->intrrxe = 0;
         musb_writew(mbase, MUSB_INTRRXE, 0);
 
         /* off */
@@ -2122,7 +2125,6 @@ static void musb_save_context(struct musb *musb)
         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.intrrxe = musb_readw(musb_base, MUSB_INTRRXE);
         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);
@@ -2196,7 +2198,7 @@ static void musb_restore_context(struct musb *musb)
         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_INTRRXE, musb->context.intrrxe);
+        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);