usb: dwc2: host: Clear interrupts before handling them

In general it is wise to clear interrupts before processing them.  If
you don't do that, you can get:
 1. Interrupt happens
 2. You look at system state and process interrupt
 3. A new interrupt happens
 4. You clear interrupt without processing it.

This patch was actually a first attempt to fix missing device insertions
as described in (usb: dwc2: host: Fix missing device insertions) and it
did solve some of the signal bouncing problems but not all of
them (which is why I submitted the other patch).  Specifically, this
patch itself would sometimes change:
 1. hardware sees connect
 2. hardware sees disconnect
 3. hardware sees connect
 4. dwc2_port_intr() - clears connect interrupt
 5. dwc2_handle_common_intr() - calls dwc2_hcd_disconnect()

...to:
 1. hardware sees connect
 2. hardware sees disconnect
 3. dwc2_port_intr() - clears connect interrupt
 4. hardware sees connect
 5. dwc2_handle_common_intr() - calls dwc2_hcd_disconnect()

...but with different timing then sometimes we'd still miss cable
insertions.

In any case, though this patch doesn't fix any (known) problems, it
still seems wise as a general policy to clear interrupt before handling
them.

Note that for dwc2_handle_usb_port_intr(), instead of moving the clear
of PRTINT to the beginning of the function we remove it completely.  The
only way to clear PRTINT is to clear the sources that set it in the
first place.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>

1 files changed, 9 insertions, 9 deletions

diff --git a/drivers/usb/dwc2/hcd_intr.c b/drivers/usb/dwc2/hcd_intr.c
index a1eb48e54858..f8253803a050 100644
--- a/drivers/usb/dwc2/hcd_intr.c
+++ b/drivers/usb/dwc2/hcd_intr.c
@@ -122,6 +122,9 @@ static void dwc2_sof_intr(struct dwc2_hsotg *hsotg)
 	struct dwc2_qh *qh;
 	enum dwc2_transaction_type tr_type;
 
+	/* Clear interrupt */
+	dwc2_writel(GINTSTS_SOF, hsotg->regs + GINTSTS);
+
 #ifdef DEBUG_SOF
 	dev_vdbg(hsotg->dev, "--Start of Frame Interrupt--\n");
 #endif
@@ -146,9 +149,6 @@ static void dwc2_sof_intr(struct dwc2_hsotg *hsotg)
 	tr_type = dwc2_hcd_select_transactions(hsotg);
 	if (tr_type != DWC2_TRANSACTION_NONE)
 		dwc2_hcd_queue_transactions(hsotg, tr_type);
-
-	/* Clear interrupt */
-	dwc2_writel(GINTSTS_SOF, hsotg->regs + GINTSTS);
 }
 
 /*
@@ -312,6 +312,7 @@ static void dwc2_hprt0_enable(struct dwc2_hsotg *hsotg, u32 hprt0,
 
 	if (do_reset) {
 		*hprt0_modify |= HPRT0_RST;
+		dwc2_writel(*hprt0_modify, hsotg->regs + HPRT0);
 		queue_delayed_work(hsotg->wq_otg, &hsotg->reset_work,
 				   msecs_to_jiffies(60));
 	} else {
@@ -347,11 +348,12 @@ static void dwc2_port_intr(struct dwc2_hsotg *hsotg)
 	 * Set flag and clear if detected
 	 */
 	if (hprt0 & HPRT0_CONNDET) {
+		dwc2_writel(hprt0_modify | HPRT0_CONNDET, hsotg->regs + HPRT0);
+
 		dev_vdbg(hsotg->dev,
 			 "--Port Interrupt HPRT0=0x%08x Port Connect Detected--\n",
 			 hprt0);
 		dwc2_hcd_connect(hsotg);
-		hprt0_modify |= HPRT0_CONNDET;
 
 		/*
 		 * The Hub driver asserts a reset when it sees port connect
@@ -364,10 +366,10 @@ static void dwc2_port_intr(struct dwc2_hsotg *hsotg)
 	 * Clear if detected - Set internal flag if disabled
 	 */
 	if (hprt0 & HPRT0_ENACHG) {
+		dwc2_writel(hprt0_modify | HPRT0_ENACHG, hsotg->regs + HPRT0);
 		dev_vdbg(hsotg->dev,
 			 "  --Port Interrupt HPRT0=0x%08x Port Enable Changed (now %d)--\n",
 			 hprt0, !!(hprt0 & HPRT0_ENA));
-		hprt0_modify |= HPRT0_ENACHG;
 		if (hprt0 & HPRT0_ENA) {
 			hsotg->new_connection = true;
 			dwc2_hprt0_enable(hsotg, hprt0, &hprt0_modify);
@@ -387,15 +389,13 @@ static void dwc2_port_intr(struct dwc2_hsotg *hsotg)
 
 	/* Overcurrent Change Interrupt */
 	if (hprt0 & HPRT0_OVRCURRCHG) {
+		dwc2_writel(hprt0_modify | HPRT0_OVRCURRCHG,
+			    hsotg->regs + HPRT0);
 		dev_vdbg(hsotg->dev,
 			 "  --Port Interrupt HPRT0=0x%08x Port Overcurrent Changed--\n",
 			 hprt0);
 		hsotg->flags.b.port_over_current_change = 1;
-		hprt0_modify |= HPRT0_OVRCURRCHG;
 	}
-
-	/* Clear Port Interrupts */
-	dwc2_writel(hprt0_modify, hsotg->regs + HPRT0);
 }
 
 /*