usb: dwc3: Implement interrupt moderation

Implement interrupt moderation which allows the interrupt rate to be
throttled. To enable this feature the dwc->imod_interval must be set to
1 or greater. This value specifies the minimum inter-interrupt interval,
in 250 ns increments. A value of 0 disables interrupt moderation.

This applies for DWC_usb3 version 3.00a and higher and for DWC_usb31
version 1.20a and higher.

Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Change-Id: I5c5997c6eea817e49102b8e080f3a9bcf45305b4
Git-commit: cf40b86b6ef6df5262ef5a8463b42524e6aa5590
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
[hemantk@codeaurora.org: removed write to DWC3_DEV_IMOD in dwc3_interrupt,
and fixed merge conflicts]
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
Signed-off-by: Mayank Rana <mrana@codeaurora.org>
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index ccdd450..55fbe29 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2099,6 +2099,18 @@
 	u32			reg;
 
 	dbg_event(0xFF, "__Gadgetstart", 0);
+
+	/*
+	 * Use IMOD if enabled via dwc->imod_interval. Otherwise, if
+	 * the core supports IMOD, disable it.
+	 */
+	if (dwc->imod_interval) {
+		dwc3_writel(dwc->regs, DWC3_DEV_IMOD(0), dwc->imod_interval);
+		dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), DWC3_GEVNTCOUNT_EHB);
+	} else if (dwc3_has_imod(dwc)) {
+		dwc3_writel(dwc->regs, DWC3_DEV_IMOD(0), 0);
+	}
+
 	reg = dwc3_readl(dwc->regs, DWC3_DCFG);
 	reg &= ~(DWC3_DCFG_SPEED_MASK);
 
@@ -3485,6 +3497,10 @@
 	reg &= ~DWC3_GEVNTSIZ_INTMASK;
 	dwc3_writel(dwc->regs, DWC3_GEVNTSIZ(0), reg);
 
+	if (dwc->imod_interval)
+		dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0),
+				DWC3_GEVNTCOUNT_EHB);
+
 	return ret;
 }