usb: dwc2: gadget: add device tree property to enable dma

* Add an of specific function to parse device node properties.
* Enable dma usage only if device tree property 'g_use_dma' is present.
Tested-by: NRobert Baldyga <r.baldyga@samsung.com>
Acked-by: NPaul Zimmerman <paulz@synopsys.com>
Signed-off-by: NGregory Herrero <gregory.herrero@intel.com>
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/usb/dwc2/core.h

@@ -563,6 +563,7 @@ struct dwc2_hw_params {
  * @setup:              NAK management for EP0 SETUP
  * @last_rst:           Time of last reset
  * @eps:                The endpoints being supplied to the gadget framework
+ * @g_using_dma:          Indicate if dma usage is enabled
  */
 struct dwc2_hsotg {
 	struct device *dev;
@@ -696,6 +697,7 @@ struct dwc2_hsotg {
 	unsigned int setup:1;
 	unsigned long last_rst;
 	struct s3c_hsotg_ep *eps;
+	u32 g_using_dma;
 #endif /* CONFIG_USB_DWC2_PERIPHERAL || CONFIG_USB_DWC2_DUAL_ROLE */
 };
 

drivers/usb/dwc2/gadget.c

@@ -85,11 +85,11 @@ static void s3c_hsotg_dump(struct dwc2_hsotg *hsotg);
  * a core reset. This means we either need to fix the gadgets to take
  * account of DMA alignment, or add bounce buffers (yuerk).
  *
- * Until this issue is sorted out, we always return 'false'.
+ * g_using_dma is set depending on dts flag.
  */
 static inline bool using_dma(struct dwc2_hsotg *hsotg)
 {
-	return false;	/* support is not complete */
+	return hsotg->g_using_dma;
 }
 
 /**
@@ -3402,6 +3402,18 @@ static void s3c_hsotg_delete_debug(struct dwc2_hsotg *hsotg)
 	debugfs_remove(hsotg->debug_root);
 }
 
+#ifdef CONFIG_OF
+static void s3c_hsotg_of_probe(struct dwc2_hsotg *hsotg)
+{
+	struct device_node *np = hsotg->dev->of_node;
+
+	/* Enable dma if requested in device tree */
+	hsotg->g_using_dma = of_property_read_bool(np, "g-use-dma");
+}
+#else
+static inline void s3c_hsotg_of_probe(struct dwc2_hsotg *hsotg) { }
+#endif
+
 /**
  * dwc2_gadget_init - init function for gadget
  * @dwc2: The data structure for the DWC2 driver.
@@ -3419,6 +3431,8 @@ int dwc2_gadget_init(struct dwc2_hsotg *hsotg, int irq)
 	/* Set default UTMI width */
 	hsotg->phyif = GUSBCFG_PHYIF16;
 
+	s3c_hsotg_of_probe(hsotg);
+
 	/*
 	 * If platform probe couldn't find a generic PHY or an old style
 	 * USB PHY, fall back to pdata