usb: dwc2: gadget: Add DMA descriptor chains for EP 0

Update dwc2_hsotg structure to add descriptor chains for EP 0: two DMA
descriptors for Setup phase, per one for IN/OUT data and status phases.
Add their allocation function dwc2_gadget_alloc_ctrl_desc_chains() and
its call during gadget probe.
Signed-off-by: Vahram Aharonyan <vahrama@synopsys.com>
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc2/core.h

@@ -884,6 +884,12 @@ struct dwc2_hregs_backup {
  * @ctrl_req:           Request for EP0 control packets.
  * @ep0_state:          EP0 control transfers state
  * @test_mode:          USB test mode requested by the host
+ * @setup_desc_dma:	EP0 setup stage desc chain DMA address
+ * @setup_desc:		EP0 setup stage desc chain pointer
+ * @ctrl_in_desc_dma:	EP0 IN data phase desc chain DMA address
+ * @ctrl_in_desc:	EP0 IN data phase desc chain pointer
+ * @ctrl_out_desc_dma:	EP0 OUT data phase desc chain DMA address
+ * @ctrl_out_desc:	EP0 OUT data phase desc chain pointer
  * @eps:                The endpoints being supplied to the gadget framework
  */
 struct dwc2_hsotg {
@@ -1027,6 +1033,13 @@ struct dwc2_hsotg {
 	enum dwc2_ep0_state ep0_state;
 	u8 test_mode;
 
+	dma_addr_t setup_desc_dma[2];
+	struct dwc2_dma_desc *setup_desc[2];
+	dma_addr_t ctrl_in_desc_dma;
+	struct dwc2_dma_desc *ctrl_in_desc;
+	dma_addr_t ctrl_out_desc_dma;
+	struct dwc2_dma_desc *ctrl_out_desc;
+
 	struct usb_gadget gadget;
 	unsigned int enabled:1;
 	unsigned int connected:1;

drivers/usb/dwc2/gadget.c

@@ -324,6 +324,54 @@ static void dwc2_hsotg_unmap_dma(struct dwc2_hsotg *hsotg,
 	usb_gadget_unmap_request(&hsotg->gadget, req, hs_ep->dir_in);
 }
 
+/*
+ * dwc2_gadget_alloc_ctrl_desc_chains - allocate DMA descriptor chains
+ * for Control endpoint
+ * @hsotg: The device state.
+ *
+ * This function will allocate 4 descriptor chains for EP 0: 2 for
+ * Setup stage, per one for IN and OUT data/status transactions.
+ */
+static int dwc2_gadget_alloc_ctrl_desc_chains(struct dwc2_hsotg *hsotg)
+{
+	hsotg->setup_desc[0] =
+		dmam_alloc_coherent(hsotg->dev,
+				    sizeof(struct dwc2_dma_desc),
+				    &hsotg->setup_desc_dma[0],
+				    GFP_KERNEL);
+	if (!hsotg->setup_desc[0])
+		goto fail;
+
+	hsotg->setup_desc[1] =
+		dmam_alloc_coherent(hsotg->dev,
+				    sizeof(struct dwc2_dma_desc),
+				    &hsotg->setup_desc_dma[1],
+				    GFP_KERNEL);
+	if (!hsotg->setup_desc[1])
+		goto fail;
+
+	hsotg->ctrl_in_desc =
+		dmam_alloc_coherent(hsotg->dev,
+				    sizeof(struct dwc2_dma_desc),
+				    &hsotg->ctrl_in_desc_dma,
+				    GFP_KERNEL);
+	if (!hsotg->ctrl_in_desc)
+		goto fail;
+
+	hsotg->ctrl_out_desc =
+		dmam_alloc_coherent(hsotg->dev,
+				    sizeof(struct dwc2_dma_desc),
+				    &hsotg->ctrl_out_desc_dma,
+				    GFP_KERNEL);
+	if (!hsotg->ctrl_out_desc)
+		goto fail;
+
+	return 0;
+
+fail:
+	return -ENOMEM;
+}
+
 /**
  * dwc2_hsotg_write_fifo - write packet Data to the TxFIFO
  * @hsotg: The controller state.
@@ -3857,6 +3905,12 @@ int dwc2_gadget_init(struct dwc2_hsotg *hsotg, int irq)
 	if (!hsotg->ep0_buff)
 		return -ENOMEM;
 
+	if (using_desc_dma(hsotg)) {
+		ret = dwc2_gadget_alloc_ctrl_desc_chains(hsotg);
+		if (ret < 0)
+			return ret;
+	}
+
 	ret = devm_request_irq(hsotg->dev, irq, dwc2_hsotg_irq, IRQF_SHARED,
 				dev_name(hsotg->dev), hsotg);
 	if (ret < 0) {