usb: dwc2: gadget: Add DDMA isoc related fields to dwc2_hsotg_ep

Preparing for isochronous transfers support adding in DDMA mode. In DDMA
isochronous transfers are handled differently compared to Slave and BDMA
modes. This is caused by fact that isoc requests contain data for one
frame/microframe. HW descriptor should contain data of one
frame/microframe as well. Hence each DMA descriptor in the chain will
correspond to one usb request.

Decided to divide endpoints descriptor chain to two halves - while one
will be processed by HW, other one will be under SW control. First part
will be passed to HW once ISOC traffic needs to be started. In parallel
to HW's work SW will keep creating new entries in the other half of
chain if new requests arrive in ep_queue routine. This will allow
passing of already pre-prepared descriptors to HW immediately after
endpoint gets disabled. The endpoint should be disabled once HW closes
descriptor with "L" bit set. Afterwards SW will switch to use first part
of chain if more requests are arriving.

Add two members to the dwc2_hsotg_ep structure to be used in isochronous
transfers' handling in DDMA mode:

-isoc_chain_num - indicates which half of EP descriptor chain can be
		used by SW to add new queued requests while HW is
		processing other half.

-next_desc - index which points to next not yet programmed descriptor in
		the half of descriptor chain which is under SW control.

Also add initialization of these fields in function
dwc2_hsotg_ep_enable().
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

@@ -175,6 +175,8 @@ struct dwc2_hsotg_req;
  * @desc_list_dma: The DMA address of descriptor chain currently in use.
  * @desc_list: Pointer to descriptor DMA chain head currently in use.
  * @desc_count: Count of entries within the DMA descriptor chain of EP.
+ * @isoc_chain_num: Number of ISOC chain currently in use - either 0 or 1.
+ * @next_desc: index of next free descriptor in the ISOC chain under SW control.
  * @total_data: The total number of data bytes done.
  * @fifo_size: The size of the FIFO (for periodic IN endpoints)
  * @fifo_load: The amount of data loaded into the FIFO (periodic IN)
@@ -226,6 +228,9 @@ struct dwc2_hsotg_ep {
 	struct dwc2_dma_desc	*desc_list;
 	u8			desc_count;
 
+	unsigned char		isoc_chain_num;
+	unsigned int		next_desc;
+
 	char                    name[10];
 };
 

drivers/usb/dwc2/gadget.c

@@ -3356,6 +3356,8 @@ static int dwc2_hsotg_ep_enable(struct usb_ep *ep,
 		hs_ep->isochronous = 1;
 		hs_ep->interval = 1 << (desc->bInterval - 1);
 		hs_ep->target_frame = TARGET_FRAME_INITIAL;
+		hs_ep->isoc_chain_num = 0;
+		hs_ep->next_desc = 0;
 		if (dir_in) {
 			hs_ep->periodic = 1;
 			mask = dwc2_readl(hsotg->regs + DIEPMSK);