[PATCH v3] usb: gadget: u_serial: improve performance for large data

[Macpaul Lin]

Nowadays some embedded systems use VCOM to transfer large log and data.
Take LTE MODEM as an example, during the long debugging stage, large
log and data were transfer through VCOM when doing field try or in
operator's lab. Here we suggest slightly increase the transfer buffer
in u_serial.c for performance improving.

Signed-off-by: Macpaul Lin <macpaul.lin@xxxxxxxxxxxx>
---
Changes for v2:
  - Drop previous patch for adding flag which indicates hardware capability in
    gadget.h and in DMA engine according to Alan's suggestion. Thanks.
  - Replace requested buffer size "REQ_BUF_SIZE" instead of checking hardware
    capability.
  - Refine commit messages.
Changes for v3:
  - Code: no change.
    Commit: Add missing change log in v2.

 drivers/usb/gadget/function/u_serial.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index 3cfc6e2..d7912a9 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -80,6 +80,7 @@
 #define QUEUE_SIZE		16
 #define WRITE_BUF_SIZE		8192		/* TX only */
 #define GS_CONSOLE_BUF_SIZE	8192
+#define REQ_BUF_SIZE		4096
 
 /* console info */
 struct gs_console {
@@ -247,7 +248,7 @@ static int gs_start_tx(struct gs_port *port)
 			break;
 
 		req = list_entry(pool->next, struct usb_request, list);
-		len = gs_send_packet(port, req->buf, in->maxpacket);
+		len = gs_send_packet(port, req->buf, REQ_BUF_SIZE);
 		if (len == 0) {
 			wake_up_interruptible(&port->drain_wait);
 			break;
@@ -514,7 +515,7 @@ static int gs_alloc_requests(struct usb_ep *ep, struct list_head *head,
 	 * be as speedy as we might otherwise be.
 	 */
 	for (i = 0; i < n; i++) {
-		req = gs_alloc_req(ep, ep->maxpacket, GFP_ATOMIC);
+		req = gs_alloc_req(ep, REQ_BUF_SIZE, GFP_ATOMIC);
 		if (!req)
 			return list_empty(head) ? -ENOMEM : 0;
 		req->complete = fn;
-- 
1.7.9.5