linux-kernel - [PATCH 2/2] usb: gadget: u_serial: improve performance for large data

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Date:   Tue, 16 Jun 2020 20:34:44 +0800
From:   Macpaul Lin <macpaul.lin@...iatek.com>
To:     Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Sergey Organov <sorganov@...il.com>,
        Fabrice Gasnier <fabrice.gasnier@...com>,
        <linux-usb@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
CC:     Mediatek WSD Upstream <wsd_upstream@...iatek.com>,
        Macpaul Lin <macpaul.lin@...iatek.com>,
        Macpaul Lin <macpaul.lin@...il.com>
Subject: [PATCH 2/2] usb: gadget: u_serial: improve performance for large data

If the hardware (like DMA engine) could support large usb request exceeds
maximum packet size, use larger buffer when performing Rx/Tx could reduce
request numbers and improve performance.

Signed-off-by: Macpaul Lin <macpaul.lin@...iatek.com>
---
 drivers/usb/gadget/function/u_serial.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
index 3cfc6e2..cdcc070 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -80,6 +80,8 @@
 #define QUEUE_SIZE		16
 #define WRITE_BUF_SIZE		8192		/* TX only */
 #define GS_CONSOLE_BUF_SIZE	8192
+/* for hardware can do more than max packet */
+#define REQ_BUF_SIZE		4096
 
 /* console info */
 struct gs_console {
@@ -247,7 +249,8 @@ 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, in->can_exceed_maxp ?
+				REQ_BUF_SIZE : in->maxpacket);
 		if (len == 0) {
 			wake_up_interruptible(&port->drain_wait);
 			break;
@@ -514,7 +517,9 @@ 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, ep->can_exceed_maxp ?
+					REQ_BUF_SIZE : ep->maxpacket,
+					GFP_ATOMIC);
 		if (!req)
 			return list_empty(head) ? -ENOMEM : 0;
 		req->complete = fn;
-- 
1.7.9.5