linux-kernel - [PATCH v2 04/25] usb: gadget: f

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Date:   Mon, 18 Jul 2022 18:26:29 -0700
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dmitry Bogdanov <d.bogdanov@...ro.com>
Cc:     linux-scsi@...r.kernel.org, target-devel@...r.kernel.org
Subject: [PATCH v2 04/25] usb: gadget: f_tcm: Increase bMaxBurst

Currently the default bMaxBurst is 0. Set default bMaxBurst to 15 (i.e.
16 bursts) to Data IN and OUT endpoints to improve performance. It
should be fine for a controller that supports less than 16 bursts. It
should be able to negotiate properly with the host at packet level for
the end of burst.

If the controller can't handle a burst of 16, and high performance isn't
important, the user can use BOT protocol from mass_storage gadget driver
instead.

Signed-off-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
---
 Changes in v2:
 - None

 drivers/usb/gadget/function/f_tcm.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_tcm.c b/drivers/usb/gadget/function/f_tcm.c
index 8e17ac831be0..270ec631481d 100644
--- a/drivers/usb/gadget/function/f_tcm.c
+++ b/drivers/usb/gadget/function/f_tcm.c
@@ -1774,7 +1774,7 @@ static struct usb_endpoint_descriptor uasp_ss_bi_desc = {
 static struct usb_ss_ep_comp_descriptor uasp_bi_ep_comp_desc = {
 	.bLength =		sizeof(uasp_bi_ep_comp_desc),
 	.bDescriptorType =	USB_DT_SS_ENDPOINT_COMP,
-	.bMaxBurst =		0,
+	.bMaxBurst =		15,
 	.bmAttributes =		UASP_SS_EP_COMP_LOG_STREAMS,
 	.wBytesPerInterval =	0,
 };
@@ -1782,7 +1782,7 @@ static struct usb_ss_ep_comp_descriptor uasp_bi_ep_comp_desc = {
 static struct usb_ss_ep_comp_descriptor bot_bi_ep_comp_desc = {
 	.bLength =		sizeof(bot_bi_ep_comp_desc),
 	.bDescriptorType =	USB_DT_SS_ENDPOINT_COMP,
-	.bMaxBurst =		0,
+	.bMaxBurst =		15,
 };
 
 static struct usb_endpoint_descriptor uasp_bo_desc = {
@@ -1817,12 +1817,14 @@ static struct usb_endpoint_descriptor uasp_ss_bo_desc = {
 static struct usb_ss_ep_comp_descriptor uasp_bo_ep_comp_desc = {
 	.bLength =		sizeof(uasp_bo_ep_comp_desc),
 	.bDescriptorType =	USB_DT_SS_ENDPOINT_COMP,
+	.bMaxBurst =		15,
 	.bmAttributes =		UASP_SS_EP_COMP_LOG_STREAMS,
 };
 
 static struct usb_ss_ep_comp_descriptor bot_bo_ep_comp_desc = {
 	.bLength =		sizeof(bot_bo_ep_comp_desc),
 	.bDescriptorType =	USB_DT_SS_ENDPOINT_COMP,
+	.bMaxBurst =		15,
 };
 
 static struct usb_endpoint_descriptor uasp_status_desc = {
-- 
2.28.0