linux-kernel - RE: [PATCH V2] usb: chipidea: udc: make controller hardware endpoint primed

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Date:   Wed, 6 Oct 2021 04:36:59 +0000
From:   Piyush Mehta <piyushm@...inx.com>
To:     Piyush Mehta <piyushm@...inx.com>,
        "peter.chen@...nel.org" <peter.chen@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        git <git@...inx.com>, Srinivas Goud <sgoud@...inx.com>,
        Michal Simek <michals@...inx.com>
Subject: RE: [PATCH V2] usb: chipidea: udc: make controller hardware endpoint
 primed

Ping ...

Regards,
Piyush Mehta

-----Original Message-----
From: Piyush Mehta <piyush.mehta@...inx.com> 
Sent: Monday, September 13, 2021 7:30 PM
To: peter.chen@...nel.org; gregkh@...uxfoundation.org
Cc: linux-usb@...r.kernel.org; linux-kernel@...r.kernel.org; git <git@...inx.com>; Srinivas Goud <sgoud@...inx.com>; Michal Simek <michals@...inx.com>; Piyush Mehta <piyushm@...inx.com>
Subject: [PATCH V2] usb: chipidea: udc: make controller hardware endpoint primed

Root-cause:
There is an issue like endpoint is not recognized as primed, when bus have more pressure and the add dTD tripwire semaphore (ATDTW bit in USBCMD register) that can cause the controller to ignore a dTD that is added to a primed endpoint.
This issue observed with the Windows10 host machine.

Workaround:
The software must implement a periodic cycle, and check for each dTD, if the endpoint is primed. It can do this by reading the corresponding bits in the ENDPTPRIME and ENDPTSTAT registers. If these bits are read at 0, the software needs to re-prime the endpoint by writing 1 to the corresponding bit in the ENDPTPRIME register.

Added conditional revision check of 2.20[CI_REVISION_22].

Signed-off-by: Piyush Mehta <piyush.mehta@...inx.com>
---
Changes for V2:
- Addressed Peter review comments - Remove unrelated new-line
- Updated commit message

Link: https://lore.kernel.org/linux-usb/SJ0PR02MB8644CBBA848A0F68323F1AA5D4D99@SJ0PR02MB8644.namprd02.prod.outlook.com/
---
 drivers/usb/chipidea/udc.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/usb/chipidea/udc.c b/drivers/usb/chipidea/udc.c index 8834ca6..f9ca501 100644
--- a/drivers/usb/chipidea/udc.c
+++ b/drivers/usb/chipidea/udc.c
@@ -49,6 +49,8 @@ ctrl_endpt_in_desc = {
 	.wMaxPacketSize  = cpu_to_le16(CTRL_PAYLOAD_MAX),  };
 
+static int reprime_dtd(struct ci_hdrc *ci, struct ci_hw_ep *hwep,
+		       struct td_node *node);
 /**
  * hw_ep_bit: calculates the bit number
  * @num: endpoint number
@@ -599,6 +601,12 @@ static int _hardware_enqueue(struct ci_hw_ep *hwep, struct ci_hw_req *hwreq)
 
 		prevlastnode->ptr->next = cpu_to_le32(next);
 		wmb();
+
+		if (ci->rev == CI_REVISION_22) {
+			if (!hw_read(ci, OP_ENDPTSTAT, BIT(n)))
+				reprime_dtd(ci, hwep, prevlastnode);
+		}
+
 		if (hw_read(ci, OP_ENDPTPRIME, BIT(n)))
 			goto done;
 		do {
--
2.7.4