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From:   Piyush Mehta <piyushm@xilinx.com>
To:     Piyush Mehta <piyushm@xilinx.com>,
        "peter.chen@kernel.org" <peter.chen@kernel.org>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
CC:     "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        git <git@xilinx.com>, Srinivas Goud <sgoud@xilinx.com>,
        Michal Simek <michals@xilinx.com>
Subject: RE: [PATCH V2] usb: chipidea: udc: make controller hardware endpoint
 primed
Thread-Topic: [PATCH V2] usb: chipidea: udc: make controller hardware endpoint
 primed
Thread-Index: AQHXqKfGANk7ocKDUUW0VmeorsQa/avFhiAQ
Date:   Wed, 6 Oct 2021 04:36:59 +0000
Message-ID: <SJ0PR02MB864445907305B66580FFE1D8D4B09@SJ0PR02MB8644.namprd02.prod.outlook.com>
References: <20210913140005.955699-1-piyush.mehta@xilinx.com>
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Ping ...

Regards,
Piyush Mehta

-----Original Message-----
From: Piyush Mehta <piyush.mehta@xilinx.com>=20
Sent: Monday, September 13, 2021 7:30 PM
To: peter.chen@kernel.org; gregkh@linuxfoundation.org
Cc: linux-usb@vger.kernel.org; linux-kernel@vger.kernel.org; git <git@xilin=
x.com>; Srinivas Goud <sgoud@xilinx.com>; Michal Simek <michals@xilinx.com>=
; Piyush Mehta <piyushm@xilinx.com>
Subject: [PATCH V2] usb: chipidea: udc: make controller hardware endpoint p=
rimed

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 regis=
ter) that can cause the controller to ignore a dTD that is added to a prime=
d endpoint.
This issue observed with the Windows10 host machine.

Workaround:
The software must implement a periodic cycle, and check for each dTD, if th=
e endpoint is primed. It can do this by reading the corresponding bits in t=
he ENDPTPRIME and ENDPTSTAT registers. If these bits are read at 0, the sof=
tware 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@xilinx.com>
---
Changes for V2:
- Addressed Peter review comments - Remove unrelated new-line
- Updated commit message

Link: https://lore.kernel.org/linux-usb/SJ0PR02MB8644CBBA848A0F68323F1AA5D4=
D99@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 =3D {
 	.wMaxPacketSize  =3D cpu_to_le16(CTRL_PAYLOAD_MAX),  };
=20
+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, st=
ruct ci_hw_req *hwreq)
=20
 		prevlastnode->ptr->next =3D cpu_to_le32(next);
 		wmb();
+
+		if (ci->rev =3D=3D 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