linux-kernel - [PATCH 6/6] usb: chipidea: udc: Add xilinx revision support

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Date:   Tue, 24 Aug 2021 22:46:18 +0530
From:   Manish Narani <manish.narani@...inx.com>
To:     <peter.chen@...nel.org>, <gregkh@...uxfoundation.org>,
        <michal.simek@...inx.com>
CC:     <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <git@...inx.com>, Piyush Mehta <piyush.mehta@...inx.com>,
        Manish Narani <manish.narani@...inx.com>
Subject: [PATCH 6/6] usb: chipidea: udc: Add xilinx revision support

From: Piyush Mehta <piyush.mehta@...inx.com>

Issue: Adding a dTD to a Primed Endpoint May Not Get Recognized with
revision 2.20a.

There is an issue with 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. When this happens, the software can read
the tripwire bit and the status bit at '1' even though the endpoint is
unprimed.
This issue observed with the Windows host machine.

Workaround:
The software must implement a periodic cycle, and check for each dTD
pending on execution (Active = 1), 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] along with 2.40.

Signed-off-by: Piyush Mehta <piyush.mehta@...inx.com>
Signed-off-by: Manish Narani <manish.narani@...inx.com>
---
 drivers/usb/chipidea/udc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/chipidea/udc.c b/drivers/usb/chipidea/udc.c
index 8834ca6..b440205 100644
--- a/drivers/usb/chipidea/udc.c
+++ b/drivers/usb/chipidea/udc.c
@@ -680,7 +680,8 @@ static int _hardware_dequeue(struct ci_hw_ep *hwep, struct ci_hw_req *hwreq)
 		if ((TD_STATUS_ACTIVE & tmptoken) != 0) {
 			int n = hw_ep_bit(hwep->num, hwep->dir);

-			if (ci->rev == CI_REVISION_24)
+			if (ci->rev == CI_REVISION_24 ||
+			    ci->rev == CI_REVISION_22)
 				if (!hw_read(ci, OP_ENDPTSTAT, BIT(n)))
 					reprime_dtd(ci, hwep, node);
 			hwreq->req.status = -EALREADY;
-- 
2.1.1