patch "usb: cdns3: fix race condition before setting doorbell" added to usb-linus

This is a note to let you know that I've just added the patch titled

usb: cdns3: fix race condition before setting doorbell

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From b69ec50b3e55c4b2a85c8bc46763eaf330605847 Mon Sep 17 00:00:00 2001
From: Pawel Laszczak <[email protected]>
Date: Tue, 7 Sep 2021 08:26:19 +0200
Subject: usb: cdns3: fix race condition before setting doorbell

For DEV_VER_V3 version there exist race condition between clearing ep_sts.EP_STS_TRBERR and setting ep_cmd.EP_CMD_DRDY bit. Setting EP_CMD_DRDY will be ignored by controller when EP_STS_TRBERR is set. So, between these two instructions we have a small time gap in which the EP_STSS_TRBERR can be set. In such case the transfer will not start after setting doorbell.

---
 drivers/usb/cdns3/cdns3-gadget.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

index 5d8c982019af..1f3b4a142212 100644
@@ -1100,6 +1100,19 @@ static int cdns3_ep_run_stream_transfer(struct cdns3_endpoint *priv_ep,
 	return 0;
 }
 
+static void cdns3_rearm_drdy_if_needed(struct cdns3_endpoint *priv_ep)
+{
+	struct cdns3_device *priv_dev = priv_ep->cdns3_dev;
+
+	if (priv_dev->dev_ver < DEV_VER_V3)
+		return;
+
+	if (readl(&priv_dev->regs->ep_sts) & EP_STS_TRBERR) {
+		writel(EP_STS_TRBERR, &priv_dev->regs->ep_sts);
+		writel(EP_CMD_DRDY, &priv_dev->regs->ep_cmd);
+	}
+}
+
 /**
  * cdns3_ep_run_transfer - start transfer on no-default endpoint hardware
  * @priv_ep: endpoint object

@@ -1351,6 +1364,7 @@ static int cdns3_ep_run_transfer(struct cdns3_endpoint *priv_ep,
 		/*clearing TRBERR and EP_STS_DESCMIS before seting DRDY*/
 		writel(EP_STS_TRBERR | EP_STS_DESCMIS, &priv_dev->regs->ep_sts);
 		writel(EP_CMD_DRDY, &priv_dev->regs->ep_cmd);
+		cdns3_rearm_drdy_if_needed(priv_ep);
 		trace_cdns3_doorbell_epx(priv_ep->name,
 					 readl(&priv_dev->regs->ep_traddr));
 	}

2.33.0