Patch "usb: cdns3: fix race condition before setting doorbell" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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 the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     usb-cdns3-fix-race-condition-before-setting-doorbell.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit fd2649cc1dc7f357a445c02a6ed023258381f35d
Author: Pawel Laszczak <pawell@xxxxxxxxxxx>
Date:   Thu Sep 30 11:42:17 2021 +0200

    usb: cdns3: fix race condition before setting doorbell
    
    commit b69ec50b3e55c4b2a85c8bc46763eaf33060584 upstream
    
    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_STS_TRBERR can be set. In such case
    the transfer will not start after setting doorbell.
    
    Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver")
    cc: <stable@xxxxxxxxxxxxxxx> # 5.4.x
    Tested-by: Aswath Govindraju <a-govindraju@xxxxxx>
    Reviewed-by: Aswath Govindraju <a-govindraju@xxxxxx>
    Signed-off-by: Pawel Laszczak <pawell@xxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/usb/cdns3/gadget.c b/drivers/usb/cdns3/gadget.c
index c3bf54cc530f..296f2ee1b680 100644
--- a/drivers/usb/cdns3/gadget.c
+++ b/drivers/usb/cdns3/gadget.c
@@ -807,6 +807,19 @@ static void cdns3_wa1_tray_restore_cycle_bit(struct cdns3_device *priv_dev,
 		cdns3_wa1_restore_cycle_bit(priv_ep);
 }
 
+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
@@ -1003,6 +1016,7 @@ 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));
 	}