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: 890954bdc8d0 ("usb: cdns3: Add Cadence USB3 DRD Driver")
cc: <stable@vger.kernel.org> # 5.4.x
Tested-by: Aswath Govindraju <a-govindraju@ti.com>
Reviewed-by: Aswath Govindraju <a-govindraju@ti.com>
Signed-off-by: Pawel Laszczak <pawell@cadence.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/usb/cdns3/gadget.c b/drivers/usb/cdns3/gadget.c
index c3bf54cc530f99a82b534ce7cf9f4639320c94be..296f2ee1b68031bb45844357a52b2d17bacd1d8b 100644 (file)
--- 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));
        }