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.

Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver")
cc: <stable@vger.kernel.org> # 5.12.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>
Link: https://lore.kernel.org/r/20210907062619.34622-1-pawell@gli-login.cadence.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/cdns3/cdns3-gadget.c b/drivers/usb/cdns3/cdns3-gadget.c
index 5d8c982019afc2e78db9cf8eb11984481445e52b..1f3b4a1422126bff26011c4ff7fd48bfa1f38e8c 100644 (file)
--- a/drivers/usb/cdns3/cdns3-gadget.c
+++ b/drivers/usb/cdns3/cdns3-gadget.c
@@ -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));
        }