usb: dwc3: gadget: Ignore Update Transfer cmd params

The controller doesn't check for Update Transfer command parameters
DEPCMDPAR{0,1,2}. Writing to these registers is unnecessary. Ignoring
this improves performance slightly by removing the register write
delay.

Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/997d9ebf38c6bba920d4ee77bd8c77bf81978a55.1638240306.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 00b3f19..f66baae 100644 (file)
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -331,9 +331,17 @@ int dwc3_send_gadget_ep_cmd(struct dwc3_ep *dep, unsigned int cmd,
                }
        }
 
-       dwc3_writel(dep->regs, DWC3_DEPCMDPAR0, params->param0);
-       dwc3_writel(dep->regs, DWC3_DEPCMDPAR1, params->param1);
-       dwc3_writel(dep->regs, DWC3_DEPCMDPAR2, params->param2);
+       /*
+        * For some commands such as Update Transfer command, DEPCMDPARn
+        * registers are reserved. Since the driver often sends Update Transfer
+        * command, don't write to DEPCMDPARn to avoid register write delays and
+        * improve performance.
+        */
+       if (DWC3_DEPCMD_CMD(cmd) != DWC3_DEPCMD_UPDATETRANSFER) {
+               dwc3_writel(dep->regs, DWC3_DEPCMDPAR0, params->param0);
+               dwc3_writel(dep->regs, DWC3_DEPCMDPAR1, params->param1);
+               dwc3_writel(dep->regs, DWC3_DEPCMDPAR2, params->param2);
+       }
 
        /*
         * Synopsys Databook 2.60a states in section 6.3.2.5.6 of that if we're