From a02a26eb0aeaa2859a8b2f182bd5b5f7228ee1fe Mon Sep 17 00:00:00 2001
From: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Date: Mon, 29 Nov 2021 18:53:16 -0800
Subject: [PATCH] usb: dwc3: gadget: Ignore Update Transfer cmd params
Git-commit: a02a26eb0aeaa2859a8b2f182bd5b5f7228ee1fe
References: git-fixes
Patch-mainline: v5.17-rc1

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>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/usb/dwc3/gadget.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 00b3f19c4d3e..f66baaef8a40 100644
--- 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
-- 
2.35.3