Patch "usb: dwc3: xilinx: Skip resets and USB3 register settings for USB2.0 mode" has been added to the 5.16-stable tree

This is a note to let you know that I've just added the patch titled

usb: dwc3: xilinx: Skip resets and USB3 register settings for USB2.0 mode

to the 5.16-stable tree which can be found at:

https://urldefense.com/v3/__http://www.kernel.org/git/?p=linux*kernel*git*stable*stable-queue.git;a=summary__;Ly8vLw!!IOGos0k!zf9QJvY84EtqUpdi6VflkIp1CJqnnCaQoiGGvZ8KORysjiM44hQecYjVySxsuD6OjZA$

The filename of the patch is:
usb-dwc3-xilinx-skip-resets-and-usb3-register-settings-for-usb2.0-
mode.patch
and it can be found in the queue-5.16 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From 9678f3361afc27a3124cd2824aec0227739986fb Mon Sep 17 00:00:00 2001
From: Robert Hancock <[email protected]>
Date: Tue, 25 Jan 2022 18:02:50 -0600
Subject: usb: dwc3: xilinx: Skip resets and USB3 register settings for USB2.0 mode

From: Robert Hancock <[email protected]>

commit 9678f3361afc27a3124cd2824aec0227739986fb upstream.

It appears that the PIPE clock should not be selected when only USB 2.0 is being used in the design and no USB 3.0 reference clock is used. Also, the core resets are not required if a USB3 PHY is not in use, and will break things if USB3 is actually used but the PHY entry is not listed in the device tree.

Skip core resets and register settings that are only required for USB3 mode when no USB3 PHY is specified in the device tree.

Fixes 84770f028fab ("usb: dwc3: Add driver for Xilinx platforms")

Cc stable <[email protected]>

Signed-off-by Robert Hancock <[email protected]>

Link:
https://urldefense.com/v3/__https://lore.kernel.org/r/[email protected]__;!!IOGos0k!zf9QJvY84EtqUpdi6VflkIp1CJqnnCaQoiGGvZ8KORysjiM44hQecYjVySxsMI6yBj4$

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 drivers/usb/dwc3/dwc3-xilinx.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

drivers/usb/dwc3/dwc3-xilinx.c +13 -0

@@ -110,6 +110,18 @@ static int dwc3_xlnx_init_zynqmp(struct
 		usb3_phy = NULL;
 	}
 
+	/*
+	 * The following core resets are not required unless a USB3 PHY
+	 * is used, and the subsequent register settings are not required
+	 * unless a core reset is performed (they should be set properly
+	 * by the first-stage boot loader, but may be reverted by a core
+	 * reset). They may also break the configuration if USB3 is actually
+	 * in use but the usb3-phy entry is missing from the device tree.
+	 * Therefore, skip these operations in this case.
+	 */
+	if (!usb3_phy)
+		goto skip_usb3_phy;
+
 	crst = devm_reset_control_get_exclusive(dev, "usb_crst");
 	if (IS_ERR(crst)) {
 		ret = PTR_ERR(crst);

@@ -188,6 +200,7 @@ static int dwc3_xlnx_init_zynqmp(struct
 		goto err;
 	}
 
+skip_usb3_phy:
 	/*
 	 * This routes the USB DMA traffic to go through FPD path instead
 	 * of reaching DDR directly. This traffic routing is needed to

Patches currently in stable-queue which might be from [email protected] are

queue-5.16/serial-8250-of-fix-mapped-region-size-when-using-reg-offset- property.patch queue-5.16/usb-dwc3-xilinx-skip-resets-and-usb3-register-settings-for-usb2.0- mode.patch queue-5.16/usb-dwc3-xilinx-fix-error-handling-when-getting-usb3-phy.patch

Quoted 9 lines · On Sat, 2022-01-29 at 17:24 +0100, [email protected] wrote:

This is a note to let you know that I've just added the patch titled

usb: dwc3: xilinx: Skip resets and USB3 register settings for USB2.0 mode

to the 5.16-stable tree which can be found at:

https://urldefense.com/v3/__http://www.kernel.org/git/?p=linux*kernel*git*stable*stable-queue.git;a=summary__;Ly8vLw!!IOGos0k!zf9QJvY84EtqUpdi6VflkIp1CJqnnCaQoiGGvZ8KORysjiM44hQecYjVySxsuD6OjZA$

Quoted 7 lines

The filename of the patch is:
usb-dwc3-xilinx-skip-resets-and-usb3-register-settings-for-usb2.0-
mode.patch
and it can be found in the queue-5.16 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Hi Greg,

This patch should likely only go into stable along with the follow-up patch I posted (or something equivalent):

https://patchwork.kernel.org/project/linux-usb/patch/[email protected]/

Otherwise it will cause a regression.