linux-kernel - [PATCH] usb: dwc3: core: disable 3.0 clock when operating in 2.0 device mode

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Message-ID: <20231005102725.8458-1-piyush.mehta@amd.com>
Date:   Thu, 5 Oct 2023 15:57:25 +0530
From:   Piyush Mehta <piyush.mehta@....com>
To:     <gregkh@...uxfoundation.org>, <michal.simek@....com>,
        <Thinh.Nguyen@...opsys.com>, <robh@...nel.org>,
        <herve.codina@...tlin.com>, <yangbin@...k-chips.com>,
        <pgwipeout@...il.com>
CC:     <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <git@....com>, Piyush Mehta <piyush.mehta@....com>
Subject: [PATCH] usb: dwc3: core: disable 3.0 clock when operating in 2.0 device mode

The GUCTL1.DEV_FORCE_20_CLK_FOR_30_CLK bit enable the feature of internal
2.0(utmi/ulpi) clock to be routed as the 3.0 (pipe) clock. This feature is
applicable when core is operating in 2.0 device mode.

When this bit is set in host mode and core is in 2.0 device mode (maximum
speed = high-speed) then usb super speed devices not detected on host.

To address the above issue added usb device mode conditional check.

Fixes: 62b20e6e0dde ("usb: dwc3: core: do not use 3.0 clock when operating in 2.0 mode")
Signed-off-by: Piyush Mehta <piyush.mehta@....com>
---
DWC3 Register Map Link:
https://docs.xilinx.com/r/en-US/ug1087-zynq-ultrascale-registers/GUCTL1-USB3_XHCI-Register
Register Name	GUCTL1
Bit: 26 
Bit Name: DEV_FORCE_20_CLK_FOR_30_CLK
---
 drivers/usb/dwc3/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 9c6bf054f15d..0cf1fe60628b 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -1202,6 +1202,7 @@ static int dwc3_core_init(struct dwc3 *dwc)
 			reg |= DWC3_GUCTL1_PARKMODE_DISABLE_HS;
 
 		if (DWC3_VER_IS_WITHIN(DWC3, 290A, ANY) &&
+		    (dwc->dr_mode == USB_DR_MODE_PERIPHERAL) &&
 		    (dwc->maximum_speed == USB_SPEED_HIGH ||
 		     dwc->maximum_speed == USB_SPEED_FULL))
 			reg |= DWC3_GUCTL1_DEV_FORCE_20_CLK_FOR_30_CLK;
-- 
2.17.1