linux-kernel - Re: [PATCH v1 1/2] xhci: Add a quirk for full reset on removal

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Message-ID: <2025051501-civil-module-63fa@gregkh>
Date: Thu, 15 May 2025 09:31:44 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Roy Luo <royluo@...gle.com>
Cc: mathias.nyman@...el.com, quic_ugoswami@...cinc.com,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/2] xhci: Add a quirk for full reset on removal

On Thu, May 15, 2025 at 04:02:07AM +0000, Roy Luo wrote:
> Commit 6ccb83d6c497 ("usb: xhci: Implement xhci_handshake_check_state()
> helper") introduced an optimization to xhci_reset() during xhci removal,
> allowing it to bail out early without waiting for the reset to complete.
> 
> This behavior can cause issues on SNPS DWC3 USB controller with dual-role
> capability. When the DWC3 controller exits host mode and removes xhci
> while a reset is still in progress, and then tries to configure its
> hardware for device mode, the ongoing reset leads to register access
> issues; specifically, all register reads returns 0. These issues extend
> beyond the xhci register space (which is expected during a reset) and
> affect the entire DWC3 IP block, causing the DWC3 device mode to
> malfunction.
> 
> To address this, introduce the `XHCI_FULL_RESET_ON_REMOVE` quirk. When this
> quirk is set, xhci_reset() always completes its reset handshake, ensuring
> the controller is in a fully reset state before proceeding.
> 
> Fixes: 6ccb83d6c497 ("usb: xhci: Implement xhci_handshake_check_state() helper")
> Signed-off-by: Roy Luo <royluo@...gle.com>
> ---
>  drivers/usb/host/xhci-plat.c | 3 +++
>  drivers/usb/host/xhci.c      | 8 +++++++-
>  drivers/usb/host/xhci.h      | 1 +
>  3 files changed, 11 insertions(+), 1 deletion(-)

For some reason this is not "attached" to patch 2 as a series, how did
you send this?  Did git-send-email not work properly for you?

thanks,

greg k-h