Re: [PATCH v2 2/6] usb: xhci: tegra: Remove redundant mutex when setting phy mode

From: Thierry Reding <thierry.reding@kernel.org>
To: Diogo Ivo <diogo.ivo@tecnico.ulisboa.pt>
Cc: Mathias Nyman <mathias.nyman@intel.com>,
	 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Thierry Reding <thierry.reding@gmail.com>,
	 Jonathan Hunter <jonathanh@nvidia.com>,
	JC Kuo <jckuo@nvidia.com>, Vinod Koul <vkoul@kernel.org>,
	 Kishon Vijay Abraham I <kishon@kernel.org>,
	Rob Herring <robh@kernel.org>,
	 Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	 Neil Armstrong <neil.armstrong@linaro.org>,
	linux-usb@vger.kernel.org, linux-tegra@vger.kernel.org,
	 linux-kernel@vger.kernel.org, linux-phy@lists.infradead.org,
	devicetree@vger.kernel.org
Subject: Re: [PATCH v2 2/6] usb: xhci: tegra: Remove redundant mutex when setting phy mode
Date: Tue, 24 Mar 2026 12:48:27 +0100	[thread overview]
Message-ID: <acJ50sQraVmy4zXs@orome> (raw)
In-Reply-To: <20260127-diogo-tegra_phy-v2-2-787b9eed3ed5@tecnico.ulisboa.pt>

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On Tue, Jan 27, 2026 at 03:11:48PM +0000, Diogo Ivo wrote:
> As the PHY subsystem already synchronizes concurrent accesses to a PHY
> instance with a core-internal mutex remove the driver specific mutex
> synchronization.
> 
> Signed-off-by: Diogo Ivo <diogo.ivo@tecnico.ulisboa.pt>
> ---
> v1->v2:
> - New patch
> ---
>  drivers/usb/host/xhci-tegra.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c
> index 8b492871d21d..927861ca14f2 100644
> --- a/drivers/usb/host/xhci-tegra.c
> +++ b/drivers/usb/host/xhci-tegra.c
> @@ -1357,15 +1357,11 @@ static void tegra_xhci_id_work(struct work_struct *work)
>  
>  	dev_dbg(tegra->dev, "host mode %s\n", str_on_off(tegra->host_mode));
>  
> -	mutex_lock(&tegra->lock);
> -
>  	if (tegra->host_mode)
>  		phy_set_mode_ext(phy, PHY_MODE_USB_OTG, USB_ROLE_HOST);
>  	else
>  		phy_set_mode_ext(phy, PHY_MODE_USB_OTG, USB_ROLE_NONE);
>  
> -	mutex_unlock(&tegra->lock);
> -

It looks to me like the mutex here is trying to protect against
tegra->host_mode changing while we're setting a different mode. That
doesn't seem to be taken care of by the PHY internal mutex.

Thierry

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