linux-kernel - Re: [PATCH] usb: dwc3: fix fault at system suspend if device was already runtime suspended

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Message-ID: <ZykMvEXywBRuhZAM@google.com>
Date: Mon, 4 Nov 2024 10:04:44 -0800
From: William McVicker <willmcvicker@...gle.com>
To: Roger Quadros <rogerq@...nel.org>
Cc: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dhruva Gole <d-gole@...com>, sashal@...nel.org,
	Chris Morgan <macroalpha82@...il.com>,
	Vishal Mahaveer <vishalm@...com>, msp@...libre.com, srk@...com,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] usb: dwc3: fix fault at system suspend if device was
 already runtime suspended

Hi Roger,

On 11/04/2024, Roger Quadros wrote:
> If the device was already runtime suspended then during system suspend
> we cannot access the device registers else it will crash.
> 
> Also we cannot access any registers after dwc3_core_exit() on some
> platforms so move the dwc3_enable_susphy() call to the top.
> 
> Cc: stable@...r.kernel.org # v5.15+
> Reported-by: William McVicker <willmcvicker@...gle.com>
> Closes: https://lore.kernel.org/all/ZyVfcUuPq56R2m1Y@google.com
> Fixes: 705e3ce37bcc ("usb: dwc3: core: Fix system suspend on TI AM62 platforms")
> Signed-off-by: Roger Quadros <rogerq@...nel.org>

I verified the patch works on my Pixel 6 device with runtime PM enabled. Thanks
for the fix! Feel free to add

Tested-by: Will McVicker <willmcvicker@...gle.com>

Thanks,
Will

> ---
>  drivers/usb/dwc3/core.c | 25 ++++++++++++-------------
>  1 file changed, 12 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 427e5660f87c..98114c2827c0 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -2342,10 +2342,18 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
>  	u32 reg;
>  	int i;
>  
> -	dwc->susphy_state = (dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0)) &
> -			    DWC3_GUSB2PHYCFG_SUSPHY) ||
> -			    (dwc3_readl(dwc->regs, DWC3_GUSB3PIPECTL(0)) &
> -			    DWC3_GUSB3PIPECTL_SUSPHY);
> +	if (!pm_runtime_suspended(dwc->dev) && !PMSG_IS_AUTO(msg)) {
> +		dwc->susphy_state = (dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0)) &
> +				    DWC3_GUSB2PHYCFG_SUSPHY) ||
> +				    (dwc3_readl(dwc->regs, DWC3_GUSB3PIPECTL(0)) &
> +				    DWC3_GUSB3PIPECTL_SUSPHY);
> +		/*
> +		 * TI AM62 platform requires SUSPHY to be
> +		 * enabled for system suspend to work.
> +		 */
> +		if (!dwc->susphy_state)
> +			dwc3_enable_susphy(dwc, true);
> +	}
>  
>  	switch (dwc->current_dr_role) {
>  	case DWC3_GCTL_PRTCAP_DEVICE:
> @@ -2398,15 +2406,6 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
>  		break;
>  	}
>  
> -	if (!PMSG_IS_AUTO(msg)) {
> -		/*
> -		 * TI AM62 platform requires SUSPHY to be
> -		 * enabled for system suspend to work.
> -		 */
> -		if (!dwc->susphy_state)
> -			dwc3_enable_susphy(dwc, true);
> -	}
> -
>  	return 0;
>  }
>  
> 
> ---
> base-commit: 42f7652d3eb527d03665b09edac47f85fb600924
> change-id: 20241102-am62-lpm-usb-fix-347dd86135c1
> 
> Best regards,
> -- 
> Roger Quadros <rogerq@...nel.org>
>