linux-kernel - Re: [PATCH] usb: dwc3: Fix timeout issue during controller enter/exit from halt state

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Message-ID: <20250201001506.jr3yw4twwr7zutzd@synopsys.com>
Date: Sat, 1 Feb 2025 00:15:09 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Selvarasu Ganesan <selvarasu.g@...sung.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "balbi@...com" <balbi@...com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jh0801.jung@...sung.com" <jh0801.jung@...sung.com>,
        "dh10.jung@...sung.com" <dh10.jung@...sung.com>,
        "naushad@...sung.com" <naushad@...sung.com>,
        "akash.m5@...sung.com" <akash.m5@...sung.com>,
        "h10.kim@...sung.com" <h10.kim@...sung.com>,
        "eomji.oh@...sung.com" <eomji.oh@...sung.com>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "thiagu.r@...sung.com" <thiagu.r@...sung.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: Fix timeout issue during controller enter/exit
 from halt state

On Fri, Jan 31, 2025, Selvarasu Ganesan wrote:
> There is a frequent timeout during controller enter/exit from halt state
> after toggling the run_stop bit by SW. This timeout occurs when
> performing frequent role switches between host and device, causing
> device enumeration issues due to the timeout. This issue was not present
> when USB2 suspend PHY was disabled by passing the SNPS quirks
> (snps,dis_u2_susphy_quirk and snps,dis_enblslpm_quirk) from the DTS.
> However, there is a requirement to enable USB2 suspend PHY by setting of
> GUSB2PHYCFG.ENBLSLPM and GUSB2PHYCFG.SUSPHY bits when controller starts
> in gadget or host mode results in the timeout issue.
> 
> This commit addresses this timeout issue by ensuring that the bits
> GUSB2PHYCFG.ENBLSLPM and GUSB2PHYCFG.SUSPHY are cleared before starting
> the dwc3_gadget_run_stop sequence and restoring them after the
> dwc3_gadget_run_stop sequence is completed.
> 
> Fixes: 72246da40f37 ("usb: Introduce DesignWare USB3 DRD Driver")
> Cc: stable@...r.kernel.org
> Signed-off-by: Selvarasu Ganesan <selvarasu.g@...sung.com>
> ---
>  drivers/usb/dwc3/gadget.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index d27af65eb08a..4a158f703d64 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -2629,10 +2629,25 @@ static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on)
>  {
>  	u32			reg;
>  	u32			timeout = 2000;
> +	u32			saved_config = 0;
>  
>  	if (pm_runtime_suspended(dwc->dev))
>  		return 0;
>  

Can you add some comments here that this was added through experiment
since it is not documented in the programming guide. It would be great
to also note which platform you used to test this with.

> +	reg = dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0));
> +	if (unlikely(reg & DWC3_GUSB2PHYCFG_SUSPHY)) {

I know we have "unlikely" in the other check, but we should not need it
here or the other place. Please remove this here.

> +		saved_config |= DWC3_GUSB2PHYCFG_SUSPHY;
> +		reg &= ~DWC3_GUSB2PHYCFG_SUSPHY;
> +	}
> +
> +	if (reg & DWC3_GUSB2PHYCFG_ENBLSLPM) {
> +		saved_config |= DWC3_GUSB2PHYCFG_ENBLSLPM;
> +		reg &= ~DWC3_GUSB2PHYCFG_ENBLSLPM;
> +	}
> +
> +	if (saved_config)
> +		dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), reg);
> +
>  	reg = dwc3_readl(dwc->regs, DWC3_DCTL);
>  	if (is_on) {
>  		if (DWC3_VER_IS_WITHIN(DWC3, ANY, 187A)) {
> @@ -2660,6 +2675,12 @@ static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on)
>  		reg &= DWC3_DSTS_DEVCTRLHLT;
>  	} while (--timeout && !(!is_on ^ !reg));
>  
> +	if (saved_config) {
> +		reg = dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0));
> +		reg |= saved_config;
> +		dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), reg);
> +	}
> +
>  	if (!timeout)
>  		return -ETIMEDOUT;
>  
> -- 
> 2.17.1
> 

Thanks,
Thinh