linux-kernel - Re: [PATCH v2, 3/3] usb: dwc3: core: Workaround for CSR read timeout

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Date: Tue, 4 Jun 2024 00:07:29 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: joswang <joswang1221@...il.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "robh@...nel.org" <robh@...nel.org>,
        "krzk+dt@...nel.org" <krzk+dt@...nel.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        joswang <joswang@...ovo.com>
Subject: Re: [PATCH v2, 3/3] usb: dwc3: core: Workaround for CSR read timeout

On Mon, Jun 03, 2024, joswang wrote:
> From: joswang <joswang@...ovo.com>
> 
> DWC31 version 2.00a have an issue that would cause
> a CSR read timeout When CSR read coincides with RAM
> Clock Gating Entry.

Do you have the STAR issue number?

> 
> This workaround solution disable Clock Gating, sacrificing
> power consumption for normal operation.
> 
> Signed-off-by: joswang <joswang@...ovo.com>
> ---
>  drivers/usb/dwc3/core.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 3a8fbc2d6b99..1df85c505c9e 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -978,11 +978,22 @@ static void dwc3_core_setup_global_control(struct dwc3 *dwc)
>  		 *
>  		 * STAR#9000588375: Clock Gating, SOF Issues when ref_clk-Based
>  		 * SOF/ITP Mode Used
> +		 *
> +		 * WORKAROUND: DWC31 version 2.00a have an issue that would
> +		 * cause a CSR read timeout When CSR read coincides with RAM
> +		 * Clock Gating Entry.
> +		 *
> +		 * This workaround solution disable Clock Gating, sacrificing
> +		 * power consumption for normal operation.
>  		 */
>  		if ((dwc->dr_mode == USB_DR_MODE_HOST ||
>  				dwc->dr_mode == USB_DR_MODE_OTG) &&
>  				DWC3_VER_IS_WITHIN(DWC3, 210A, 250A))
>  			reg |= DWC3_GCTL_DSBLCLKGTNG | DWC3_GCTL_SOFITPSYNC;
> +		else if ((dwc->dr_mode == USB_DR_MODE_HOST ||
> +				dwc->dr_mode == USB_DR_MODE_OTG) &&
> +				DWC3_VER_IS(DWC31, 200A))
> +			reg |= DWC3_GCTL_DSBLCLKGTNG;
>  		else
>  			reg &= ~DWC3_GCTL_DSBLCLKGTNG;
>  		break;
> @@ -992,6 +1003,18 @@ static void dwc3_core_setup_global_control(struct dwc3 *dwc)
>  		 * will work. Device-mode hibernation is not yet implemented.
>  		 */
>  		reg |= DWC3_GCTL_GBLHIBERNATIONEN;
> +
> +		/*
> +		 * WORKAROUND: DWC31 version 2.00a have an issue that would
> +		 * cause a CSR read timeout When CSR read coincides with RAM
> +		 * Clock Gating Entry.
> +		 *
> +		 * This workaround solution disable Clock Gating, sacrificing
> +		 * power consumption for normal operation.
> +		 */
> +		if ((dwc->dr_mode == USB_DR_MODE_HOST ||
> +		     dwc->dr_mode == USB_DR_MODE_OTG) && DWC3_VER_IS(DWC31, 200A))
> +			reg |= DWC3_GCTL_DSBLCLKGTNG;
>  		break;
>  	default:
>  		/* nothing */
> -- 
> 2.17.1
> 

This doesn't seem like it should be applied globally. Please provide the
STAR number if you can so I can review further. If possible I'd prefer
to only target your platform.

Thanks,
Thinh