linux-kernel - Re: [PATCH] usb: dwc3: core: Disable USB2 retry for DWC

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Message-ID: <20241203010617.tfpguvbnmbi2xmnh@synopsys.com>
Date: Tue, 3 Dec 2024 01:06:19 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Faisal Hassan <quic_faisalh@...cinc.com>
CC: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: dwc3: core: Disable USB2 retry for DWC_usb31 1.80a
 and prior

On Fri, Nov 29, 2024, Faisal Hassan wrote:
> STAR 9001346572 addresses a USB 2.0 endpoint blocking issue in host mode
> for controller versions DWC_usb31 1.70a and 1.80a. This issue affects
> devices on both high-speed and full-speed bus instances. When all
> endpoint caches are filled and a single active endpoint receives
> continuous NAK responses, data transfers to other endpoints may get
> blocked.
> 
> To resolve this, for controller versions DWC_usb31 1.70a and 1.80a, the
> GUCTL3 bit[16] (USB2.0 Internal Retry Disable) is set to 1. This bit
> disables the USB2.0 internal retry feature and ensures proper eviction
> handling in the host controller endpoind cache. The GUCTL3[16] register
> function is available only from DWC_usb31 version 1.70a.
> 
> Signed-off-by: Faisal Hassan <quic_faisalh@...cinc.com>
> ---
>  drivers/usb/dwc3/core.c | 20 ++++++++++++++++++++
>  drivers/usb/dwc3/core.h |  1 +
>  2 files changed, 21 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 98114c2827c0..c5c36134ddd9 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -1475,6 +1475,26 @@ static int dwc3_core_init(struct dwc3 *dwc)
>  		dwc3_writel(dwc->regs, DWC3_LLUCTL, reg);
>  	}
>  
> +	/*
> +	 * STAR 9001346572: This issue affects DWC_usb31 versions 1.80a and
> +	 * prior. When an active endpoint not currently cached in the host
> +	 * controller is chosen to be cached to the same index as an endpoint
> +	 * receiving NAKs, the endpoint receiving NAKs enters continuous
> +	 * retry mode. This prevents it from being evicted from the host
> +	 * controller cache, blocking the new endpoint from being cached and
> +	 * serviced.
> +	 *
> +	 * To resolve this, for controller versions 1.70a and 1.80a, set the
> +	 * GUCTL3 bit[16] (USB2.0 Internal Retry Disable) to 1. This bit
> +	 * disables the USB2.0 internal retry feature. The GUCTL3[16] register
> +	 * function is available only from version 1.70a.
> +	 */
> +	if (DWC3_VER_IS_WITHIN(DWC31, 170A, 180A)) {
> +		reg = dwc3_readl(dwc->regs, DWC3_GUCTL3);
> +		reg |= DWC3_GUCTL3_USB20_RETRY_DISABLE;
> +		dwc3_writel(dwc->regs, DWC3_GUCTL3, reg);
> +	}
> +
>  	return 0;
>  
>  err_power_off_phy:
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index eab81dfdcc35..5417058c5943 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -425,6 +425,7 @@
>  
>  /* Global User Control Register 3 */
>  #define DWC3_GUCTL3_SPLITDISABLE		BIT(14)
> +#define DWC3_GUCTL3_USB20_RETRY_DISABLE		BIT(16)
>  
>  /* Device Configuration Register */
>  #define DWC3_DCFG_NUMLANES(n)	(((n) & 0x3) << 30) /* DWC_usb32 only */
> -- 
> 2.17.1
> 

Acked-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>

Thanks,
Thinh