linux-kernel - Re: [PATCH] usb: dwc3: gadget: fix writing NYET threshold

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Message-ID: <20241206192015.pwecvtssndjfi7qg@synopsys.com>
Date: Fri, 6 Dec 2024 19:20:23 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: André Draszik <andre.draszik@...aro.org>
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: gadget: fix writing NYET threshold

On Fri, Dec 06, 2024, André Draszik wrote:
> Before writing a new value to the register, the old value needs to be
> masked out for the new value to be programmed as intended.
> 
> At the moment, the dwc3 core initialises the threshold to the maximum
> value (0xf), with the option to override it via a DT. No upstream DTs
> seem to override it, therefore this commit doesn't change behaviour for
> any upstream platform. Nevertheless, the code should be fixed to have
> the desired outcome.
> 
> Do so.
> 
> Signed-off-by: André Draszik <andre.draszik@...aro.org>
> ---
>  drivers/usb/dwc3/core.h   | 1 +
>  drivers/usb/dwc3/gadget.c | 4 +++-
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
> index ee73789326bc..9335fd095968 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -465,6 +465,7 @@
>  
>  /* These apply for core versions 1.94a and later */
>  #define DWC3_DCTL_NYET_THRES(n)		(((n) & 0xf) << 20)
> +#define DWC3_DCTL_NYET_THRES_MASK	DWC3_DCTL_NYET_THRES(0xf)

If you're going to define a mask macro this way, do this:
DWC3_DCTL_NYET_THRES(~0)

>  
>  #define DWC3_DCTL_KEEP_CONNECT		BIT(19)
>  #define DWC3_DCTL_L1_HIBER_EN		BIT(18)
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 83dc7304d701..31a654c6f15b 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -4195,8 +4195,10 @@ static void dwc3_gadget_conndone_interrupt(struct dwc3 *dwc)
>  		WARN_ONCE(DWC3_VER_IS_PRIOR(DWC3, 240A) && dwc->has_lpm_erratum,
>  				"LPM Erratum not available on dwc3 revisions < 2.40a\n");
>  
> -		if (dwc->has_lpm_erratum && !DWC3_VER_IS_PRIOR(DWC3, 240A))
> +		if (dwc->has_lpm_erratum && !DWC3_VER_IS_PRIOR(DWC3, 240A)) {
> +			reg &= ~DWC3_DCTL_NYET_THRES_MASK;
>  			reg |= DWC3_DCTL_NYET_THRES(dwc->lpm_nyet_threshold);
> +		}
>  
>  		dwc3_gadget_dctl_write_safe(dwc, reg);
>  	} else {
> 
> ---
> base-commit: c245a7a79602ccbee780c004c1e4abcda66aec32
> change-id: 20241206-dwc3-nyet-fix-7085f6d71d04
> 
> Best regards,
> -- 
> André Draszik <andre.draszik@...aro.org>
> 

Can you also include a fixes tag and Cc stable?

Thanks,
Thinh