linux-kernel - Re: [PATCH v2] usb: dwc3: gadget: fix writing NYET threshold

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Message-ID: <20241210225122.5afdikznqgyweclc@synopsys.com>
Date: Tue, 10 Dec 2024 22:51:39 +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>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v2] usb: dwc3: gadget: fix writing NYET threshold

On Mon, Dec 09, 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, because at
> least in some cases the reset value of that field is 0xf (max value).
> 
> 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.
> 
> Fixes: 80caf7d21adc ("usb: dwc3: add lpm erratum support")
> Cc: stable@...r.kernel.org # 5.10+ (needs adjustment for 5.4)
> Signed-off-by: André Draszik <andre.draszik@...aro.org>
> ---
> Changes in v2:
> - change mask definitions to be consistent with other masks (Thinh)
> - udpate commit message to clarify that in some cases the reset value
>   is != 0
> - Link to v1: https://urldefense.com/v3/__https://lore.kernel.org/r/20241206-dwc3-nyet-fix-v1-1-293bc74f644f@linaro.org__;!!A4F2R9G_pg!exwT5XPAys9S8l6RyyVaky6AnKD2swNq-bjYs5za6qQvktfSS812CHZGh-U6oPOu1rIuJ-tPe9TWIEsIHYnbbOmsRfr7$ 
> ---
> For stable-5.4, the if() test is slightly different, so a separate
> patch will be sent for it for the patch to apply.
> ---
>  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..f11570c8ffd0 100644
> --- a/drivers/usb/dwc3/core.h
> +++ b/drivers/usb/dwc3/core.h
> @@ -464,6 +464,7 @@
>  #define DWC3_DCTL_TRGTULST_SS_INACT	(DWC3_DCTL_TRGTULST(6))
>  
>  /* These apply for core versions 1.94a and later */
> +#define DWC3_DCTL_NYET_THRES_MASK	(0xf << 20)
>  #define DWC3_DCTL_NYET_THRES(n)		(((n) & 0xf) << 20)
>  
>  #define DWC3_DCTL_KEEP_CONNECT		BIT(19)
> 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>
> 

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

Thanks,
Thinh