linux-kernel - Re: [PATCH] usb: cdns3: fix incorrect handling TRB

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Message-ID: <20220829015741.GA32096@nchen-desktop>
Date:   Mon, 29 Aug 2022 09:57:41 +0800
From:   Peter Chen <peter.chen@...nel.org>
To:     Pawel Laszczak <pawell@...ence.com>
Cc:     linux-usb@...r.kernel.org, gregkh@...uxfoundation.org,
        felipe.balbi@...ux.intel.com, rogerq@...nel.org,
        a-govindraju@...com, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] usb: cdns3: fix incorrect handling TRB_SMM flag for ISOC
 transfer

On 22-08-25 08:22:07, Pawel Laszczak wrote:
> The TRB_SMM flag indicates that DMA has completed the TD service with
> this TRB. Usually it’s a last TRB in TD. In case of ISOC transfer for
> bInterval > 1 each ISOC transfer contains more than one TD associated
> with usb request (one TD per ITP). In such case the TRB_SMM flag will
> be set in every TD and driver will recognize the end of transfer after
> processing the first TD with TRB_SMM. In result driver stops updating
> request->actual and returns incorrect actual length.
> To fix this issue driver additionally must check TRB_CHAIN which is not
> used for isochronous transfers.
> 
> Fixes: 249f0a25e8be ("usb: cdns3: gadget: handle sg list use case at completion correctly")
> cc: <stable@...r.kernel.org>
> Signed-off-by: Pawel Laszczak <pawell@...ence.com>

Acked-by: Peter Chen <peter.chen@...nel.org>

> ---
>  drivers/usb/cdns3/cdns3-gadget.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/cdns3/cdns3-gadget.c b/drivers/usb/cdns3/cdns3-gadget.c
> index fa8263951e63..a6618a922c61 100644
> --- a/drivers/usb/cdns3/cdns3-gadget.c
> +++ b/drivers/usb/cdns3/cdns3-gadget.c
> @@ -1529,7 +1529,8 @@ static void cdns3_transfer_completed(struct cdns3_device *priv_dev,
>  						TRB_LEN(le32_to_cpu(trb->length));
>  
>  				if (priv_req->num_of_trb > 1 &&
> -					le32_to_cpu(trb->control) & TRB_SMM)
> +					le32_to_cpu(trb->control) & TRB_SMM &&
> +					le32_to_cpu(trb->control) & TRB_CHAIN)
>  					transfer_end = true;
>  
>  				cdns3_ep_inc_deq(priv_ep);
> -- 
> 2.25.1
> 

-- 

Thanks,
Peter Chen