linux-kernel - Re: [PATCH] usb: host: xhci-plat: Enable XHCI_SPURIOUS

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Date:	Wed, 26 Jun 2013 12:02:13 +0300
From:	Felipe Balbi <balbi@...com>
To:	George Cherian <george.cherian@...com>
CC:	<linux-usb@...r.kernel.org>, <balbi@...com>,
	<linux-kernel@...r.kernel.org>, <gregkh@...uxfoundation.org>,
	<sarah.a.sharp@...ux.intel.com>
Subject: Re: [PATCH] usb: host: xhci-plat: Enable XHCI_SPURIOUS_SUCCESS quirk
 for xhci-plat

Hi,

On Wed, Jun 26, 2013 at 02:28:57PM +0530, George Cherian wrote:
> Synopsis xhci controllers with hci_version > 0.96 gives spurious success
> events on short packet completion. During webcam capture the
> "ERROR Transfer event TRB DMA ptr not part of current TD" was observed.
> The same application works fine with synopsis controllers hci_version 0.96.
> 
> Signed-off-by: George Cherian <george.cherian@...com>
> ---
>  drivers/usb/host/xhci-plat.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
> index 93ad67e..e63c6d3 100644
> --- a/drivers/usb/host/xhci-plat.c
> +++ b/drivers/usb/host/xhci-plat.c
> @@ -25,6 +25,16 @@ static void xhci_plat_quirks(struct device *dev, struct xhci_hcd *xhci)
>  	 * dev struct in order to setup MSI
>  	 */
>  	xhci->quirks |= XHCI_BROKEN_MSI;
> +
> +	/*
> +	 * In some xhci controllers which follows xhci 1.0 spec gives a spurious
> +	 * success event after a short transfer. This quirk will ignore such
> +	 * spurious event. Hit this issue in synopsis xhci controllers with
> +	 * hci_version > 0.96
> +	 */
> +
> +	if (xhci->hci_version > 0x96)
> +		xhci->quirks |= XHCI_SPURIOUS_SUCCESS;
>  }

doesn't look like the correct way to do this. What if enabling that
quirk on hosts which don't have the quirk cause problems ?

I would suggest adding a platform_data which (in our case) dwc3 will
pass to xhci-plat. Then you can do proper revision detection of the
synopsys controller and set the quirk only on the failing hosts.

BTW, do you have the STARS number for this errata ?

-- 
balbi

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