linux-kernel - Re: [PATCH v2] usb: xhci: quirk for data loss in ISOC transfers

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Message-ID: <2024111226-spender-saturate-dc6e@gregkh>
Date: Tue, 12 Nov 2024 13:24:53 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Raju Rangoju <Raju.Rangoju@....com>
Cc: linux-usb@...r.kernel.org, mathias.nyman@...el.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] usb: xhci: quirk for data loss in ISOC transfers

On Tue, Nov 12, 2024 at 05:51:04PM +0530, Raju Rangoju wrote:
> During the High-Speed Isochronous Audio transfers, xHCI
> controller on certain AMD platforms experiences momentary data
> loss. This results in Missed Service Errors (MSE) being
> generated by the xHCI.
> 
> The root cause of the MSE is attributed to the ISOC OUT endpoint
> being omitted from scheduling. This can happen either when an IN
> endpoint with a 64ms service interval is pre-scheduled prior to
> the ISOC OUT endpoint or when the interval of the ISOC OUT
> endpoint is shorter than that of the IN endpoint. Consequently,
> the OUT service is neglected when an IN endpoint with a service
> interval exceeding 32ms is scheduled concurrently (every 64ms in
> this scenario).
> 
> This issue is particularly seen on certain older AMD platforms.
> To mitigate this problem, it is recommended to adjust the service
> interval of the IN endpoint to not exceed 32ms (interval 8). This
> adjustment ensures that the OUT endpoint will not be bypassed,
> even if a smaller interval value is utilized.
> 
> Signed-off-by: Raju Rangoju <Raju.Rangoju@....com>

You don't want this backported to any older kernels?  Why not?

thanks,

greg k-h