linux-kernel - Re: [PATCH] usb: xhci: bInterval quirk for TI TUSB73x0

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Message-ID: <235e20da-ad1c-d417-02e8-962eaf657d1d@cogentembedded.com>
Date:   Thu, 9 Mar 2017 12:44:33 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Roger Quadros <rogerq@...com>, mathias.nyman@...el.com
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: xhci: bInterval quirk for TI TUSB73x0

Hello!

On 3/9/2017 11:47 AM, Roger Quadros wrote:

> As per [1] issue #4,
> "The periodic EP scheduler always tries to schedule the EPs
> that have large intervals (interval equal to or greater than
> 128 microframes) into different microframes. So it maintains
> an internal counter and increments for each large interval
> EP added. When the counter is greater than 128, the scheduler
> rejects the new EP. So when the hub re-enumerated 128 times,
> it trigged this condition."

    Triggered.

> This results in Bandwidth error when devices with periodic
> endpoints (ISO/INT) having bInterval > 7 are plugged an
> unplugged several times on a TUSB73x0 xhci host.
>
> Workaround this issue by limiting the bInterval to 7
> (i.e. interval to 6) for High-speed or faster periodic endpoints.
>
> [1] - http://www.ti.com/lit/er/sllz076/sllz076.pdf
>
> Signed-off-by: Roger Quadros <rogerq@...com>
[...]

MBR, Sergei