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

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Message-ID: <1d4406de-c428-a2b2-55b2-5e68d21aab3a@ti.com>
Date:   Fri, 10 Mar 2017 18:04:27 +0200
From:   Roger Quadros <rogerq@...com>
To:     Sergei Shtylyov <sergei.shtylyov@...entembedded.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

On 09/03/17 11:44, Sergei Shtylyov wrote:
> 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.

Should be "triggers" actually.
Will fix it. Thanks.

> 
>> 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
> 

-- 
cheers,
-roger