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Date: Wed, 12 Oct 2011 17:48:11 +0400
From: Sergei Shtylyov <sshtylyov@ru.mvista.com>
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To: Markus Rechberger <mrechberger@gmail.com>
CC: Greg KH <gregkh@suse.de>, Alan Stern <stern@rowland.harvard.edu>,
        USB list <linux-usb@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [Patch] Increase USBFS Bulk Transfer size
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On 10/12/2011 04:36 PM, Markus Rechberger wrote:

> We have 2 products which can perform better with increased Bulk transfers

> Device No. 1:
> According to the hardware spec of on of our product
> Available Bulk Transfer Size are:
> - 188 * n bytes, where n = 1 ~ 256.

> Although we can drive that one with 15K as well when setting the HW
> register down to it.

> Device No. 2
> only creates jitter video with Bulk transfer sizes which are below
> 24064 bytes, no such chipfeature is available
> to decrease the bulk transfer size.
> http://sundtek.de/images/dtvjitter2.jpg
> with transfer size of 24064:
> http://sundtek.de/images/gooddata.jpg

> The patch takes the features of Device No. 1 into account allowing a
> maximum buffer of 48128 bytes.

> Those issues have been evaluated with MacOSX and a customized patched
> Linux version.
> Device No. 2 also corrupts on MacOSX with too small packet sizes,
> Windows and Mac are using 24064 bytes.

    You are constantly mixing the packet size and the transfer size.

> Default Bulk Transfersize of device No. 1 is around 1-2k which leads
> to very high cpu usage, updating it to 15k lowers that one.

WBR, Sergei