linux-kernel - Re: [PATCH 3/4] usb: remove OMAP USB Device Controller and OHCI support for OMAP1/2 chips

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Message-Id: <179739a0-5d75-412b-964b-16d5cb6d306d@app.fastmail.com>
Date:   Thu, 12 Jan 2023 15:31:20 +0100
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Aaro Koskinen" <aaro.koskinen@....fi>
Cc:     "Tony Lindgren" <tony@...mide.com>,
        "Lukas Bulwahn" <lukas.bulwahn@...il.com>,
        "Janusz Krzysztofik" <jmkrzyszt@...il.com>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski@...aro.org>,
        linux-arm-kernel@...ts.infradead.org,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        linux-usb@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] usb: remove OMAP USB Device Controller and OHCI support for
 OMAP1/2 chips

On Thu, Jan 12, 2023, at 15:05, Aaro Koskinen wrote:
> On Thu, Jan 12, 2023 at 11:19:53AM +0100, Arnd Bergmann wrote:
>> On Thu, Jan 12, 2023, at 10:53, Tony Lindgren wrote:
>> 
>> So if we want to kill off the old DMA stuff there is actually
>> a choice between either making omap_udc PIO-only or converting
>> it to use the standard dmaengine interface.
>
> I use this driver on Palm TE and 770, and without it those boards would
> be useless for my use cases. Also DMA doubles the throughput, probably
> also power usage is smaller.

Ok, if the performance is important, converting to dmaengine
is probably best. Do you know if this is just a straightforward
replacement of the function calls, or are there technical reasons
why it's not using the dmaengine interface yet?

     Arnd