linux-kernel - Re: [RFT PATCH 1/4] usb: dwc2: Simplify and fix DMA alignment code

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Message-ID: <CAKv9HNax9bK-60Gkv3ovZDAS_xVEQa95-J_9WKoEkifqa0u9+A@mail.gmail.com>
Date:   Sat, 29 Feb 2020 18:33:36 +0200
From:   Antti Seppälä <a.seppala@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Doug Anderson <dianders@...omium.org>,
        Minas Harutyunyan <hminas@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Boris ARZUR <boris@...bu.org>, linux-usb@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Felipe Balbi <balbi@...nel.org>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Martin Schiller <ms@....tdt.de>
Subject: Re: [RFT PATCH 1/4] usb: dwc2: Simplify and fix DMA alignment code

On Sat, 29 Feb 2020 at 17:25, Guenter Roeck <linux@...ck-us.net> wrote:
>
> Sigh. It would have been too simple. Too bad I can't test myself.
> I'd like to know if this is because URB_NO_TRANSFER_DMA_MAP is set on a
> transfer, or because the beginning of the buffer indeed needs to be aligned
> to the DMA cache line size on that system. In the latter case, the question
> is why the alignment to DWC2_USB_DMA_ALIGN (=4) works. In the former case,
> question would be why the realignment does any good in the first place.
>
> Any chance you can add some test code to help figuring out what exactly
> goes wrong ?
>

Sure, I can try to help. Just let me know what code you would like to
insert and where and I'll see what I can do.

-- 
Antti