Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20200226210414.28133-1-linux@roeck-us.net> <20200226210414.28133-2-linux@roeck-us.net>
 <CAD=FV=WDd4E-zDW73kb-qHo1QYQrD3BTgVpE70rzowpgeXVy7w@mail.gmail.com>
 <ce3357a1-467f-1241-ae0d-2e113116ca8d@roeck-us.net> <f94fc372-d81b-e8e4-e7ef-780fe7db1237@roeck-us.net>
 <CAD=FV=VNsOo--1x+pkwhWOWSGAQyVB6g6CE+o4q7phPSXaDXRw@mail.gmail.com>
 <20200228175905.GB3188@roeck-us.net> <CAKv9HNbugeO0E5w8PsN-EpgHBtAjOYZppkUz1u0a5Ue6k20GwQ@mail.gmail.com>
 <62d81632-4a6f-b2d8-e420-b58fb6c9d044@roeck-us.net>
In-Reply-To: <62d81632-4a6f-b2d8-e420-b58fb6c9d044@roeck-us.net>
From:   =?UTF-8?B?QW50dGkgU2VwcMOkbMOk?= <a.seppala@gmail.com>
Date:   Sat, 29 Feb 2020 18:33:36 +0200
Message-ID: <CAKv9HNax9bK-60Gkv3ovZDAS_xVEQa95-J_9WKoEkifqa0u9+A@mail.gmail.com>
Subject: Re: [RFT PATCH 1/4] usb: dwc2: Simplify and fix DMA alignment code
To:     Guenter Roeck <linux@roeck-us.net>
Cc:     Doug Anderson <dianders@chromium.org>,
        Minas Harutyunyan <hminas@synopsys.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Boris ARZUR <boris@konbu.org>, linux-usb@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Felipe Balbi <balbi@kernel.org>,
        Stefan Wahren <stefan.wahren@i2se.com>,
        Martin Schiller <ms@dev.tdt.de>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Sat, 29 Feb 2020 at 17:25, Guenter Roeck <linux@roeck-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