From: Matthieu CASTET <matthieu.castet-ITF29qwbsa/QT0dZR+AlfA@public.gmane.org>
To: "Patra, Nilkesh" <nilkesh.patra-l0cyMroinI0@public.gmane.org>
Cc: "linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
David Brownell <david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>,
"Gadiyar, Anand" <gadiyar-l0cyMroinI0@public.gmane.org>
Subject: Re: [RFC] MUSB: Workaround for Ethernet data alignment issue
Date: Tue, 15 Dec 2009 11:28:11 +0100 [thread overview]
Message-ID: <4B2764BB.3010306@parrot.com> (raw)
In-Reply-To: <4B276145.1080909-ITF29qwbsa/QT0dZR+AlfA@public.gmane.org>
Matthieu CASTET a écrit :
> Hi,
>
> Patra, Nilkesh a écrit :
>> On the latest version of MUSB, DMA is not working properly if the Data in the packet doesn't start at 32bit aligned address. This issue was found while using MUSB as g_ether. The basic ping does not work, if the data in the Ethernet packet does not start at 32bit aligned address.
>>
>> To overcome this issue, we found one solution mentioned in the below patch. This patch moves data (skb->data) by 2 bytes backwards in ethernet packet, which is nothing but skb->head.
>>
>> I want to know, if there are any better approaches to fix this issue.
>>
> What dma_mask are you using ?
>
>>From what I understand, dma_map_single will use it to know if the dma
> buffer need to be aligned [1].
> So you need to set the last 2 bits to 0 and it should do everything for you.
>
Forget what I said it is only true in CONFIG_DMABOUNCE case...
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prev parent reply other threads:[~2009-12-15 10:28 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-14 4:50 [RFC] MUSB: Workaround for Ethernet data alignment issue Patra, Nilkesh
[not found] ` <B85A65D85D7EB246BE421B3FB0FBB59301DEAB8723-/tLxBxkBPtCIQmiDNMet8wC/G2K4zDHf@public.gmane.org>
2009-12-14 17:39 ` Pandita, Vikram
2009-12-14 20:30 ` Sonasath, Moiz
2009-12-16 7:11 ` Patra, Nilkesh
2009-12-15 10:13 ` Matthieu CASTET
[not found] ` <4B276145.1080909-ITF29qwbsa/QT0dZR+AlfA@public.gmane.org>
2009-12-15 10:28 ` Matthieu CASTET [this message]
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