From: Oliver Neukum <oneukum@suse.de>
To: David Miller <davem@davemloft.net>
Cc: hayeswang@realtek.com, gregkh@linuxfoundation.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-usb@vger.kernel.org
Subject: Re: [PATCH v2 1/3] net/usb/r815x: replace USB buffer from stack to DMA-able
Date: Mon, 29 Jul 2013 07:20:24 +0200 [thread overview]
Message-ID: <1375075224.25230.1.camel@linux-fkkt.site> (raw)
In-Reply-To: <20130727.202107.555068116238400560.davem@davemloft.net>
On Sat, 2013-07-27 at 20:21 -0700, David Miller wrote:
> From: Hayes Wang <hayeswang@realtek.com>
> Date: Thu, 25 Jul 2013 15:59:02 +0800
>
> > Some USB buffers use stack which may not be DMA-able.
> > Use the buffers from kmalloc to replace those one.
> >
> > Signed-off-by: Hayes Wang <hayeswang@realtek.com>
>
> I don't think it's reasonable to kmalloc() a small integer every time
> you want to use a USB message transfer to read or write chip
> registers.
>
> Instead, add a scratch buffer to struct r8152 which is allocated once
> at driver attach time and which you can use for the transfers.
>
> I think you only need an array of two u32's so something like:
>
> u32 transfer_buf[2];
>
> ought to be sufficient.
We cannot do that. It would violate the rules about DMA coherency.
We must not touch the same cacheline while DMA is in operation.
Regards
Oliver
next prev parent reply other threads:[~2013-07-29 5:20 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-23 9:26 [PATCH 1/3] net/usb/r815x: replace USB buffer from stack to DMA-able hayeswang
2013-07-25 0:49 ` David Miller
2013-07-25 7:59 ` [PATCH v2 " Hayes Wang
2013-07-25 7:59 ` [PATCH v2 2/3] net/usb/r8152: make sure the USB buffer is DMA-able Hayes Wang
2013-07-25 7:59 ` [PATCH v2 3/3] net/usb/r8152: adjust relative ocp function Hayes Wang
[not found] ` <1374739144-732-1-git-send-email-hayeswang-Rasf1IRRPZFBDgjK7y7TUQ@public.gmane.org>
2013-07-28 3:21 ` [PATCH v2 1/3] net/usb/r815x: replace USB buffer from stack to DMA-able David Miller
2013-07-29 5:20 ` Oliver Neukum [this message]
2013-07-29 7:46 ` David Miller
2013-07-30 8:28 ` [PATCH v3 " Hayes Wang
2013-07-30 8:28 ` [PATCH v3 2/3] net/usb/r8152: " Hayes Wang
2013-07-30 14:01 ` Greg KH
2013-07-30 8:28 ` [PATCH v3 3/3] net/usb/r8152: adjust relative ocp function Hayes Wang
2013-07-30 13:58 ` [PATCH v3 1/3] net/usb/r815x: replace USB buffer from stack to DMA-able Greg KH
2013-07-30 15:17 ` [PATCH] MAINTAINERS: USB, remove F: drivers/net/usb/ pattern Joe Perches
2013-07-30 14:00 ` [PATCH v3 1/3] net/usb/r815x: replace USB buffer from stack to DMA-able Greg KH
2013-07-30 18:33 ` David Miller
2013-07-30 18:41 ` Joe Perches
2013-07-30 18:49 ` David Miller
2013-07-31 10:29 ` Ming Lei
2013-07-30 18:58 ` Greg KH
2013-07-30 14:29 ` Ming Lei
2013-07-31 9:21 ` [PATCH v4 1/5] " Hayes Wang
2013-07-31 9:21 ` [PATCH v4 2/5] net/usb/r815x: avoid to call mdio functions for runtime-suspended device Hayes Wang
2013-07-31 21:49 ` David Miller
2013-07-31 9:21 ` [PATCH v4 3/5] net/usb/r815x: change the return value for bind functions Hayes Wang
[not found] ` <1375262486-5373-3-git-send-email-hayeswang-Rasf1IRRPZFBDgjK7y7TUQ@public.gmane.org>
2013-07-31 21:49 ` David Miller
[not found] ` <1375262486-5373-1-git-send-email-hayeswang-Rasf1IRRPZFBDgjK7y7TUQ@public.gmane.org>
2013-07-31 9:21 ` [PATCH v4 4/5] net/usb/r8152: make sure the USB buffer is DMA-able Hayes Wang
2013-07-31 12:54 ` Greg KH
2013-07-31 21:50 ` David Miller
2013-07-31 9:21 ` [PATCH v4 5/5] net/usb/r8152: adjust relative ocp function Hayes Wang
2013-07-31 21:50 ` David Miller
2013-07-31 12:53 ` [PATCH v4 1/5] net/usb/r815x: replace USB buffer from stack to DMA-able Greg KH
2013-07-31 21:49 ` David Miller
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