From: Feng Tang <feng.tang@intel.com>
To: David Brownell <david-b@pacbell.net>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Greg KH <greg@kroah.com>,
spi-devel-list <spi-devel-general@lists.sourceforge.net>,
"linux-serial@vger.kernel.org" <linux-serial@vger.kernel.org>,
Grant Likely <grant.likely@secretlab.ca>,
"alan@lxorguk.ukuu.org.uk" <alan@lxorguk.ukuu.org.uk>
Subject: Re: [PATCH v5] serial: spi: add spi-uart driver for Maxim 3110
Date: Wed, 3 Mar 2010 13:52:05 +0800 [thread overview]
Message-ID: <20100303135205.4fc277c5@feng-i7> (raw)
In-Reply-To: <201003022051.58688.david-b@pacbell.net>
On Wed, 3 Mar 2010 12:51:58 +0800
David Brownell <david-b@pacbell.net> wrote:
> On Tuesday 02 March 2010, Feng Tang wrote:
> > + * 3. This driver doesn't support work with a spi cotnroller in
> > DMA mode,
>
> As Grant said: That's a bug ... one that will randomly
> kick in based on whether the underlying SPI controller driver
> happens to use DMA for a given transaction.
>
>
>From this perspective, yes, it's a bug that this driver use non DMA-safe
IO buffer, which prevents it to be portable for all kinds of controllers,
and I can make it DMA safe.
But I still don't think it's a good idea to use DMA for Max3110 for
performance reason, I know there is some spi controller who only works in
DMA mode.
Here comes another idea, can we add a capability flag in struct spi_master
indicating the master supporting poll or dma or both. Also we add similar
bits in struct spi_transfer indicating the this transfer wants to be handled
in poll or dma mode. For spi controller driver, it can claim its
capability when registering as a spi_master, for a spi device driver, it can
select the working mode based on spi_master's capability and set the working
mode in struct spi_transfer. Then controller and device don't need to guess
what the other is capable, and make the info public. Any thoughts?
Thanks,
Feng
next prev parent reply other threads:[~2010-03-03 5:52 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20091229222006.1ddb28a4@feng-desktop>
2009-12-29 14:59 ` [spi-devel-general] [RFC][PATCH] serial: spi: add spi-uart driver for Maxim 3110 Baruch Siach
2009-12-29 16:05 ` Tang, Feng
2009-12-29 18:43 ` Erwin Authried
2009-12-30 1:54 ` Feng Tang
2010-02-25 4:47 ` David Brownell
2010-02-25 7:49 ` Feng Tang
2009-12-29 15:02 ` Alan Cox
2010-02-08 8:59 ` [RFC][PATCH v2] " Feng Tang
[not found] ` <20100208165946.0e4dde83@feng-i7>
2010-02-09 0:20 ` Andrew Morton
2010-02-09 0:26 ` Grant Likely
2010-02-09 1:36 ` Feng Tang
2010-02-17 22:58 ` Greg KH
2010-02-24 5:11 ` [RFC][PATCH v3] " Feng Tang
2010-02-24 10:44 ` Alan Cox
2010-02-24 14:25 ` Grant Likely
2010-02-24 23:18 ` Andrew Morton
2010-02-25 6:39 ` Feng Tang
2010-02-25 4:43 ` David Brownell
2010-02-25 7:44 ` Feng Tang
2010-02-25 8:11 ` David Brownell
2010-02-26 3:47 ` [PATCH v4] " Feng Tang
[not found] ` <20100226114729.679bb933@feng-i7>
2010-02-26 9:59 ` Masakazu Mokuno
2010-02-26 19:41 ` David Brownell
2010-03-01 2:30 ` Feng Tang
2010-03-02 3:38 ` Feng Tang
2010-02-09 9:25 ` [RFC][PATCH v2] " Alan Cox
2010-03-03 2:57 ` [PATCH v5] " Feng Tang
2010-03-03 3:59 ` Grant Likely
2010-03-03 4:51 ` David Brownell
2010-03-03 5:52 ` Feng Tang [this message]
2010-03-03 6:16 ` David Brownell
2010-03-03 6:37 ` Feng Tang
2010-03-03 7:25 ` David Brownell
2010-03-03 7:42 ` Feng Tang
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