From: Marek Vasut <marex-ynQEQJNshbs@public.gmane.org>
To: Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org,
linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
Fabio Estevam
<fabio.estevam-KZfg59tc24xl57MIdRCFDg@public.gmane.org>,
linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Shawn Guo <shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH V4] MXS: Implement DMA support into mxs-i2c
Date: Sun, 16 Sep 2012 13:14:20 +0200 [thread overview]
Message-ID: <201209161314.21049.marex@denx.de> (raw)
In-Reply-To: <20120916111223.GD933-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
Dear Wolfram Sang,
> > > Unsurprisingly, I also couldn't get the mode switching between DMA and
> > > PIOQUEUE to work :(
> >
> > I'd say more work should be invested into this.
>
> I ran out of ideas. Next thing I'd do is to ask FSL if this is possible
> at all. Yet, I'd like to have some solution for 3.7.
Why? You now have the module option solution.
> > Besides, what about rather > trying PIO + DMA instead of PIOQ + DMA?
>
> That could also be a solution.
>
> > > However, I did come up with an idea how to select DMA or PIOQUEUE per
> > > bus via devicetree. If we change the view from "I want PIOQUEUE" to "I
> > > don't want DMA", we could simply override the default DMA configuration
> > >
> > > in the devicetree with, e.g.:
> > > i2c0: i2c@80058000 {
> > >
> > > ...
> > > fsl,i2c-dma-channel = <>;
> > >
> > > };
> > >
> > > So, no DMA channel set up will fall back to PIOQUEUE. This is more
> > > generic than a custom binding, because if one doesn't want DMA, don't
> > > configure it. That should also work with other devices which can fall
> > > back to something. I think this is worth trying, another advantage is
> > > that it doesn't expose something new to the user. So, there is no
> > > legacy support needed in case there will be a better way of
> > > configuration.
> >
> > Ewww ... that's such an ad-hoc hack.
>
> Please give reasons.
It's abuse of proper configuration of hardware property.
> > Besides, someone might simply forget to add the binding, you'd need to
> > print a warning.
>
> ? It is "on" by default because of the entry in the dtsi. And the status
> of DMA will be printed.
>
> > > + dev_info(dev, "registered. DMA: %s\n", i2c->dma_mode ? "on" : "off");
> >
> > dev_debug() ?
>
> Yup.
Best regards,
Marek Vasut
next prev parent reply other threads:[~2012-09-16 11:14 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-24 3:44 [PATCH V4] MXS: Implement DMA support into mxs-i2c Marek Vasut
[not found] ` <1345779871-7677-1-git-send-email-marex-ynQEQJNshbs@public.gmane.org>
2012-08-27 18:54 ` Fabio Estevam
[not found] ` <CAOMZO5CSvP3nXNq4VLYALh+U9OZRnjtgXqTr7zsKdeHpUdJ4cQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-09-16 10:44 ` Wolfram Sang
[not found] ` <20120916104436.GC933-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2012-09-16 14:44 ` Fabio Estevam
2012-09-16 10:23 ` Wolfram Sang
[not found] ` <20120916102342.GA933-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2012-09-16 10:51 ` Marek Vasut
[not found] ` <201209161251.41895.marex-ynQEQJNshbs@public.gmane.org>
2012-09-16 11:12 ` Wolfram Sang
[not found] ` <20120916111223.GD933-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2012-09-16 11:14 ` Marek Vasut [this message]
2012-09-27 0:03 ` Marek Vasut
2012-10-08 9:25 ` Wolfram Sang
[not found] ` <20121008092530.GA22051-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2012-10-08 13:15 ` Marek Vasut
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