dmaengine: mcf-edma: add ColdFire mcf5441x eDMA support

[Vinod Koul <vinod.koul@linaro.org>]

On Fri, May 04, 2018 at 09:18:19PM +0200, Angelo Dureghello wrote:
> Hi Vinod,
> 
> thanks for the review,
> 
> On Thu, May 03, 2018 at 10:18:30PM +0530, Vinod Koul wrote:
> > On Wed, Apr 25, 2018 at 10:08:17PM +0200, Angelo Dureghello wrote:
> > > This patch adds dma support for NXP mcf5441x (ColdFire) family.
> > > 
> > > ColdFire mcf5441x implements an edma hw module similar to the
> > 
> > Is it similar to to edma ?
> > 
> 
> It is similar to Freescale "edma" but with a different number of
> channels, a bit different register set, different interrupt
> structure, no channel multiplexer.

ok

> > > one implemented in Vybrid VFxxx controllers, but with a slightly
> > > different register set, more dma channels (64 instead of 32),
> > > a different interrupt mechanism and some other minor differences.
> > > 
> > > For the above reasons, modfying fsl-edma.c was too complex and
> > > likely too ugly. From here, the decision to create a different
> > > driver, but starting from fsl-edma.
> > 
> > can the common stuff be made into a lib and shared between then two rather
> > than having a same driver or different drivers?
> 
> It should be possible to collect some common code in a kind of
> mcf_edma_core.c common module, but in this case i cannot then test
> the Vybrid edma after the changes since i miss that hardware.

Sure you should send the patches and folks who care about fsl driver
would look it up and test

> Would be maybe possible for you to diff fsl-edma and this mcf-edma,
> just to confirm if i can still stay this way, or if moving to a
> library becomes mandatory ?

well since you know the IP you would make a better guess on that, best is
to check register sets in drivers

> > > +// SPDX-License-Identifier: GPL-2.0
> > 
> > Copyright info should be here in c99 style comments
> > 
> 
> Seems checkpatch.pl, for C files, does not like the C style
> initial line comment:
> 
> WARNING: Missing or malformed SPDX-License-Identifier tag in line 1
> #87: FILE: drivers/dma/mcf-edma.c:1:
> +/* SPDX-License-Identifier: GPL-2.0 */
> 
> While c++ type is accepted.
> 
> In contrary, in .h files it wants cpp // style and not C style.

SC99 comments style is
// SPDX-License-Identifier: GPL-2.0

Point is the copyright should be added is same formar i.e.,

// Copyright 20018 - foo bar

this line should follow the spdx line

> > > +
> > > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> > 
> > why do you need this, why not use dev_xxx
> >
> 
> Well, pr_ style seems to simplify the call a bit, should be allowed
> but if you prefer i can move all to dev_ format.

in hindsight dev_ makes better sense, been there done that :)