linux-kernel - Re: [RFC 3/4] ARM: imx: add the platform related rpmsg implementation

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Message-ID: <20160215061009.GU6756@tiger>
Date:	Mon, 15 Feb 2016 14:10:09 +0800
From:	Shawn Guo <shawnguo@...nel.org>
To:	Richard Zhu <hongxing.zhu@....com>
Cc:	"ohad@...ery.com" <ohad@...ery.com>,
	Stefan Agner <stefan@...er.ch>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC 3/4] ARM: imx: add the platform related rpmsg implementation

+LAKML

On Thu, Jan 28, 2016 at 02:17:21AM +0000, Richard Zhu wrote:
> Hi Shawn:
> Thanks for your comments.
> Further review would copied to Stefan Agner.

Please do not top-posting.

> On Wed, Jan 06, 2016 at 04:06:43PM +0800, Richard Zhu wrote:
> > From: Richard Zhu <Richard.Zhu@...escale.com>
> > 
> > - add mu driver support, the irq and 4bytes msg of the mu module are 
> > as the interaction channel between A# core and the M4 core on imx amp 
> > platforms.
> > - register one notify in isr of the mu's irq used by rpmsg.
> > - instance the virtual processor, and fill up the virtio_config_ops in 
> > the platform related rpmsg implementation codes.
> > - hard-code the vring storage shared by A# core and M# core on AMP 
> > SOCs.
> > 
> > Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> > ---
> >  arch/arm/mach-imx/Kconfig     |  12 ++
> >  arch/arm/mach-imx/Makefile    |   2 +
> >  arch/arm/mach-imx/imx_rpmsg.c | 364 ++++++++++++++++++++++++++++++++++++++++++
> >  arch/arm/mach-imx/mu.c        | 217 +++++++++++++++++++++++++
> 
> I'm not rpmsg expert, but it seems to me that the driver should be put into drivers/rpmsg/ rather than mach-imx.
> [Richard] This part rpmsg codes are closed related to the platform. For example, kinds of ops callback functions.
> Thus, these codes are placed into arch/arm/mach-imx/ folder. BTW,  so does to omap rpmsg implementation.
> http://omappedia.org/wiki/RPMsg_Kernel_Sources

I just took a closer look at this.  What the omappedia page above
describes is an OMAP rpmsg implementation in a vendor tree which is
in turn based on a relatively old kernel version, i.e. v3.0.

I guess the implementation is a base of what mainline has today on
remoteproc/rpmsg support, but they are somehow different.  For example,
on mainline kernel today, there is no remoteproc/rpmsg code in
arch/arm/plat-omap.  And, instead of handling rpmsg with a platform
specific driver, remoteproc encapsulates the rpmsg support.  You can
find the details in commit ac8954a41393 (remoteproc: create rpmsg virtio
device).

I suggest you look at the mainline code today instead of any old
implementation for reference.  And in any case, with device tree
support to populate platform device as needed, it's a wrong to put
remoteproc/rpmsg related driver code into arch/arm/mach-imx.

Shawn