-----Original Message-----
From: Sascha Hauer [mailto:s.hauer at pengutronix.de]
Sent: Friday, June 22, 2018 1:50 PM
To: A.s. Dong <aisheng.dong@nxp.com>
Cc: Rob Herring <robh@kernel.org>; linux-arm-kernel at lists.infradead.org;
dongas86 at gmail.com; kernel at pengutronix.de; shawnguo at kernel.org;
Fabio Estevam [off-list ref]; dl-linux-imx <linux-
imx at nxp.com>; Mark Rutland [off-list ref];
devicetree at vger.kernel.org
Subject: Re: [PATCH V2 2/4] dt-bindings: arm: fsl: add mu binding doc

On Thu, Jun 21, 2018 at 05:11:33PM +0000, A.s. Dong wrote:

quoted

Hi Sascha,

quoted

-----Original Message-----
From: Sascha Hauer [mailto:s.hauer at pengutronix.de]
Sent: Thursday, June 21, 2018 3:47 PM
To: Rob Herring <robh@kernel.org>
Cc: A.s. Dong <aisheng.dong@nxp.com>; linux-arm-
kernel at lists.infradead.org; dongas86 at gmail.com;
kernel at pengutronix.de; shawnguo at kernel.org; Fabio Estevam
[off-list ref]; dl-linux- imx [off-list ref]; Mark
Rutland [off-list ref]; devicetree at vger.kernel.org
Subject: Re: [PATCH V2 2/4] dt-bindings: arm: fsl: add mu binding
doc

On Wed, Jun 20, 2018 at 01:43:10PM -0600, Rob Herring wrote:

quoted

On Sun, Jun 17, 2018 at 08:49:47PM +0800, Dong Aisheng wrote:

quoted

The Messaging Unit module enables two processors within the SoC
to communicate and coordinate by passing messages (e.g. data,
status and control) through the MU interface.

Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: Fabio Estevam <redacted>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: devicetree at vger.kernel.org
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
---
v1->v2:
 * typo fixes
 * remove status property
 * remove imx6&7 compatible string which may be added later for
   the generic mailbox binding

Note: Because MU used by SCU is not implemented as a mailbox
driver, Instead, they're provided in library calls to gain higher

performance.

quoted

quoted

quoted

Using a binding doesn't mean you have to use an OS's subsystem.

What needs higher performance? What's the performance difference?

Why

quoted

can't the mailbox framework be improved?

From what I see the performance is improved by polling the interrupt
registers rather than using interrupts.
I see no reason though why this can't be implemented with the
mailbox framework as is.

I thought you've agreed to not write generic MU(mailbox) driver for SCU.

https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fw
ww

quoted

.spinics.net%2Flists%2Farm-

kernel%2Fmsg650217.html&data=02%7C01%7Caish

quoted

eng.dong%40nxp.com%7Cfb1c9e5d6eff453207a908d5d803f139%7C686ea1d3
bc2b4c

quoted

6fa92cd99c5c301635%7C0%7C0%7C636652433808619368&sdata=vOFbr%2BSJ
1tkY5F

quoted

8ha1wrxk3RMVxI4lzKkidD9cK%2Bl9A%3D&reserved=0
But seems it's still not quite certain...

My suggestion was that we change the compatible of the MU unit to
something that the SCU driver matches. But since we do not do that and
instead use a fsl,imx8qxp-mu compatible for the MU we have to come up
with a MU driver that handles both the SCU case and the regular usecase.
Otherwise we'll end up with a generic driver attaching to the device you are
using under the hoods.

Do you think checking mbox-cells can work?
E.g. SCU MU mbox-cells should be 0 while general purpose MU are 1.

Regards
Dong Aisheng

Sascha

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