linux-kernel - Re: remoteproc: Load coprocessor code to the specific main memory location

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Date:	Fri, 17 Feb 2012 02:55:33 +0100
From:	Ohad Ben-Cohen <ohad@...ery.com>
To:	Michal Simek <monstr@...str.eu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	John Williams <john.williams@...alogix.com>,
	linux-arm <linux-arm-kernel@...ts.infradead.org>,
	"Grosen, Mark" <mgrosen@...com>, Arnd Bergmann <arnd@...db.de>,
	Grant Likely <grant.likely@...retlab.ca>,
	devicetree-discuss@...ts.ozlabs.org
Subject: Re: remoteproc: Load coprocessor code to the specific main memory location

On Thu, Feb 16, 2012 at 9:21 PM, Michal Simek <monstr@...str.eu> wrote:
> IRC in init part Linux kick rtos which send which services are available.in
> any format which is unknown to me.

Check out struct rpmsg_ns_msg - that's the exact format of the name
service notification messages (it's also mentioned by
Documentation/rpmsg.txt).

Of course, these messages, like any other message that is sent across,
need to begin with the usual rpmsg header. Its format is defined by
struct rpmsg_hdr.

To send the message from the rtos to Linux, you then need to grab a
buffer from the available ring (of the vring which is used by Linux to
receive messages), fill it with the message, put it in the used ring,
and kick the Linux side.

> Please also correct me if I read the code wrongly. that mailbox in omap
> driver is used just to say which buffer contains that message. Is it
> correct?

We're using the mailbox payload in order to indicate which vring has
pending buffers.

> I can create 15 sw signals to tell rtos which buffer contains message.

You can also just use a single interrupt and then, when it is
triggered, check both vrings for pending buffers. It's just another if
statement and shouldn't be too much of an overhead.

> Will be help if I clear my code and send it to you for review? Maybe you
> will see where the problem is.

I'm not sure I'll have the time to review it, but let's try to
progress this way and see how it goes.

Sorry I couldn't answer faster this week - I'm in ELC and was a bit
away from emails. I'll soon be flying back and that will keep me away
from emails again, but b/o next week I'll be online again.

Thanks,
Ohad.
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