linux-kernel - Re: [PATCH v4 01/11] mfd: add pruss mfd driver.

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Date:	Wed, 27 Apr 2011 19:08:03 +0530
From:	"Subhasish Ghosh" <subhasish@...tralsolutions.com>
To:	"Arnd Bergmann" <arnd@...db.de>,
	<linux-arm-kernel@...ts.infradead.org>
Cc:	<davinci-linux-open-source@...ux.davincidsp.com>,
	<sachi@...tralsolutions.com>,
	"Samuel Ortiz" <sameo@...ux.intel.com>, <nsekhar@...com>,
	"open list" <linux-kernel@...r.kernel.org>, <m-watkins@...com>
Subject: Re: [PATCH v4 01/11] mfd: add pruss mfd driver.

PRU's resulting in improved load sharing.
>>
>> Signed-off-by: Subhasish Ghosh <subhasish@...tralsolutions.com>
>
> Hi Subhasish,
>
> This looks like great progress since the last time I looked at the
> pruss mfd driver, good work there!
>
> Thanks to your explanations and the documentation link, I now have
> a better understanding of what is actually going on here, but I'd
> still like to understandhow the decision is made regarding what programs
> are loaded into each PRU and how the MFD cells are set up.

>
> Is this a fixed setting for each board that strictly depends on how
> the external pins are connected, or is it possible to use the same
> hardware for different purposes based on the program?

SG  -- The PRU pins are exposed as is on the main board,
            we have separate add on daughter cards
            specific to the protocol implemented on it.

>
> If I read your code correctly, you hardwire the usage of the two
> PRUs in the da850 board code, which makes it impossible to use
> them in different ways even if the hardware supports it. If this is
> indeed the case, using an MFD device might not be the best option
> and we should try to come up with a way to dynamically repurpose
> the PRU with some user interface.

SG -- It depends upon how the firmware is implemented. If another
            firmware is downloaded on it, it will emulate another device.
            Also, if a firmware emulated on it supports switching between 
devices,
            that too is possible. Its just a microcontroller, we can do 
whatever we feel like
            with it. Both the PRUs have separate instruction/data ram, so 
both can be used
            to implement two different devices.
 

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