linux-kernel - Re: Could I (ab)use bus (struct bus

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Message-ID: <BANLkTim6iCAsViJQS4XrY-XObs8pp-BiQQ@mail.gmail.com>
Date:	Mon, 18 Apr 2011 14:19:38 +0200
From:	Rafał Miłecki <zajec5@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	George Kashperko <george@...u.edu.ua>,
	Hauke Mehrtens <hauke@...ke-m.de>,
	Russell King <rmk@....linux.org.uk>,
	linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Arend van Spriel <arend@...adcom.com>,
	Jonas Gorski <jonas.gorski@...il.com>,
	b43-dev@...ts.infradead.org, Greg KH <greg@...ah.com>,
	Andy Botting <andy@...ybotting.com>,
	Larry Finger <Larry.Finger@...inger.net>
Subject: Re: Could I (ab)use bus (struct bus_type) for virtual Broadcom bus?

W dniu 17 kwietnia 2011 19:38 użytkownik Arnd Bergmann <arnd@...db.de> napisał:
> On Friday 15 April 2011, Rafał Miłecki wrote:
>> W dniu 15 kwietnia 2011 20:36 użytkownik George Kashperko
>> <george@...u.edu.ua> napisał:
>> >> >> Arnd: I found you saying:
>> >> >> > I believe the one thing we really want from this driver is the bus
>> >> >> > scan code, which is not present in the amba bus implementation,
>> >> >> I explained how it works, I believe scanning (EPROM in this case) it
>> >> >> Broadcom specific, not really AMBA standard. How do you see it?
>> >>
>> >> Maybe EPROM is not Broadcom specific, but I suspect the content we
>> >> deal with in bcmai/axi is Broadcom specific. I didn't see any notes of
>> >> manuf/id/rev/class we deal with. So I guess everything we (out
>> >> driver) read from EPROM is Bcm specific.
>> >>
>> >
>> > Played around amba registers on bcm4716. For all amba cores present
>> > (under all I mean broadcom ip core agents, oob router core, erom core,
>> > and other I-dont-know-what-for cores present at 0x18100000). All those
>> > feature AMBA_CID (0xb105f00d) as PrimeCell ID, and slightly different
>> > PrimeCell PeripheralIDs:
>> > * vendor 0xBB, part_number 0x368 for broadcom cores' agents;
>> > * vendor 0xBB, part_number 0x367 for OOB router core (don't ask me wth
>> > is this please);
>> > * vendor 0xBB, part_number 0x366 for EROM core;
>> >
>> > ARM vendor id is 0x41. Might 0xBB is Broadcom vendor id but I've found
>> > no evidence for that with google.
>>
>> Yeah, as I suspected, everything except Broadcom specific cores
>> matches AMBA standards quite nicely. Still, I don't see anything in it
>> we could use for driver.
>>
>> Let's wait for Russell and Arnd to comment.
>
> In general, the bus_type directly relates to how a device gets probed.
> If broadcom uses the same basic register layout as regular AMBA devices,
> it should use the amba bus type.

>From Broadcom side we *could* use some registers that are AMBA
specific, they are present... but there is totally no point in doing
that. Everything we use is Broadcom specific.


> I think it would be fine to extend the AMBA bus slightly if there are
> just minor differences.

As I said, Broadcom specific driver use nothing from AMBA common
things. Plus we implement routines that are Broadcom specific and no
other platform will use them.

-- 
Rafał
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