Date:	Fri, 28 Nov 2014 17:07:12 +0000 (UTC)
From:	Paul Walmsley <paul@...an.com>
To:	Rafał Miłecki <zajec5@...il.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
cc:	"linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>,
	Hauke Mehrtens <hauke@...ke-m.de>,
	Kumar Gala <galak@...eaurora.org>,
	Olof Johansson <olof@...om.net>, Arnd Bergmann <arnd@...db.de>,
	Sandeep Nair <sandeep_n@...com>, linux-soc@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3] MIPS: BCM47XX: Move NVRAM driver to the
 drivers/soc/

Hi Rafał,

On Thu, 27 Nov 2014, Rafał Miłecki wrote:

> On 27 November 2014 at 20:56, Paul Walmsley <paul@...an.com> wrote:
> > On Tue, 25 Nov 2014, Rafał Miłecki wrote:
> >> I understand your arguments against drivers/soc/, but on the other hand
> >> I have no idea where else this driver could go.
> >
> > After looking around the tree to find out where similar code is located,
> > it looks like drivers/firmware is the right place.  These days,
> > drivers/firmware is mainly used for drivers that parse EFI bootloader
> > data, DMI data, that sort of thing.  Quite similar to the CFE-provided
> > data that the bcm47xx-nvram code deals with.  So, by functional analogy,
> > drivers/firmware appears to be the right place to stash this device
> > data-probing code.
> >
> >> I guess DT is older than CFE, but Broadcom decided to invent own
> >> solution called NVRAM anyway. This is a bit messy, because it actually
> >> stores hardware details (CPU, RAM, switch) as well as user settings
> >> (e.g. LEDs behavior). I can't say why Broadcom decided to implement it
> >> this way.
> >
> > Yep, based on what the other drivers in drivers/firmware are used for, I
> > think drivers/firmware is the right place for the CFE parsing code.
> 
> The problem is I can't find MAINTAINER of the drivers/firmware/. Is
> there someone responsible for that? Some mailing list maybe? Who could
> give us an ACK to move bcm47xx_nvram there?

The list of folks who have committed patches that touch drivers/firmware 
is large.  I did this as a first-order approximation:

$ git log --format=fuller drivers/firmware/* | grep Commit: | sort -u
Commit:     Adrian Bunk <bunk@...nel.org>
Commit:     Adrian Bunk <bunk@...sta.de>
Commit:     Al Viro <viro@...iv.linux.org.uk>
Commit:     Andi Kleen <andi@...il.nowhere.org>
Commit:     Benjamin Herrenschmidt <benh@...nel.crashing.org>
Commit:     David S. Miller <davem@...emloft.net>
Commit:     David Woodhouse <David.Woodhouse@...el.com>
Commit:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Commit:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Commit:     Greg Kroah-Hartman <gregkh@...e.de>
Commit:     H. Peter Anvin <hpa@...ux.intel.com>
Commit:     H. Peter Anvin <hpa@...or.com>
Commit:     Ingo Molnar <mingo@...e.hu>
Commit:     Ingo Molnar <mingo@...nel.org>
Commit:     James Bottomley <James.Bottomley@...e.de>
Commit:     James Bottomley <JBottomley@...allels.com>
Commit:     Jean Delvare <khali@...ux-fr.org>
Commit:     Jeff Garzik <jeff@...zik.org>
Commit:     Jeff Garzik <jgarzik@...hat.com>
Commit:     Jesse Barnes <jbarnes@...tuousgeek.org>
Commit:     Jiri Kosina <jkosina@...e.cz>
Commit:     Konrad Rzeszutek Wilk <konrad@...nel.org>
Commit:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Commit:     Len Brown <len.brown@...el.com>
Commit:     Linus Torvalds <torvalds@...osdl.org>
Commit:     Linus Torvalds <torvalds@...ux-foundation.org>
Commit:     Linus Torvalds <torvalds@...970.osdl.org>
Commit:     Linus Torvalds <torvalds@...dy.linux-foundation.org>
Commit:     Linus Torvalds <torvalds@...dy.osdl.org>
Commit:     Mark Brown <broonie@...nsource.wolfsonmicro.com>
Commit:     Mark M. Hoffman <mhoffman@...htlink.com>
Commit:     Matt Fleming <matt.fleming@...el.com>
Commit:     Matthew Wilcox <willy@...ux.intel.com>
Commit:     Paul Gortmaker <paul.gortmaker@...driver.com>
Commit:     Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Commit:     Russell King <rmk+kernel@....linux.org.uk>
Commit:     Tejun Heo <tj@...nel.org>
Commit:     Theodore Ts'o <tytso@....edu>
Commit:     Thomas Gleixner <tglx@...utronix.de>
Commit:     Tony Luck <tony.luck@...el.com>

If I were in your shoes, I would suggest either

1. asking Ralf to merge your patches that touch drivers/firmware, since 
he'll also presumably be merging the parts that touch arch/mips

or 

2. asking Greg KH to merge those patches

And of course it would not hurt to collect some Reviewed-By:s from other 
folks.  (See below...)

> >> > It sounds to me like this code is a combination of three
> >> > pieces:
> >> >
> >> > 1. code that autoprobes the size of the "nvram" partition in the Broadcom
> >> > platform flash, by reading various locations in the MMIO flash aperture,
> >> > configured by some other system entity
> >>
> >> That's right, on MIPS we simply detect flash type (drivers/ssb &
> >> driver/bcma) and using that we init NVRAM passing memory offset where
> >> the flash is mapped.
> >
> > OK.
> >
> > So (as a side issue), I would suggest that when you move this code out of
> > arch/mips, the MIPS-isms in it should be removed, like KSEG1ADDR(), etc.,
> > and replaced by the standard ioremap()-type approach.  After all, Broadcom
> > could build CFE for ARM, and then we'd want to use this same code to parse
> > the CFE-provided data.
> >
> > Also I would suggest getting rid of the #ifdefs for the flash type, and
> > probing it dynamically instead.  The flash setup code under drivers/ssb/
> > and drivers/bcma/ sets up platform_devices for the flash, right?  If so
> > then it would be best if this code could run after the bus setup code,
> > query the Linux device model for the type of platform flash in use, and
> > then extract the appropriate address space to probe from that data.
> 
> I'm pretty sure you look at some old version of arch/bcm47xx/nvram.c.
> I wouldn't dare to move such a MIPS-focused driver to some common
> place ;)
> 
> Please check for the version of nvram.c in Ralf's upstream-sfr tree. I
> think you'll like it much more. Hopefully you will even consider it
> ready for moving to the drivers/firmware/ or whatever :)

OK I will take a look at this, and will either send comments, or will 
send a Reviewed-By:.


Thanks for all of the good discussion on this :-)

- Paul

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