linux-kernel - Re: [PATCH v2 4/6] ARM: tegra: rework fuse.c

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Date:	Mon, 06 Jan 2014 13:50:42 -0700
From:	Stephen Warren <swarren@...dotorg.org>
To:	Peter De Schrijver <pdeschrijver@...dia.com>
CC:	linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Russell King <linux@....linux.org.uk>,
	Thierry Reding <thierry.reding@...il.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Prashant Gaikwad <pgaikwad@...dia.com>,
	Alexandre Courbot <acourbot@...dia.com>,
	Olof Johansson <olof@...om.net>,
	Danny Huang <dahuang@...dia.com>
Subject: Re: [PATCH v2 4/6] ARM: tegra: rework fuse.c

On 12/24/2013 06:32 AM, Peter De Schrijver wrote:
> Reduce fuse.c to the minimum functionality required for the early bootstages.
>
> Also export tegra_read_straps() for use by the fuse driver.

Since the fuse driver is tristate, it could be a module. Doesn't it
literally need to be EXPORT_SYMBOL'd, not simply not static?

I'm rather worried that this series isn't bisectable, since this patch
removes a bunch of code that's replaced by code in the fuse driver which
can't be built/linked at this point in the series. I'm also worried
about initialization ordering, since a lot of the fuse code could be a
module...

> diff --git a/arch/arm/mach-tegra/fuse.c b/arch/arm/mach-tegra/fuse.c

> -/* Tegra20 only */
>  #define FUSE_UID_LOW		0x108
>  #define FUSE_UID_HIGH		0x10c

Why remove that comment but leave the two defines it applies to?

>  #define TEGRA20_FUSE_SPARE_BIT		0x200

That define, and tegra_spare_fuse() which uses it, are no longer used
after patch 5/6, but aren't removed in patch 5/6. Perhaps it'd be better
to squash or re-order the two patches, so this dead code can be removed?

> -int tegra_sku_id;
> -int tegra_cpu_process_id;
> -int tegra_core_process_id;
>  int tegra_chip_id;
> -int tegra_cpu_speedo_id;		/* only exist in Tegra30 and later */
> -int tegra_soc_speedo_id;
>  enum tegra_revision tegra_revision;

It's a bit odd to remove most of this, but leave a few parts hanging
around. Wouldn't it be better to the drivers/misc/fuse code to export
this, so that /all/ the fuse logic was there, rather than part of it
being left over in arch/arm/? We'll need to fix that up anyway when we
start using these globals on ARMv8, so may as well get it right now.
Also, I rather think that the new drivers/misc/fuse code shouldn't be a
module or driver, so that we can guarantee it's always there to provide
the globals and that they are initialized early enough...
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