[U-Boot] [PATCH 2/6] ARM: tegra: rename MASK_BITS_29_28 to MASK_BITS_31_28

[Thierry Reding <thierry.reding@gmail.com>]

On Wed, Jan 22, 2014 at 01:20:32PM -0700, Stephen Warren wrote:
> From: Stephen Warren <swarren@nvidia.com>
> 
> The only place where the MASK_BITS_* values are used is in
> adjust_periph_pll(), which interprets the value 4 (old MASK_BITS_29_28,
> new MASK_BITS_31_28) as being associated with mask OUT_CLK_SOURCE4_MASK,
> i.e. bits 31:28. Rename the MASK_BITS_ macro to reflect how it's actually
> implemented.
> 
> Note that no Tegra clock register actually uses all of bits 31:28 as
> the mux field. Rather, bits 30:28, 29:28, or 28 are used. However, in
> those cases, nothing is stored in the bits about the mux field, so it's

s/about/above/ perhaps?

> safe to pretend that the mux field extends all the way to the end of the
> register. As such, the U-Boot clock driver is currently a bit lazy, and
> doesn't distinguish between 31:28, 30:28, 29:29 and 29; it just lumps

Shouldn't that list be: "31:28, 30:28, 29:28 and 28"?

> them all together and pretends they're all 31:28. This patch doesn't
> cause this issue; it was pre-existing. Hopefully, future patches will
> clean this up.

Yes, that'd be nice.

> diff --git a/arch/arm/include/asm/arch-tegra/clock.h b/arch/arm/include/asm/arch-tegra/clock.h
[...]
> +/*
> + * Note that no Tegra clock register actually uses all of bits 31:28 as
> + * the mux field. Rather, bits 30:28, 29:28, or 28 are used. However, in
> + * those cases, nothing is stored in the bits about the mux field, so it's
> + * safe to pretend that the mux field extends all the way to the end of the
> + * register. As such, the U-Boot clock driver is currently a bit lazy, and
> + * doesn't distinguish between 31:28, 30:28, 29:29 and 29; it just lumps

The list seems wrong here as well, but it looks like it's copy/pasted to
or from the commit message.

>  enum {
>  	MASK_BITS_31_30	= 2,	/* num of bits used to specify clock source */
>  	MASK_BITS_31_29,
> -	MASK_BITS_29_28,
> +	MASK_BITS_31_28,
>  };

If this ever gets cleaned up I think it'd be clearer to explicitly
define them to the number of bits that they use by turning them into
#defines.

Thierry
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