[U-Boot] [PATCH 2/6] arch: bcm281xx: Initial commit of bcm281xx architecture code

[Matt Porter]

On Wed, Jan 29, 2014 at 05:32:30PM -0500, Tom Rini wrote:
> On Mon, Jan 27, 2014 at 10:53:26AM -0800, Darwin Rambo wrote:
> 
> > Add bcm281xx architecture support code including a clock framework and
> > chip reset.  Define register block base addresses for the bcm281xx
> > architecture and create an empty gpio header file required when
> > CONFIG_CMD_GPIO is set.
> [snip]
> > +/* Bitfield operations */
> > +
> > +/* Produces a mask of set bits covering a range of a 32-bit value */
> > +static inline u32 bitfield_mask(u32 shift, u32 width)
> > +{
> > +	return ((1 << width) - 1) << shift;
> > +}
> > +
> > +/* Extract the value of a bitfield found within a given register value */
> > +static inline u32 bitfield_extract(u32 reg_val, u32 shift, u32 width)
> > +{
> > +	return (reg_val & bitfield_mask(shift, width)) >> shift;
> > +}
> > +
> > +/* Replace the value of a bitfield found within a given register value */
> > +static inline u32 bitfield_replace(u32 reg_val, u32 shift, u32 width, u32 val)
> > +{
> > +	u32 mask = bitfield_mask(shift, width);
> > +
> > +	return (reg_val & ~mask) | (val << shift);
> > +}
> 
> This all feels horribly generic, isn't there some linux header we've
> already got that I can't think off of the top of my head that gives us
> these kind of functions?

To add to what Darwin mentioned about bitops.h being insufficient...

The equivalent kernel implementations are wrapped up in the
regmap/regmap-mmio helpers. That implementation is *very* heavyweight,
and IMHO simply not appropriate for U-Boot (and often not useful in the
kernel as well).  A homegrown generic set of inline ops would seem to be
ideal for U-Boot.

-Matt