[U-Boot] [PATCH v3 11/18] arm: Add control over cachability of memory regions

[Mike Frysinger <vapier@gentoo.org>]

On Thursday 12 July 2012 14:12:41 Albert ARIBAUD wrote:
> On Thu, 12 Jul 2012 08:25:11 -0700, Simon Glass wrote:
> > --- a/arch/arm/include/asm/system.h
> > +++ b/arch/arm/include/asm/system.h
> > 
> > +/* options available for data cache on each page */
> > +enum dcache_option {
> > +	DCACHE_OFF,
> > +	DCACHE_WRITETHROUGH,
> > +	DCACHE_WRITEBACK,
> > +};
> >
> > --- a/arch/arm/lib/cache-cp15.c
> > +++ b/arch/arm/lib/cache-cp15.c
> > 
> > -static inline void dram_bank_mmu_setup(int bank)
> > +void set_section_dcache(int section, enum dcache_option option)
> >  {
> > +	u32 value = section << MMU_SECTION_SHIFT | (3 << 10);
> >  	u32 *page_table = (u32 *)gd->tlb_addr;
> > +
> > +	switch (option) {
> > +	case DCACHE_WRITETHROUGH:
> > +		value |= 0x1a;
> > +		break;
> > +
> > +	case DCACHE_WRITEBACK:
> > +		value |= 0x1e;
> > +		break;
> > +
> > +	case DCACHE_OFF:
> > +		value |= 0x12;
> > +		break;
> > +	}
> 
> what's the benefit of introducing an arbitrary enum rather than
> defining DCACHE_WRITETHROUGH, DCACHE_WRITEBACK and DCACHE_OFF equal
> respecitvely to 0x1a, 0x1e and 0x12? All it does is force this
> switch case instead of a simple 'value |= option;' statement.

if these magic bitmasks are going to be the same for all arm cores (the enum 
is in common arm header), then you can get the advantages of both:
enum dcache_option {
	DCACHE_OFF = 0x12,
	DCACHE_WRITETHROUGH = 0x1a,
	DCACHE_WRITEBACK = 0x1e,
};

then just do:
	value |= option;
-mike
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