On Thu, 29 Jan 2009, Russell King - ARM Linux wrote:
> On Thu, Jan 29, 2009 at 03:14:01PM +0000, Russell King - ARM Linux wrote:
> > On Wed, Jan 28, 2009 at 12:27:59PM -0700, Paul Walmsley wrote:
> > > The price paid is additional runtime memory consumption - 8 bytes per
> > > clock and 16 bytes per child clock - roughly 4.5KiB on OMAP3.
> >
> > For OMAP3, that's 222 struct clks of which 182 are children, and indeed
> > 222 * 8 + 182 * 16 gives about 4.5K. On OMAP2, it's 140 and 136,
> > giving 140 * 8 + 136 * 16 = 3.3K.
> >
> > Moving struct clk_child into struct clk means that its clk and flags
> > members can be deleted, making it 8 bytes in size - effectively just
> > the list_head. We need a list_head for the 'children' as you have it.
> > So, that works out as 16 bytes per clock. That gives 3.5K on OMAP3
> > and 2.2K on OMAP2.
> >
> > So, by taking that alternative approach, not only do you end up using
> > less memory, but you also don't have to have the overhead of your
> > custom memory bookkeeping.
> >
> > The other change I'd suggest is that you have one function which deals
> > with setting the parent of a clock:
> >
> > void clk_reparent(struct clk *child, struct clk *parent)
> > {
> > list_del_init(&child->sibling);
> > if (parent)
> > list_add(&child->sibling, &parent->children);
> > child->parent = parent;
> >
> > /* now do the debugfs renaming to reattach the child
> > to the proper parent */
> > }
> >
> > which is a lot simpler than your omap_clk_add_child() and omap_clk_del_child().
> >
> > These should be in the _core_ OMAP clock code, not just in the OMAP2
> > clock code. OMAP1 has child clocks as well as OMAP2.
>
> And here is my version of this patch:
Thanks, I'll take a closer look at this later today.
- Paul
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