On Mon, 5 Dec 2011, Paul Walmsley wrote:
> For example, here's a trivial implementation for rate recalculation for a
> integer divider clock node (that can't be handled with a right shift):
>
> s64 div(struct clk *clk, u32 div) {
> if (clk->flags & CLK_PARENT_RATE_MAX_U32)
> return ((u32)(clk->parent->rate & 0xffffffff)) / div;
>
> clk->rate = clk->parent->rate;
> do_div(clk->rate, div);
> return clk->rate;
> }
(removing some useless cruft from the above function, for clarity's sake)
s64 div(struct clk *clk, u32 div) {
s64 r;
if (clk->flags & CLK_PARENT_RATE_MAX_U32)
return ((u32)clk->parent->rate) / div;
r = clk->parent->rate;
do_div(r, div);
return r;
}
00000000 <div>:
0: e92d4010 push {r4, lr}
4: e1a04001 mov r4, r1
8: e5d03010 ldrb r3, [r0, #16]
c: e3130001 tst r3, #1
10: 1a000005 bne 2c <div+0x2c>
14: e5903000 ldr r3, [r0]
18: e1c300d8 ldrd r0, [r3, #8]
1c: ebfffffe bl 0 <__do_div64>
20: e1a00002 mov r0, r2
24: e1a01003 mov r1, r3
28: e8bd8010 pop {r4, pc}
2c: e5900000 ldr r0, [r0]
30: e5900008 ldr r0, [r0, #8]
34: ebfffffe bl 0 <__aeabi_uidiv>
38: e3a01000 mov r1, #0
3c: e8bd8010 pop {r4, pc}
- Paul
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