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SubjectRe: [PATCH v2 4/4] clk: at91: optimization of the determine_rate callback
Hi JJ,

I guess you're commit message is wrong: you're optimizing set_rate not
determine_rate.

Best Regards,

Boris

On 05/02/2014 09:37, Jean-Jacques Hiblot wrote:
> Signed-off-by: Boris BREZILLON <b.brezillon@overkiz.com>
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com>
> ---
> drivers/clk/at91/clk-programmable.c | 38 ++++++++-----------------------------
> 1 file changed, 8 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/clk/at91/clk-programmable.c b/drivers/clk/at91/clk-programmable.c
> index 7bcc725..62e2509 100644
> --- a/drivers/clk/at91/clk-programmable.c
> +++ b/drivers/clk/at91/clk-programmable.c
> @@ -139,43 +139,21 @@ static int clk_programmable_set_rate(struct clk_hw *hw, unsigned long rate,
> struct clk_programmable *prog = to_clk_programmable(hw);
> struct at91_pmc *pmc = prog->pmc;
> const struct clk_programmable_layout *layout = prog->layout;
> - unsigned long best_rate = parent_rate;
> - unsigned long best_diff;
> - unsigned long new_diff;
> - unsigned long cur_rate;
> + unsigned long div = parent_rate / rate;
> int shift = 0;
> u32 tmp = pmc_read(pmc, AT91_PMC_PCKR(prog->id)) &
> ~(PROG_PRES_MASK << layout->pres_shift);
>
> - if (rate > parent_rate)
> - return parent_rate;
> - else
> - best_diff = parent_rate - rate;
> + if (!div)
> + return -EINVAL;
>
> - if (!best_diff) {
> - pmc_write(pmc, AT91_PMC_PCKR(prog->id), tmp | shift);
> - return 0;
> - }
> -
> - for (shift = 1; shift < PROG_PRES_MASK; shift++) {
> - cur_rate = parent_rate >> shift;
> -
> - if (cur_rate > rate)
> - new_diff = cur_rate - rate;
> - else
> - new_diff = rate - cur_rate;
> -
> - if (!new_diff)
> - break;
> + shift = fls(div) - 1;
>
> - if (new_diff < best_diff) {
> - best_diff = new_diff;
> - best_rate = cur_rate;
> - }
> + if (div != (1<<shift))
> + return -EINVAL;
>
> - if (rate > cur_rate)
> - break;
> - }
> + if (shift >= PROG_PRES_MASK)
> + return -EINVAL;
>
> pmc_write(pmc, AT91_PMC_PCKR(prog->id),
> tmp | (shift << layout->pres_shift));



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