[PATCH v2 4/4] clk: at91: optimization of the determine_rate callback

From: Jean-Jacques Hiblot
Date: Wed Feb 05 2014 - 03:41:22 EST


Signed-off-by: Boris BREZILLON <b.brezillon@xxxxxxxxxxx>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@xxxxxxxxxxxxxxx>
---
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));
--
1.8.5.2

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