Re: [PATCH 1/6] clk: at91: clk-generated: remove useless divisor loop
From: Boris Brezillon <hidden>
Date: 2017-07-03 13:58:41
Also in:
alsa-devel, linux-arm-kernel, linux-clk, lkml
On Fri, 23 Jun 2017 11:00:54 +0200 Quentin Schulz [off-list ref] wrote:
The driver requests the current clk rate of each of its parent clocks to decide whether a clock rate is suitable or not. It does not request determine_rate from a parent clock which could request a rate change in parent clock (i.e. there is no parent rate propagation). We know the rate we want (passed along req argument of the function) and the parent clock rate, thus we know the closest rounded divisor, we don't need to iterate over the available divisors to find the best one for a given clock. Signed-off-by: Quentin Schulz <redacted>
Acked-by: Boris Brezillon <redacted>
quoted hunk ↗ jump to hunk
--- drivers/clk/at91/clk-generated.c | 25 ++++++++++++------------- 1 file changed, 12 insertions(+), 13 deletions(-)diff --git a/drivers/clk/at91/clk-generated.c b/drivers/clk/at91/clk-generated.c index 07c8f701e51c..dab7002937e6 100644 --- a/drivers/clk/at91/clk-generated.c +++ b/drivers/clk/at91/clk-generated.c@@ -124,19 +124,18 @@ static int clk_generated_determine_rate(struct clk_hw *hw, (gck->range.max && min_rate > gck->range.max)) continue; - for (div = 1; div < GENERATED_MAX_DIV + 2; div++) { - tmp_rate = DIV_ROUND_CLOSEST(parent_rate, div); - tmp_diff = abs(req->rate - tmp_rate); - - if (best_diff < 0 || best_diff > tmp_diff) { - best_rate = tmp_rate; - best_diff = tmp_diff; - req->best_parent_rate = parent_rate; - req->best_parent_hw = parent; - } - - if (!best_diff || tmp_rate < req->rate) - break; + div = DIV_ROUND_CLOSEST(parent_rate, req->rate); + if (!div) + tmp_rate = parent_rate; + else + tmp_rate = parent_rate / div; + tmp_diff = abs(req->rate - tmp_rate); + + if (best_diff < 0 || best_diff > tmp_diff) { + best_rate = tmp_rate; + best_diff = tmp_diff; + req->best_parent_rate = parent_rate; + req->best_parent_hw = parent; } if (!best_diff)