From d6205a1878dd4cc9664c4b4829b68a29c0426efc Mon Sep 17 00:00:00 2001 From: Taniya Das Date: Mon, 5 Jan 2026 16:09:50 +0530 Subject: [PATCH] clk: qcom: rcg2: compute 2d using duty fraction directly MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit The duty-cycle calculation in clk_rcg2_set_duty_cycle() currently derives an intermediate percentage `duty_per = (num * 100) / den` and then computes: d = DIV_ROUND_CLOSEST(n * duty_per * 2, 100); This introduces integer truncation at the percentage step (division by `den`) and a redundant scaling by 100, which can reduce precision for large `den` and skew the final rounding. Compute `2d` directly from the duty fraction to preserve precision and avoid the unnecessary scaling: d = DIV_ROUND_CLOSEST(n * duty->num * 2, duty->den); This keeps the intended formula `d ≈ n * 2 * (num/den)` while performing a single, final rounded division, improving accuracy especially for small duty cycles or large denominators. It also removes the unused `duty_per` variable, simplifying the code. There is no functional changes beyond improved numerical accuracy. Fixes: 7f891faf596ed ("clk: qcom: clk-rcg2: Add support for duty-cycle for RCG") Signed-off-by: Taniya Das Link: https://lore.kernel.org/r/20260105-duty_cycle_precision-v2-1-d1d466a6330a@oss.qualcomm.com Signed-off-by: Bjorn Andersson --- drivers/clk/qcom/clk-rcg2.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/drivers/clk/qcom/clk-rcg2.c b/drivers/clk/qcom/clk-rcg2.c index e18cb8807d73..2838d4cb2d58 100644 --- a/drivers/clk/qcom/clk-rcg2.c +++ b/drivers/clk/qcom/clk-rcg2.c @@ -755,7 +755,7 @@ static int clk_rcg2_get_duty_cycle(struct clk_hw *hw, struct clk_duty *duty) static int clk_rcg2_set_duty_cycle(struct clk_hw *hw, struct clk_duty *duty) { struct clk_rcg2 *rcg = to_clk_rcg2(hw); - u32 notn_m, n, m, d, not2d, mask, duty_per, cfg; + u32 notn_m, n, m, d, not2d, mask, cfg; int ret; /* Duty-cycle cannot be modified for non-MND RCGs */ @@ -774,10 +774,8 @@ static int clk_rcg2_set_duty_cycle(struct clk_hw *hw, struct clk_duty *duty) n = (~(notn_m) + m) & mask; - duty_per = (duty->num * 100) / duty->den; - /* Calculate 2d value */ - d = DIV_ROUND_CLOSEST(n * duty_per * 2, 100); + d = DIV_ROUND_CLOSEST(n * duty->num * 2, duty->den); /* * Check bit widths of 2d. If D is too big reduce duty cycle. -- 2.47.3