[PATCH] rtc: ac100: Program clock divider encodings without subtracting one

[PATCH] rtc: ac100: Program clock divider encodings without subtracting one

[Zhu Jun]

divider_get_val() already returns the hardware encoding for the
power-of-two divider, and ac100_clkout_prediv[].val is also a register
encoding. Subtracting one from either value programs the previous
divider setting and turns encoding zero into all ones.

For example, selecting a 32768 Hz output from the 32768 Hz parent
programs divider seven and produces 256 Hz. Write both encodings
directly so the programmed rate agrees with the requested rate.

Fixes: 04940631b8d2 ("rtc: ac100: Add clk output support")
Signed-off-by: Zhu Jun <zhujun2@cmss.chinamobile.com>
---
 drivers/rtc/rtc-ac100.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-ac100.c b/drivers/rtc/rtc-ac100.c
index be57a33ecf53..a94248346bf3 100644
--- a/drivers/rtc/rtc-ac100.c
+++ b/drivers/rtc/rtc-ac100.c
@@ -243,8 +243,8 @@ static int ac100_clkout_set_rate(struct clk_hw *hw, unsigned long rate,
 	regmap_update_bits(clk->regmap, clk->offset,
 			   ((1 << AC100_CLKOUT_DIV_WIDTH) - 1) << AC100_CLKOUT_DIV_SHIFT |
 			   ((1 << AC100_CLKOUT_PRE_DIV_WIDTH) - 1) << AC100_CLKOUT_PRE_DIV_SHIFT,
-			   (div - 1) << AC100_CLKOUT_DIV_SHIFT |
-			   (pre_div - 1) << AC100_CLKOUT_PRE_DIV_SHIFT);
+			   div << AC100_CLKOUT_DIV_SHIFT |
+			   pre_div << AC100_CLKOUT_PRE_DIV_SHIFT);
 
 	return 0;
 }
-- 
2.51.0

Re: [PATCH] rtc: ac100: Program clock divider encodings without subtracting one

[sashiko-bot]

> divider_get_val() already returns the hardware encoding for the
> power-of-two divider, and ac100_clkout_prediv[].val is also a register
> encoding. Subtracting one from either value programs the previous
> divider setting and turns encoding zero into all ones.
> 
> For example, selecting a 32768 Hz output from the 32768 Hz parent
> programs divider seven and produces 256 Hz. Write both encodings
> directly so the programmed rate agrees with the requested rate.
> 
> Fixes: 04940631b8d2 ("rtc: ac100: Add clk output support")
> Signed-off-by: Zhu Jun <zhujun2@cmss.chinamobile.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261112071620.154398-1-zhujun2@cmss.chinamobile.com?part=1