Re: [PATCH 1/1] ARM iMX28: incorrect frac/div calculation

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On 03/23/2012 12:13 AM, Lothar Waßmann wrote:
Hi,

Matt Burtch writes:
The frac and div values in _CLK_SET_RATE are calculated incorrectly
for some clock rates ie. CPU clk of 454.73MHz, 392.72MHz, 261.81Mhz,
etc.

Now the frac and div values which result in the closest actual clock
rate to that requested is selected.  Also there are no limitations
on what frac values can be used, as long as they fall in the valid
(18<  frac<  35) range.

Tested on custom iMX28 board.

Signed-off-by: Matt Burtch<matt@xxxxxxxxxxxx>
---
  arch/arm/mach-mxs/clock-mx28.c |    8 ++------
  1 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/arm/mach-mxs/clock-mx28.c b/arch/arm/mach-mxs/clock-mx28.c
index 5d68e41..a058b99 100644
--- a/arch/arm/mach-mxs/clock-mx28.c
+++ b/arch/arm/mach-mxs/clock-mx28.c
@@ -354,19 +354,15 @@ static int name##_set_rate(struct clk *clk, unsigned long rate)		\
  		}							\
  		for (d = 1; d<= div_max; d++) {			\
  			f = parent_rate * 18 / d / rate;		\
-			if ((parent_rate * 18 / d) % rate)		\
-				f++;					\
  			if (f<  18 || f>  35)				\
  				continue;				\
  									\
  			calc_rate = parent_rate * 18 / f / d;		\
-			if (calc_rate>  rate)				\
-				continue;				\
  									\
-			if (rate - calc_rate<  diff) {			\
+			if (abs(rate - calc_rate)<  diff) {		\
Shouldn't this actually be '<=' (also in the original code)?
Hi Lothar,

It shouldn't make a difference. If it was '<=' it would result in a different frac and higher div value but the difference between the requested rate and actual would be the same.

Thanks,
Matt Burtch
Lothar Waßmann



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