| Message ID | 1332457501-8153-1-git-send-email-matt@grid-net.com |
|---|---|
| State | New |
| Headers | show |
On Thu, Mar 22, 2012 at 04:05:01PM -0700, Matt Burtch wrote: > 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. My understanding on clk_set_rate is we need to set the clk to a rate closest to the requested one but never exceeding it. Does your change ensure that? Regards, Shawn > 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@grid-net.com> > --- > 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) { \ > frac = f; \ > div = d; \ > - diff = rate - calc_rate; \ > + diff = abs(rate - calc_rate); \ > } \ > \ > if (diff == 0) \ > -- > 1.7.5.4 >
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@grid-net.com> > --- > 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)? Lothar Waßmann
On 03/22/2012 07:52 PM, Shawn Guo wrote: > On Thu, Mar 22, 2012 at 04:05:01PM -0700, Matt Burtch wrote: >> 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. > My understanding on clk_set_rate is we need to set the clk to a rate > closest to the requested one but never exceeding it. Does your change > ensure that? > > Regards, > Shawn It currently doesn't check that the resultant clock is lower than the requested. I can certainly make that change and resubmit. I wasn't aware of this requirement. So with the patch as it stands, if you request a CPU clock of 391Mhz, it'll give you 392.71MHz. Would it be correct for the clock to be set at 375.65MHz (the next closest valid clock rate without going over)? Thanks, Matt >> 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@grid-net.com> >> --- >> 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) { \ >> frac = f; \ >> div = d; \ >> - diff = rate - calc_rate; \ >> + diff = abs(rate - calc_rate); \ >> } \ >> \ >> if (diff == 0) \ >> -- >> 1.7.5.4 >>
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@grid-net.com> >> --- >> 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
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) { \ frac = f; \ div = d; \ - diff = rate - calc_rate; \ + diff = abs(rate - calc_rate); \ } \ \ if (diff == 0) \
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@grid-net.com> --- arch/arm/mach-mxs/clock-mx28.c | 8 ++------ 1 files changed, 2 insertions(+), 6 deletions(-)