Re: siliconmotion CSync output ?

On 3/13/07, bruno schwander <[email protected]> wrote:
> On Mon, 12 Mar 2007, Alex Deucher wrote:
>
> > On 3/12/07, bruno schwander <[email protected]> wrote:
> >> I used your vclk setting code as in smi_driver.c, and changed the shift
> >> in SMI_CommonCalcClock() but it seems to still have some
> >> issue.
> >>
> >> 12220 clock gives me values of
> >>
> >> SR6C: 63, SR6D: 1D
> >>
> >
> > That's going to give you a vclk of ~48.88 Mhz
>
> yeah, I know.
>
> I meant that SMI_CommonCalcClock should have come up with different
> values, instead it returned the values above.
>
> > Unfortunately, the min clock on the smi is 20 Mhz (although I'd think
>
> hmm that would be really annoying...where do you get that ? I can't find

that's just what was specified in the driver originally.  smi wrote it...

> any mention of such a limitation. Just the hope that given the right
> SR6C/D values, I can get any corresponding dot clock :-)
>

try bumping the max n1 up.  see my newest code below.

> I did chnge the minclock values so that it accepts lower clock requests,
> but I have not checked it it actually generates those frequencies. Need
> the scope...
>

Good luck!  let me know how it goes.

> > you should be able to get down to at least the reference clock), so
> > that may be causing a problem in the calculation function.  If you
> > want to calculate the clock yourself you can use the following
> > formula:
> >
> > VCLK = 14.31818 Mhz * (VNR/VDR) * (1/(1 + PS))
> >
> > VNR being SR6C and VDR and SR6D.  PS is bit 7 of SR6D.
>
> the spec I have for the smi712 (lynxEM+) says bit 7 and 6 are PS,
> as follows:
>
> bit 6  bit 7      vclk
> 0      0          PS not enabled, programmed vclk
> 0      1          PS enabled, vclk = 1/2 programmed vclk
> 1      0          PS enabled, vclk = 1/4 prog vlck
> 1      1          PS enabled, vclk = 1/8 prog vlck

Ah, I was reading the 722 book.  I didn't realize the 712 had 2 bits
for PS; you might have more luck in that case.  I fixed up the driver
to deal with this and set the proper min/max values for the
calculation.
http://gitweb.freedesktop.org/?p=xorg/driver/xf86-video-siliconmotion.git;a=summary

Alex

>
>
> bruno