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cirrusfb: fix clock doubling

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Cirrus' Alpine and Picasso4 chips uses DAC clock doubling to achieve full
range of pixclock frequencies.

[akpm@linux-foundation.org: fix spelling, use usual comment layout]
Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Krzysztof Helt 2009-03-31 15:25:14 -07:00 committed by Linus Torvalds
parent 7cade31cab
commit dd14f71cc6
1 changed files with 18 additions and 1 deletions
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17
drivers/video/cirrusfb.c
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@ -470,9 +470,24 @@ static int cirrusfb_check_pixclock(const struct fb_var_screeninfo *var,
/* If the frequency is greater than we can support, we might be able
* to use multiplexing for the video mode */
if (freq > maxclock) {
dev_err(info->device,
"Frequency greater than maxclock (%ld kHz)\n",
maxclock);
return -EINVAL;
}
/*
* Additional constraint: 8bpp uses DAC clock doubling to allow maximum
* pixel clock
*/
if (var->bits_per_pixel == 8) {
switch (cinfo->btype) {
case BT_ALPINE:
case BT_PICASSO4:
if (freq > 85500)
cinfo->multiplexing = 1;
break;
case BT_GD5480:
if (freq > 135100)
cinfo->multiplexing = 1;
break;
@ -815,6 +830,8 @@ static int cirrusfb_set_par_foo(struct fb_info *info)
freq = PICOS2KHZ(var->pixclock);
if (cinfo->btype == BT_ALPINE && var->bits_per_pixel == 24)
freq *= 3;
if (cinfo->multiplexing)
freq /= 2;
bestclock(freq, &nom, &den, &div);