cirrusfb: fix clock doubling
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>
diff --git a/drivers/video/cirrusfb.c b/drivers/video/cirrusfb.c
index 65a1831..15e2e6b 100644
--- a/drivers/video/cirrusfb.c
+++ b/drivers/video/cirrusfb.c
@@ -470,10 +470,25 @@
/* 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:
- cinfo->multiplexing = 1;
+ if (freq > 135100)
+ cinfo->multiplexing = 1;
break;
default:
@@ -815,6 +830,8 @@
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);
