Commit dd14f71c authored by Krzysztof Helt's avatar Krzysztof Helt Committed by Linus Torvalds
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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: default avatarKrzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7cade31c

drivers/video/cirrusfb.c

+18 −1
Original line number Diff line number Diff line
@@ -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);

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