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drm/radeon/kms: add PLL flag to prefer frequencies <= the target freq 

This is needed when using fractional feedback dividers on some IGP
chips.

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Alex Deucher 2009-07-13 11:08:18 -04:00 committed by Dave Airlie
parent b995e4330d
commit d0e275a90a
2 changed files with 6 additions and 1 deletions
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6
drivers/gpu/drm/radeon/radeon_display.c
View File

@ -491,7 +491,11 @@ void radeon_compute_pll(struct radeon_pll *pll,
tmp += (uint64_t)pll->reference_freq * 1000 * frac_feedback_div;
current_freq = radeon_div(tmp, ref_div * post_div);
error = abs(current_freq - freq);
if (flags & RADEON_PLL_PREFER_CLOSEST_LOWER) {
error = freq - current_freq;
error = error < 0 ? 0xffffffff : error;
} else
error = abs(current_freq - freq);
vco_diff = abs(vco - best_vco);
if ((best_vco == 0 && error < best_error) ||

1
drivers/gpu/drm/radeon/radeon_mode.h
View File

@ -124,6 +124,7 @@ struct radeon_tmds_pll {
#define RADEON_PLL_PREFER_LOW_POST_DIV (1 << 8)
#define RADEON_PLL_PREFER_HIGH_POST_DIV (1 << 9)
#define RADEON_PLL_USE_FRAC_FB_DIV (1 << 10)
#define RADEON_PLL_PREFER_CLOSEST_LOWER (1 << 11)
struct radeon_pll {
uint16_t reference_freq;