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drm/i915/pch: Use minimal number of FDI lanes (v2)

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This should be a small power savings. Tested on Lenovo T410 (Ironlake), LVDS
VGA and DisplayPort, up to 1920x1200R.

v2: Add Sandybridge support, fix obvious math error.

Acked-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
This commit is contained in:
Adam Jackson 2010-04-12 11:38:44 -04:00 committed by Eric Anholt
parent 7f8a85698f
commit 77ffb5979d
2 changed files with 21 additions and 6 deletions
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26
drivers/gpu/drm/i915/intel_display.c
View File

@ -1507,7 +1507,8 @@ static void ironlake_fdi_link_train(struct drm_crtc *crtc)
/* enable CPU FDI TX and PCH FDI RX */
temp = I915_READ(fdi_tx_reg);
temp |= FDI_TX_ENABLE;
temp |= FDI_DP_PORT_WIDTH_X4; /* default */
temp &= ~(7 << 19);
temp |= (intel_crtc->fdi_lanes - 1) << 19;
temp &= ~FDI_LINK_TRAIN_NONE;
temp |= FDI_LINK_TRAIN_PATTERN_1;
I915_WRITE(fdi_tx_reg, temp);
@ -1607,7 +1608,8 @@ static void gen6_fdi_link_train(struct drm_crtc *crtc)
/* enable CPU FDI TX and PCH FDI RX */
temp = I915_READ(fdi_tx_reg);
temp |= FDI_TX_ENABLE;
temp |= FDI_DP_PORT_WIDTH_X4; /* default */
temp &= ~(7 << 19);
temp |= (intel_crtc->fdi_lanes - 1) << 19;
temp &= ~FDI_LINK_TRAIN_NONE;
temp |= FDI_LINK_TRAIN_PATTERN_1;
temp &= ~FDI_LINK_TRAIN_VOL_EMP_MASK;
@ -1769,8 +1771,9 @@ static void ironlake_crtc_dpms(struct drm_crtc *crtc, int mode)
*/
temp &= ~(0x7 << 16);
temp |= (pipe_bpc << 11);
I915_WRITE(fdi_rx_reg, temp | FDI_RX_PLL_ENABLE |
FDI_DP_PORT_WIDTH_X4); /* default 4 lanes */
temp &= ~(7 << 19);
temp |= (intel_crtc->fdi_lanes - 1) << 19;
I915_WRITE(fdi_rx_reg, temp | FDI_RX_PLL_ENABLE);
I915_READ(fdi_rx_reg);
udelay(200);
@ -3368,7 +3371,7 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
/* FDI link */
if (HAS_PCH_SPLIT(dev)) {
int lane, link_bw, bpp;
int lane = 0, link_bw, bpp;
/* eDP doesn't require FDI link, so just set DP M/N
according to current link config */
if (is_edp) {
@ -3382,7 +3385,6 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
target_clock = mode->clock;
else
target_clock = adjusted_mode->clock;
lane = 4;
link_bw = 270000;
}
@ -3434,6 +3436,18 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
bpp = 24;
}
if (!lane) {
/*
* Account for spread spectrum to avoid
* oversubscribing the link. Max center spread
* is 2.5%; use 5% for safety's sake.
*/
u32 bps = target_clock * bpp * 21 / 20;
lane = bps / (link_bw * 8) + 1;
}
intel_crtc->fdi_lanes = lane;
ironlake_compute_m_n(bpp, lane, target_clock, link_bw, &m_n);
}

1
drivers/gpu/drm/i915/intel_drv.h
View File

@ -152,6 +152,7 @@ struct intel_crtc {
bool lowfreq_avail;
struct intel_overlay *overlay;
struct intel_unpin_work *unpin_work;
int fdi_lanes;
};
#define to_intel_crtc(x) container_of(x, struct intel_crtc, base)