2013/10/24 Ben Widawsky <benjamin.widawsky@xxxxxxxxx>:
> We were turning this on for SNB regardless of whether or not we use FBC.
> We can save the slightest amount of power if we don't disable it when
> not using FBC.
>
> The workaround should be bit 9 for SNB.
First, see comment in patch 3. So you're removing the WA on ILK and
applying it for SNB-only. Since the spec doesn't say "SNB only", I
guess we need this WA on both gens.
>
> Signed-off-by: Ben Widawsky <ben@xxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_pm.c | 25 +++++++++++++++----------
> 1 file changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index bbcf100..4ebbe65 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -237,6 +237,12 @@ static void ironlake_enable_fbc(struct drm_crtc *crtc, unsigned long interval)
> I915_WRITE(SNB_DPFC_CTL_SA,
> SNB_CPU_FENCE_ENABLE | obj->fence_reg);
> I915_WRITE(DPFC_CPU_FENCE_OFFSET, crtc->y);
> +
> + /* WaFbcDisableDpfcClockGating:snb */
> + I915_WRITE(ILK_DSPCLK_GATE_D,
> + I915_READ(ILK_DSPCLK_GATE_D) |
> + ILK_DPFCUNIT_CLOCK_GATE_DISABLE);
> +
> sandybridge_blit_fbc_update(dev);
> } else {
> /* WaFbcDisableDpfcClockGating:ilk */
> @@ -259,7 +265,12 @@ static void ironlake_disable_fbc(struct drm_device *dev)
> dpfc_ctl &= ~DPFC_CTL_EN;
> I915_WRITE(ILK_DPFC_CONTROL, dpfc_ctl);
>
> - if (IS_GEN5(dev))
> + if (IS_GEN6(dev))
> + /* WaFbcDisableDpfcClockGating:snb */
> + I915_WRITE(ILK_DSPCLK_GATE_D,
> + I915_READ(ILK_DSPCLK_GATE_D) &
> + ~ILK_DPFCUNIT_CLOCK_GATE_DISABLE);
> + else if (IS_GEN5(dev))
> /* WaFbcDisableDpfcClockGating:ilk */
> I915_WRITE(ILK_DSPCLK_GATE_D,
> I915_READ(ILK_DSPCLK_GATE_D) &
> @@ -4939,15 +4950,9 @@ static void g4x_disable_trickle_feed(struct drm_device *dev)
> static void ironlake_init_clock_gating(struct drm_device *dev)
> {
> struct drm_i915_private *dev_priv = dev->dev_private;
> - uint32_t dspclk_gate = ILK_VRHUNIT_CLOCK_GATE_DISABLE;
> -
> - /*
> - * Required for FBC
> - * WaFbcDisableDpfcClockGating:snb
> - */
> - dspclk_gate |=
> - ILK_DPFCUNIT_CLOCK_GATE_DISABLE |
> - ILK_DPFDUNIT_CLOCK_GATE_ENABLE;
> + uint32_t dspclk_gate =
> + ILK_VRHUNIT_CLOCK_GATE_DISABLE |
> + ILK_DPFDUNIT_CLOCK_GATE_ENABLE;
>
> I915_WRITE(PCH_3DCGDIS0,
> MARIUNIT_CLOCK_GATE_DISABLE |
> --
> 1.8.4.1
>
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--
Paulo Zanoni
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