On Tue, Nov 20, 2018 at 11:39:26AM +0100, Maarten Lankhorst wrote:
> On lynxpoint the bios sometimes sets up the backlight using the CPU
> display, but the driver expects using the PWM PCH override register.
>
> Read the value from the CPU register, then convert it to the other
> units by converting from the old duty cycle, to freq, to the new units.
>
> This value is then programmed in the override register, after which
> we set the override and disable the CPU display control. This allows
> us to switch the source without flickering, and make the backlight
> controls work in the driver.
>
> Signed-off-by: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108225
> Cc: Basil Eric Rabi <ericbasil.r...@gmail.com>
> Cc: Hans de Goede <jwrdego...@fedoraproject.org>
> Cc: Tolga Cakir <cevel...@gmail.com>
> Tested-by: Tolga Cakir <cevel...@gmail.com>
> ---
> drivers/gpu/drm/i915/intel_panel.c | 34 +++++++++++++++++++++++++++---
> 1 file changed, 31 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_panel.c
> b/drivers/gpu/drm/i915/intel_panel.c
> index e6cd7b55c018..3357232f1b0e 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -1485,7 +1485,7 @@ static int lpt_setup_backlight(struct intel_connector
> *connector, enum pipe unus
> struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
> struct intel_panel *panel = &connector->panel;
> u32 pch_ctl1, pch_ctl2, val;
> - bool alt;
> + bool alt, cpu_mode = false;
>
> if (HAS_PCH_LPT(dev_priv))
> alt = I915_READ(SOUTH_CHICKEN2) & LPT_PWM_GRANULARITY;
> @@ -1507,12 +1507,40 @@ static int lpt_setup_backlight(struct intel_connector
> *connector, enum pipe unus
>
> panel->backlight.min = get_backlight_min_vbt(connector);
>
> - val = lpt_get_backlight(connector);
> + panel->backlight.enabled = pch_ctl1 & BLM_PCH_PWM_ENABLE;
> + if (panel->backlight.enabled && HAS_PCH_LPT(dev_priv) &&
> + (I915_READ(BLC_PWM_CPU_CTL2) & BLM_PWM_ENABLE) &&
> + !WARN_ON(pch_ctl1 & BLM_PCH_OVERRIDE_ENABLE)) {
> + u32 freq;
> +
> + cpu_mode = true;
> + /*
> + * We're in cpu mode, convert to PCH units.
> + *
> + * Convert CPU pwm tick back to hz, back to new PCH units again.
> + * this is the same formula as pch_hz_to_pwm, but the other way
> + * around..
> + */
> + val = pch_get_backlight(connector);
> + freq = DIV_ROUND_CLOSEST(KHz(dev_priv->rawclk_freq), val * 128);
The docs are telling me that HSW/BDW use cdclk for the CPU backlight,
and the increment is configurable as well.
Also what about S4 resume? Don't we need this trick there as well?
> +
> + val = lpt_hz_to_pwm(connector, freq);
> + } else
> + val = lpt_get_backlight(connector);
> val = intel_panel_compute_brightness(connector, val);
> panel->backlight.level = clamp(val, panel->backlight.min,
> panel->backlight.max);
>
> - panel->backlight.enabled = pch_ctl1 & BLM_PCH_PWM_ENABLE;
> + if (cpu_mode) {
> + u32 tmp;
> +
> + /* Use PWM mode, instead of cpu clock */
> + lpt_set_backlight(connector->base.state,
> panel->backlight.level);
> + I915_WRITE(BLC_PWM_PCH_CTL1, pch_ctl1 |
> BLM_PCH_OVERRIDE_ENABLE);
> +
> + tmp = I915_READ(BLC_PWM_CPU_CTL2);
> + I915_WRITE(BLC_PWM_CPU_CTL2, tmp & ~BLM_PWM_ENABLE);
> + }
>
> return 0;
> }
> --
> 2.19.1
>
> _______________________________________________
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> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
--
Ville Syrjälä
Intel
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