From: Ben Widawsky <benjamin.widawsky@xxxxxxxxx> On VLV specifically, going too low runs the risk of getting the BLC_EN signal out of sync, preventing resume from working correctly. Scale /sys/class/backlight at this level to prevent userspace from doing this on suspend. This gets rid of the explicitly hardcoded value for a previous/similar patch. Instead relies on the VBT to provide the value, and if VBT does not provide one, then it uses a hardcoded 5% min duty cycle. This was defined a couple patches ago for the same fallback on VLV. Signed-off-by: Ben Widawsky <ben@xxxxxxxxxxxx> Signed-off-by: Wayne Boyer <wayne.boyer@xxxxxxxxx> Change-Id: Ibbbc33338ef1659d0f797d6a33d3727a45ad95d5 Reviewed-on: https://chromium-review.googlesource.com/196609 Reviewed-by: Aaron Durbin <adurbin@xxxxxxxxxxxx> Tested-by: Wayne Boyer <wayne.boyer@xxxxxxxxx> Commit-Queue: Wayne Boyer <wayne.boyer@xxxxxxxxx> Conflicts: drivers/gpu/drm/i915/intel_panel.c --- drivers/gpu/drm/i915/intel_panel.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c index b3327d0..02248a5 100644 --- a/drivers/gpu/drm/i915/intel_panel.c +++ b/drivers/gpu/drm/i915/intel_panel.c @@ -576,11 +576,22 @@ void intel_panel_set_backlight(struct intel_connector *connector, u32 level, WARN_ON(panel->backlight.max == 0); - /* scale to hardware max, but be careful to not overflow */ - freq = panel->backlight.max; - n = (u64)level * freq; - do_div(n, max); - level = n; + /* XXX: we probably want to do this for all platforms. */ + if (IS_VALLEYVIEW(dev)) { + /* It's always safe to use vbt values for VLV since we fake them + * if they don't actually exist. */ + const int min_duty = (dev_priv->vbt.backlight.min_duty_cycle_percentage * + __vlv_calculate_mod_freq(dev_priv->vbt.backlight.pwm_freq_hz, true)) / 100; + BUG_ON(min_duty == 0); + /* linear conversion to new range */ +#define FIXED_POINT_SCALE 1000 + level = ((level * FIXED_POINT_SCALE / max) * (max - min_duty) / FIXED_POINT_SCALE) + min_duty; +#undef FIXED_POINT_SCALE + } else if (freq < max) + /* scale to hardware, but be careful to not overflow */ + level = level * freq / max; + else + level = freq / max * level; panel->backlight.level = level; if (panel->backlight.device) -- 1.7.9.5 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
