On 11/14/2011 11:39 AM, Takashi Iwai wrote:
> OK, then perhaps a better fix is to change the check to be equivalent
> with pineview, as you mentioned in the original post. The handling of
> bit 0 for old chips was lost during the refactoring of backlight code
> since 2.6.37.
>
> Does the patch below work for you?
>
> The only concern by this fix is that it changes the max value. If
> apps expect some certain (e.g. recorded) value, it may screw up. But
> I don't expect this would happen with sane apps.
Works perfectly - let's ship it :)
Thanks again,
Daniel
> ===
> From: Takashi Iwai <tiwai@xxxxxxx>
> Subject: drm/i915: Fix invalid backpanel values for GEN3 or older chips
>
> While refactoring of backlight control code in commit [a95735569:
> drm/i915: Refactor panel backlight controls], the handling of the bit
> 0 of duty-cycle was gone except for pineview. This resulted in invalid
> register values for old chips like 915GM. When the bit 0 is set, the
> backlight is turned off suddenly.
>
> This patch changes the bit-0 check by replacing with the condition of
> gen < 4 (pineview is included in this condition, too).
>
> Reported-by: Daniel Mack <zonque@xxxxxxxxx>
> Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_panel.c | 8 +++-----
> 1 files changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 499d4c0..737d00f 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -178,12 +178,10 @@ u32 intel_panel_get_max_backlight(struct drm_device *dev)
> if (HAS_PCH_SPLIT(dev)) {
> max >>= 16;
> } else {
> - if (IS_PINEVIEW(dev)) {
> + if (INTEL_INFO(dev)->gen < 4) {
> max >>= 17;
> } else {
> max >>= 16;
> - if (INTEL_INFO(dev)->gen < 4)
> - max &= ~1;
> }
>
> if (is_backlight_combination_mode(dev))
> @@ -203,7 +201,7 @@ u32 intel_panel_get_backlight(struct drm_device *dev)
> val = I915_READ(BLC_PWM_CPU_CTL) & BACKLIGHT_DUTY_CYCLE_MASK;
> } else {
> val = I915_READ(BLC_PWM_CTL) & BACKLIGHT_DUTY_CYCLE_MASK;
> - if (IS_PINEVIEW(dev))
> + if (INTEL_INFO(dev)->gen < 4)
> val >>= 1;
>
> if (is_backlight_combination_mode(dev)) {
> @@ -246,7 +244,7 @@ static void intel_panel_actually_set_backlight(struct drm_device *dev, u32 level
> }
>
> tmp = I915_READ(BLC_PWM_CTL);
> - if (IS_PINEVIEW(dev)) {
> + if (INTEL_INFO(dev)->gen < 4) {
> tmp &= ~(BACKLIGHT_DUTY_CYCLE_MASK - 1);
> level <<= 1;
> } else
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