Re: [PATCH 1/4] drm/i915: save/restore the legacy backlight control

["Indan Zupancic" <indan@nul.nu>]

Hello,

On Tue, August 28, 2012 08:53, Jani Nikula wrote:
> From: Daniel Vetter <daniel.vetter@ffwll.ch>
>
> This is a prep patch to stop drm/i915 from changing the LBPC registers
> itself - but we still need to properly save/restore it on
> suspend/resume.
>
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h     |    1 +
>  drivers/gpu/drm/i915/i915_reg.h     |    3 +++
>  drivers/gpu/drm/i915/i915_suspend.c |    8 ++++++++
>  drivers/gpu/drm/i915/intel_panel.c  |    2 --
>  4 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 58b43db..af1701c 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -606,6 +606,7 @@ typedef struct drm_i915_private {
>  	u32 savePP_CONTROL;
>  	u32 savePP_DIVISOR;
>  	u32 savePFIT_CONTROL;
> +	u8 saveLBPC;
>  	u32 save_palette_a[256];
>  	u32 save_palette_b[256];
>  	u32 saveDPFC_CB_BASE;
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index d0b60f2..3303c18 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -1889,6 +1889,9 @@
>
>  #define PFIT_AUTO_RATIOS 0x61238
>
> +/* legacy/combination backlight modes in pci config space. */
> +#define PCI_LBPC 0xf4
> +
>  /* Backlight control */
>  #define BLC_PWM_CTL2		0x61250 /* 965+ only */
>  #define   BLM_PWM_ENABLE		(1 << 31)
> diff --git a/drivers/gpu/drm/i915/i915_suspend.c b/drivers/gpu/drm/i915/i915_suspend.c
> index 4776ccf..05daff7 100644
> --- a/drivers/gpu/drm/i915/i915_suspend.c
> +++ b/drivers/gpu/drm/i915/i915_suspend.c
> @@ -639,6 +639,10 @@ static void i915_save_display(struct drm_device *dev)
>  			dev_priv->saveBLC_PWM_CTL2 = I915_READ(BLC_PWM_CTL2);
>  		if (IS_MOBILE(dev) && !IS_I830(dev))
>  			dev_priv->saveLVDS = I915_READ(LVDS);
> +
> +		if (IS_GEN2(dev) || IS_GEN4(dev))
> +			pci_read_config_byte(dev->pdev, PCI_LBPC,
> +					     &dev_priv->saveLBPC);

What about GEN3?

It seems weird that LBPC wouldn't be restored during resume by some BIOSes,
is this really necessary?

Greetings,

Indan