Re: [Intel-gfx] [PATCH 2/5] drm/i915: Do not read GAMMA_MODE register

[Matt Roper <matthew.d.roper@intel.com>]

On Mon, Feb 22, 2016 at 02:18:08PM +0000, Lionel Landwerlin wrote:
> Implement Daniel Stone's recommendation to not read registers to infer
> the hardware's state.
> 
> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>

Do we need to ensure that software and hardware state are synchronized
at startup?  A boot firmware might have set it to something different
before our driver starts up; if we use 'fastboot' then we might not do
any modesets and might wind up with 0 (8BIT) in our state variable, but
something else actually programmed into the hardware.


Matt

> ---
>  drivers/gpu/drm/i915/intel_color.c | 7 +++++--
>  drivers/gpu/drm/i915/intel_drv.h   | 3 +++
>  2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_color.c b/drivers/gpu/drm/i915/intel_color.c
> index cce0155..ba27ce2 100644
> --- a/drivers/gpu/drm/i915/intel_color.c
> +++ b/drivers/gpu/drm/i915/intel_color.c
> @@ -126,6 +126,8 @@ static void haswell_load_luts(struct drm_crtc *crtc)
>  	struct drm_device *dev = crtc->dev;
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
> +	struct intel_crtc_state *intel_crtc_state =
> +		to_intel_crtc_state(crtc->state);
>  	bool reenable_ips = false;
>  
>  	/*
> @@ -133,11 +135,12 @@ static void haswell_load_luts(struct drm_crtc *crtc)
>  	 * GAMMA_MODE is configured for split gamma and IPS_CTL has IPS enabled.
>  	 */
>  	if (IS_HASWELL(dev) && intel_crtc->config->ips_enabled &&
> -	    ((I915_READ(GAMMA_MODE(intel_crtc->pipe)) & GAMMA_MODE_MODE_MASK) ==
> -	     GAMMA_MODE_MODE_SPLIT)) {
> +	    (intel_crtc_state->gamma_mode == GAMMA_MODE_MODE_SPLIT)) {
>  		hsw_disable_ips(intel_crtc);
>  		reenable_ips = true;
>  	}
> +
> +	intel_crtc_state->gamma_mode = GAMMA_MODE_MODE_8BIT;
>  	I915_WRITE(GAMMA_MODE(intel_crtc->pipe), GAMMA_MODE_MODE_8BIT);
>  
>  	i9xx_load_luts(crtc);
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 40fc486..9742d5b 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -517,6 +517,9 @@ struct intel_crtc_state {
>  			struct skl_pipe_wm skl;
>  		} optimal;
>  	} wm;
> +
> +	/* Gamma mode programmed on the pipe */
> +	uint32_t gamma_mode;
>  };
>  
>  struct vlv_wm_state {
> -- 
> 2.7.0
> 
> _______________________________________________
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> Intel-gfx@lists.freedesktop.org
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-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795
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