Re: [Intel-gfx] [PATCH v3 2/3] drm/amdgpu_dm: Rely on split out luminance calculation function

From: Jani Nikula <jani.nikula@intel.com>
To: "Jouni Högander" <jouni.hogander@intel.com>,
	dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
	amd-gfx@lists.freedesktop.org
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>,
	Roman Li <roman.li@amd.com>,
	Harry Wentland <harry.wentland@amd.com>
Subject: Re: [Intel-gfx] [PATCH v3 2/3] drm/amdgpu_dm: Rely on split out luminance calculation function
Date: Thu, 04 Aug 2022 12:54:42 +0300	[thread overview]
Message-ID: <877d3opc4d.fsf@intel.com> (raw)
In-Reply-To: <20220719095700.14923-3-jouni.hogander@intel.com>

On Tue, 19 Jul 2022, Jouni Högander <jouni.hogander@intel.com> wrote:
> Luminance range calculation was split out into drm_edid.c and is now
> part of edid parsing. Rely on values calculated during edid parsing and
> use these for caps->aux_max_input_signal and caps->aux_min_input_signal.

Harry, I'll merge patches 1 & 3 in this series through drm-misc-next,
because I think they're good to go, and fix stuff in i915.

Can I get your rb/ack to merge this patch as well, or do you want to
take this later via your tree?

BR,
Jani.

>
> v2: Use values calculated during edid parsing
>
> Cc: Roman Li <roman.li@amd.com>
> Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
> Cc: Harry Wentland <harry.wentland@amd.com>
> Cc: Lyude Paul <lyude@redhat.com>
> Cc: Mika Kahola <mika.kahola@intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
> ---
>  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 35 +++----------------
>  1 file changed, 4 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 3e83fed540e8..eb7abdeb8653 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -2903,15 +2903,12 @@ static struct drm_mode_config_helper_funcs amdgpu_dm_mode_config_helperfuncs = {
>  
>  static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector)
>  {
> -	u32 max_avg, min_cll, max, min, q, r;
>  	struct amdgpu_dm_backlight_caps *caps;
>  	struct amdgpu_display_manager *dm;
>  	struct drm_connector *conn_base;
>  	struct amdgpu_device *adev;
>  	struct dc_link *link = NULL;
> -	static const u8 pre_computed_values[] = {
> -		50, 51, 52, 53, 55, 56, 57, 58, 59, 61, 62, 63, 65, 66, 68, 69,
> -		71, 72, 74, 75, 77, 79, 81, 82, 84, 86, 88, 90, 92, 94, 96, 98};
> +	struct drm_luminance_range_info *luminance_range;
>  	int i;
>  
>  	if (!aconnector || !aconnector->dc_link)
> @@ -2933,8 +2930,6 @@ static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector)
>  	caps = &dm->backlight_caps[i];
>  	caps->ext_caps = &aconnector->dc_link->dpcd_sink_ext_caps;
>  	caps->aux_support = false;
> -	max_avg = conn_base->hdr_sink_metadata.hdmi_type1.max_fall;
> -	min_cll = conn_base->hdr_sink_metadata.hdmi_type1.min_cll;
>  
>  	if (caps->ext_caps->bits.oled == 1 /*||
>  	    caps->ext_caps->bits.sdr_aux_backlight_control == 1 ||
> @@ -2946,31 +2941,9 @@ static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector)
>  	else if (amdgpu_backlight == 1)
>  		caps->aux_support = true;
>  
> -	/* From the specification (CTA-861-G), for calculating the maximum
> -	 * luminance we need to use:
> -	 *	Luminance = 50*2**(CV/32)
> -	 * Where CV is a one-byte value.
> -	 * For calculating this expression we may need float point precision;
> -	 * to avoid this complexity level, we take advantage that CV is divided
> -	 * by a constant. From the Euclids division algorithm, we know that CV
> -	 * can be written as: CV = 32*q + r. Next, we replace CV in the
> -	 * Luminance expression and get 50*(2**q)*(2**(r/32)), hence we just
> -	 * need to pre-compute the value of r/32. For pre-computing the values
> -	 * We just used the following Ruby line:
> -	 *	(0...32).each {|cv| puts (50*2**(cv/32.0)).round}
> -	 * The results of the above expressions can be verified at
> -	 * pre_computed_values.
> -	 */
> -	q = max_avg >> 5;
> -	r = max_avg % 32;
> -	max = (1 << q) * pre_computed_values[r];
> -
> -	// min luminance: maxLum * (CV/255)^2 / 100
> -	q = DIV_ROUND_CLOSEST(min_cll, 255);
> -	min = max * DIV_ROUND_CLOSEST((q * q), 100);
> -
> -	caps->aux_max_input_signal = max;
> -	caps->aux_min_input_signal = min;
> +	luminance_range = &conn_base->display_info.luminance_range;
> +	caps->aux_min_input_signal = luminance_range->min_luminance;
> +	caps->aux_max_input_signal = luminance_range->max_luminance;
>  }
>  
>  void amdgpu_dm_update_connector_after_detect(

-- 
Jani Nikula, Intel Open Source Graphics Center