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Commit dce29156 authored by Ping Li's avatar Ping Li Committed by Gerrit - the friendly Code Review server
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msm: mdss: Optimize backlight mapping calculation for AD 



Reduce the rounding error during AD backlight linearization and
attenuation.

Change-Id: Ibf181414512d457d3341bbccf8cf9338aef8ac76
Signed-off-by: default avatarPing Li <pingli@codeaurora.org>
parent 863822f1

drivers/video/msm/mdss/mdss_mdp_pp.c

+23 −16
Original line number Diff line number Diff line 
/*

 * Copyright (c) 2012-2015, The Linux Foundation. All rights reserved.

 * Copyright (c) 2012-2016, The Linux Foundation. All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 and
@@ -5808,11 +5808,17 @@ static int pp_ad_attenuate_bl(struct mdss_ad_info *ad, u32 bl, u32 *bl_out) 
	u32 shift = 0, ratio_temp = 0;

	u32 n, lut_interval, bl_att;



	if (bl < 0) {

		pr_err("Invalid backlight input\n");

	if (bl < 0 || ad->init.alpha < 0) {

		pr_err("Invalid input: backlight = %d, alpha = %d\n", bl,

			ad->init.alpha);

		return -EINVAL;

	}



	if (ad->init.alpha == 0) {

		pr_debug("alpha = %d, hence no attenuation needed\n",

			ad->init.alpha);

		return 0;

	}

	pr_debug("bl_in = %d\n", bl);

	/* map panel backlight range to AD backlight range */

	linear_map(bl, &bl, ad->bl_mfd->panel_info->bl_max,
@@ -5835,12 +5841,9 @@ static int pp_ad_attenuate_bl(struct mdss_ad_info *ad, u32 bl, u32 *bl_out) 
		lut_interval;

	pr_debug("n = %u, bl_att_lut[%u] = %u, bl_att_lut[%u] = %u, bl_att = %u\n",

		n, n, ad->bl_att_lut[n], n + 1, ad->bl_att_lut[n + 1], bl_att);

	if (ad->init.alpha_base)

	*bl_out = (ad->init.alpha * bl_att +

		(ad->init.alpha_base - ad->init.alpha) * bl) /

		ad->init.alpha_base;

	else

		*bl_out = bl;



	pr_debug("After attenuation = %d\n", *bl_out);

	/* map AD backlight range back to panel backlight range */
@@ -5856,7 +5859,7 @@ static int pp_ad_linearize_bl(struct mdss_ad_info *ad, u32 bl, u32 *bl_out, 
	int inv)

{



	u32 n;

	u32 n, bl_lut_max_index = AD_BL_LIN_LEN - 1;

	uint32_t *bl_lut = NULL;

	int ret = -EINVAL;
@@ -5881,20 +5884,24 @@ static int pp_ad_linearize_bl(struct mdss_ad_info *ad, u32 bl, u32 *bl_out, 
		MDSS_MDP_AD_BL_SCALE);



	pr_debug("Before linearization = %d\n", bl);

	n = bl * (AD_BL_LIN_LEN - 1) / MDSS_MDP_AD_BL_SCALE;

	n = bl * bl_lut_max_index / MDSS_MDP_AD_BL_SCALE;

	pr_debug("n = %u\n", n);

	if (n > (AD_BL_LIN_LEN - 1)) {

	if (n > bl_lut_max_index) {

		pr_err("Invalid index for BL linearization: %d.\n", n);

		return ret;

	} else if (n == (AD_BL_LIN_LEN - 1)) {

	} else if (n == bl_lut_max_index) {

		*bl_out = bl_lut[n];

	} else if (bl == n * MDSS_MDP_AD_BL_SCALE / bl_lut_max_index) {

		*bl_out = bl_lut[n];

	} else if (bl == (n + 1) * MDSS_MDP_AD_BL_SCALE / bl_lut_max_index) {

		*bl_out = bl_lut[n + 1];

	} else {

		/* linear piece-wise interpolation */

		*bl_out = ((bl_lut[n + 1] - bl_lut[n]) *

			(bl - n * MDSS_MDP_AD_BL_SCALE /

			(AD_BL_LIN_LEN  - 1)) + bl_lut[n] *

			MDSS_MDP_AD_BL_SCALE / (AD_BL_LIN_LEN  - 1)) *

			(AD_BL_LIN_LEN  - 1) / MDSS_MDP_AD_BL_SCALE;

			bl_lut_max_index) + bl_lut[n] *

			MDSS_MDP_AD_BL_SCALE / bl_lut_max_index) *

			bl_lut_max_index / MDSS_MDP_AD_BL_SCALE;

	}

	pr_debug("After linearization = %d\n", *bl_out);