drm/panel/s6e3ha2: fix brightness to nits mapping

Brightness should be linearly mapped to nit values instead of nit indices.
Panel should use gamma index which has corresponding nit value nearest
to expected brightness after re-scaling.

Change-Id: I9bfa6385651b292881a10f8e2972551bdd0008de
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>

diff --git a/drivers/gpu/drm/panel/panel-s6e3ha2.c b/drivers/gpu/drm/panel/panel-s6e3ha2.c
index e0c2cb2..e919975 100644 (file)
--- a/drivers/gpu/drm/panel/panel-s6e3ha2.c
+++ b/drivers/gpu/drm/panel/panel-s6e3ha2.c
@@ -699,14 +699,31 @@ static void s6e3ha2_set_vint(struct s6e3ha2 *ctx)
        s6e3ha2_dcs_write_seq(ctx, 0xf4, 0x8b, VINT_TABLE[vind]);
 }
 
-static unsigned int s6e3ha2_get_brightness_index(unsigned int brightness)
+static unsigned int s6e3ha2_get_brightness_index(struct s6e3ha2 *ctx,
+       unsigned int brightness)
 {
-       return (brightness * (S6E3HA2_NITS_COUNT - 1)) / MAX_BRIGHTNESS;
+       int nit, b = 0, e = S6E3HA2_NITS_COUNT, m;
+       const int *nits = s6e3ha2_nits[ctx->model];
+
+       nit = brightness * nits[S6E3HA2_NITS_COUNT - 1] / MAX_BRIGHTNESS;
+
+       while (e - b > 1) {
+               m = (b + e) / 2;
+               if (nit < nits[m])
+                       e = m;
+               else
+                       b = m;
+       }
+
+       if (e < S6E3HA2_NITS_COUNT && nit - nits[b] > nits[e] - nit)
+               b = e;
+
+       return b;
 }
 
 static void s6e3ha2_update_gamma(struct s6e3ha2 *ctx, unsigned int brightness)
 {
-       unsigned int index = s6e3ha2_get_brightness_index(brightness);
+       unsigned int index = s6e3ha2_get_brightness_index(ctx, brightness);
        char data[DAID_PARAM_COUNT + 1];
 
        data[0] = LDI_GAMMODE1;