From c38da578a86e62b1d585bae107651079cfa457ca Mon Sep 17 00:00:00 2001 From: Suraj Kandpal Date: Fri, 20 Jun 2025 12:04:38 +0530 Subject: [PATCH 4237/5403] drm/dp: Modify drm_edp_probe_state Modify drm_edp_probe_state to read current level from DP_EDP_PANEL_TARGET_LUMINANCE_VALUE. We divide it by 1000 since the value in this register is in millinits. --v2 -Add comment on the unit sent back [Arun] Signed-off-by: Suraj Kandpal Reviewed-by: Arun R Murthy Link: https://lore.kernel.org/r/20250620063445.3603086-7-suraj.kandpal@intel.com --- drivers/gpu/drm/display/drm_dp_helper.c | 40 ++++++++++++++++++------- 1 file changed, 30 insertions(+), 10 deletions(-) diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c index 374db5f85bfa..8a4fecf2fb91 100644 --- a/drivers/gpu/drm/display/drm_dp_helper.c +++ b/drivers/gpu/drm/display/drm_dp_helper.c @@ -4193,7 +4193,7 @@ drm_edp_backlight_probe_state(struct drm_dp_aux *aux, struct drm_edp_backlight_i u8 *current_mode) { int ret; - u8 buf[2]; + u8 buf[3]; u8 mode_reg; ret = drm_dp_dpcd_read_byte(aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER, &mode_reg); @@ -4210,17 +4210,37 @@ drm_edp_backlight_probe_state(struct drm_dp_aux *aux, struct drm_edp_backlight_i if (*current_mode == DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD) { int size = 1 + bl->lsb_reg_used; - ret = drm_dp_dpcd_read_data(aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB, buf, size); - if (ret < 0) { - drm_dbg_kms(aux->drm_dev, "%s: Failed to read backlight level: %d\n", - aux->name, ret); - return ret; + if (bl->luminance_set) { + ret = drm_dp_dpcd_read_data(aux, DP_EDP_PANEL_TARGET_LUMINANCE_VALUE, + buf, sizeof(buf)); + if (ret < 0) { + drm_dbg_kms(aux->drm_dev, + "%s: Failed to read backlight level: %d\n", + aux->name, ret); + return ret; } - if (bl->lsb_reg_used) - return (buf[0] << 8) | buf[1]; - else - return buf[0]; + /* + * Incase luminance is set we want to send the value back in nits but since + * DP_EDP_PANEL_TARGET_LUMINANCE stores values in millinits we need to divide + * by 1000. + */ + return (buf[0] | buf[1] << 8 | buf[2] << 16) / 1000; + } else { + ret = drm_dp_dpcd_read_data(aux, DP_EDP_BACKLIGHT_BRIGHTNESS_MSB, + buf, size); + if (ret < 0) { + drm_dbg_kms(aux->drm_dev, + "%s: Failed to read backlight level: %d\n", + aux->name, ret); + return ret; + } + + if (bl->lsb_reg_used) + return (buf[0] << 8) | buf[1]; + else + return buf[0]; + } } /* -- 2.54.0