From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 28010D29DE0 for ; Tue, 13 Jan 2026 08:02:45 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 21B1710E46D; Tue, 13 Jan 2026 08:02:40 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=collabora.com header.i=@collabora.com header.b="lpg9efCT"; dkim-atps=neutral Received: from bali.collaboradmins.com (bali.collaboradmins.com [148.251.105.195]) by gabe.freedesktop.org (Postfix) with ESMTPS id D0674890EB; Mon, 12 Jan 2026 15:29:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1768231741; bh=2EBOUlFdg3MszkEBGNlnfrYy2xczDbjzxVzmkBS+tt8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lpg9efCTjL9dEcFCNwqHaMJbX0lZhj+F9+dNTVXtFuT1nb0YzDRn8IIa2LqU85lwE xcZ/fg/UcpNjWs/DHM3prQFyQhpdYwLVYpKUDpHWgzAKBZwVMsGtNS2e+PbXBtokI8 GQtKXxQVh+/TYoAPM2+/Z/bT44afLkB0rtdDLDqYmhDhHII93Ttpv2tuCWZp07UNPm xVHKS+BGltaLFfs1JEu/qxmkW9zchhWn6lokjh67RixNh8nfqabSH0TYWzvj/pf3rP UZsgc2E36Hy6SMcv0ypJjNGAVn84pZVmtWGvyrRabqA/ucQyG10LHYqF1e3FTjr1k5 SpxLSw9a9vhAw== Received: from nemo.lan (unknown [IPv6:2a07:244:40:6b00::646]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: vivek) by bali.collaboradmins.com (Postfix) with ESMTPSA id E938917E13F1; Mon, 12 Jan 2026 16:29:00 +0100 (CET) From: Vivek Das Mohapatra To: superm1@kernel.org Cc: airlied@gmail.com, alexander.deucher@amd.com, amd-gfx@lists.freedesktop.org, christian.koenig@amd.com, dri-devel@lists.freedesktop.org, harry.wentland@amd.com, kernel@collabora.com, linux-kernel@vger.kernel.org, simona@ffwll.ch, siqueira@igalia.com, sunpeng.li@amd.com, vivek@collabora.com Subject: [PATCH v2] drm/amd/display: Initialise backlight level values from hw Date: Mon, 12 Jan 2026 15:28:56 +0000 Message-Id: <20260112152856.2616532-1-vivek@collabora.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <7ec7b4ae-6186-4961-a857-f97afcfc3ded@kernel.org> References: <7ec7b4ae-6186-4961-a857-f97afcfc3ded@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Mailman-Approved-At: Tue, 13 Jan 2026 08:02:37 +0000 X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" Internal backlight levels are initialised from ACPI but the values are sometimes out of sync with the levels in effect until there has been a read from hardware (eg triggered by reading from sysfs). This means that the first drm_commit can cause the levels to be set to a different value than the actual starting one, which results in a sudden change in brightness. This path shows the problem (when the values are out of sync): amdgpu_dm_atomic_commit_tail() -> amdgpu_dm_commit_streams() -> amdgpu_dm_backlight_set_level(..., dm->brightness[n]) This patch calls the backlight ops get_brightness explicitly at the end of backlight registration to make sure dm->brightness[n] is in sync with the actual hardware levels. Signed-off-by: Vivek Das Mohapatra --- .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) 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 354e359c4507..9e8cbfeee915 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -5258,6 +5258,8 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector) struct amdgpu_dm_backlight_caps *caps; char bl_name[16]; int min, max; + int real_brightness; + int init_brightness; if (aconnector->bl_idx == -1) return; @@ -5282,6 +5284,8 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector) } else props.brightness = props.max_brightness = MAX_BACKLIGHT_LEVEL; + init_brightness = props.brightness; + if (caps->data_points && !(amdgpu_dc_debug_mask & DC_DISABLE_CUSTOM_BRIGHTNESS_CURVE)) { drm_info(drm, "Using custom brightness curve\n"); props.scale = BACKLIGHT_SCALE_NON_LINEAR; @@ -5300,8 +5304,20 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector) if (IS_ERR(dm->backlight_dev[aconnector->bl_idx])) { drm_err(drm, "DM: Backlight registration failed!\n"); dm->backlight_dev[aconnector->bl_idx] = NULL; - } else + } else { + /* + * dm->brightness[x] can be inconsistent just after startup until + * ops.get_brightness is called. + */ + real_brightness = + amdgpu_dm_backlight_ops.get_brightness(dm->backlight_dev[aconnector->bl_idx]); + + if (real_brightness != init_brightness) { + dm->actual_brightness[aconnector->bl_idx] = real_brightness; + dm->brightness[aconnector->bl_idx] = real_brightness; + } drm_dbg_driver(drm, "DM: Registered Backlight device: %s\n", bl_name); + } } static int initialize_plane(struct amdgpu_display_manager *dm, -- 2.39.5