From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 322923A9D92; Wed, 21 Jan 2026 18:33:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769020410; cv=none; b=MMXdUnE9GJZ7dUJObPZMH6HRePuZa5juXR7SMMEhyezpvG7tBYj7LG5WaUOWEswZUXba4w5I/f4RuxbFI/pFSA/o8gnFh6PagFGkmD9it1yDSioflF7An6ZiN/TcjUlkJh7xXYFAH6axVWj9PKrB9pVOFTOf+ySsWv4b1Lza+2Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769020410; c=relaxed/simple; bh=e/k1kMfRKP9+TZGmllYCbWX61r+oL5XnwIGFDu3/3pQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=aXfXDrdD5xm86uSlSNc8mfFJarEq6oYYzCFg18VgmydA/x9y/yJy2XuCsFYGTlg0F31QBnuUn3NHxjXEYdHN4GFOV3lf5rdPr5LPrxQgYVYElr6OXoeWdQy0sr/ZDBPRv5jrNBzGRgVQzAG6RsYvzN73N29FnJQi4xWBPt3ebb4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=g3lk9FaO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="g3lk9FaO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 80515C4CEF1; Wed, 21 Jan 2026 18:33:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1769020409; bh=e/k1kMfRKP9+TZGmllYCbWX61r+oL5XnwIGFDu3/3pQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=g3lk9FaOWyU3nnMQmsvLZztz36XYZnkh4CKIpD1eLaf0p6NJVL7+HNa9TuKICI+0W Vmbix5IVUzjYjBmMvrdTVXefbgwD5yPayDVxR7Iz0D45LEXqMnhat6PoMdXxN6Ul7x eceY4fKNDqWLknW5cc7z0IRO7F780bfop3Zymcok= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vivek Das Mohapatra , "Mario Limonciello (AMD)" , Alex Deucher Subject: [PATCH 6.18 150/198] drm/amd/display: Initialise backlight level values from hw Date: Wed, 21 Jan 2026 19:16:18 +0100 Message-ID: <20260121181423.955325773@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260121181418.537774329@linuxfoundation.org> References: <20260121181418.537774329@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vivek Das Mohapatra commit 52d3d115e9cc975b90b1fc49abf6d36ad5e8847a upstream. 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. Fixes: 2fe87f54abdc ("drm/amd/display: Set default brightness according to ACPI") Signed-off-by: Vivek Das Mohapatra Reviewed-by: Mario Limonciello (AMD) Signed-off-by: Alex Deucher (cherry picked from commit 318b1c36d82a0cd2b06a4bb43272fa6f1bc8adc1) Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -5193,6 +5193,8 @@ amdgpu_dm_register_backlight_device(stru 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; @@ -5217,6 +5219,8 @@ amdgpu_dm_register_backlight_device(stru } 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; @@ -5235,8 +5239,20 @@ amdgpu_dm_register_backlight_device(stru 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,