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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5A0AFC433FE for ; Mon, 24 Jan 2022 22:04:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1379636AbiAXWEP (ORCPT ); Mon, 24 Jan 2022 17:04:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51562 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1450889AbiAXVVn (ORCPT ); Mon, 24 Jan 2022 16:21:43 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9809BC0604E1; Mon, 24 Jan 2022 12:16:24 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 35A4C611CD; Mon, 24 Jan 2022 20:16:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F0DBCC340E5; Mon, 24 Jan 2022 20:16:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643055383; bh=Gj/ZBJfXwO4Vq/uUWw7uOBpKsabtffRUsI+FbzQkHyo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XYL3eOyhzNXhwQc6rpHK39Tjeq0jyLZ0mg15AECcrLlvHRIdXjYPIN+jErH4iWlty kOPtUpEDyYhx6fh0SyNwvND9YUS2vAb3L/j+5Q5MMnWMWrdqkTHc1gyDP58quzx3rq TSZCTHwHXhQbaPDpHLcMbzrYSUykd0pvYyayKLtw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Lyude Paul , Douglas Anderson , Sasha Levin Subject: [PATCH 5.15 133/846] drm/dp: Dont read back backlight mode in drm_edp_backlight_enable() Date: Mon, 24 Jan 2022 19:34:10 +0100 Message-Id: <20220124184105.572031601@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220124184100.867127425@linuxfoundation.org> References: <20220124184100.867127425@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lyude Paul [ Upstream commit 646596485e1ed2182adf293dfd5aec4a96c46330 ] As it turns out, apparently some machines will actually leave additional backlight functionality like dynamic backlight control on before the OS loads. Currently we don't take care to disable unsupported features when writing back the backlight mode, which can lead to some rather strange looking behavior when adjusting the backlight. So, let's fix this by just not reading back the current backlight mode on initial enable. I don't think there should really be any downsides to this, and this will ensure we don't leave any unsupported functionality enabled. This should fix at least one (but not all) of the issues seen with DPCD backlight support on fi-bdw-samus v5: * Just avoid reading back DPCD register - Doug Anderson Signed-off-by: Lyude Paul Fixes: 867cf9cd73c3 ("drm/dp: Extract i915's eDP backlight code into DRM helpers") Reviewed-by: Douglas Anderson Link: https://patchwork.freedesktop.org/patch/msgid/20211105183342.130810-4-lyude@redhat.com Signed-off-by: Sasha Levin --- drivers/gpu/drm/drm_dp_helper.c | 40 ++++++++++----------------------- 1 file changed, 12 insertions(+), 28 deletions(-) diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 6d0f2c447f3b9..7bb24523a7493 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -3214,27 +3214,13 @@ int drm_edp_backlight_enable(struct drm_dp_aux *aux, const struct drm_edp_backli const u16 level) { int ret; - u8 dpcd_buf, new_dpcd_buf; + u8 dpcd_buf = DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD; - ret = drm_dp_dpcd_readb(aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER, &dpcd_buf); - if (ret != 1) { - drm_dbg_kms(aux->drm_dev, - "%s: Failed to read backlight mode: %d\n", aux->name, ret); - return ret < 0 ? ret : -EIO; - } - - new_dpcd_buf = dpcd_buf; - - if ((dpcd_buf & DP_EDP_BACKLIGHT_CONTROL_MODE_MASK) != DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD) { - new_dpcd_buf &= ~DP_EDP_BACKLIGHT_CONTROL_MODE_MASK; - new_dpcd_buf |= DP_EDP_BACKLIGHT_CONTROL_MODE_DPCD; - - if (bl->pwmgen_bit_count) { - ret = drm_dp_dpcd_writeb(aux, DP_EDP_PWMGEN_BIT_COUNT, bl->pwmgen_bit_count); - if (ret != 1) - drm_dbg_kms(aux->drm_dev, "%s: Failed to write aux pwmgen bit count: %d\n", - aux->name, ret); - } + if (bl->pwmgen_bit_count) { + ret = drm_dp_dpcd_writeb(aux, DP_EDP_PWMGEN_BIT_COUNT, bl->pwmgen_bit_count); + if (ret != 1) + drm_dbg_kms(aux->drm_dev, "%s: Failed to write aux pwmgen bit count: %d\n", + aux->name, ret); } if (bl->pwm_freq_pre_divider) { @@ -3244,16 +3230,14 @@ int drm_edp_backlight_enable(struct drm_dp_aux *aux, const struct drm_edp_backli "%s: Failed to write aux backlight frequency: %d\n", aux->name, ret); else - new_dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE; + dpcd_buf |= DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE; } - if (new_dpcd_buf != dpcd_buf) { - ret = drm_dp_dpcd_writeb(aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER, new_dpcd_buf); - if (ret != 1) { - drm_dbg_kms(aux->drm_dev, "%s: Failed to write aux backlight mode: %d\n", - aux->name, ret); - return ret < 0 ? ret : -EIO; - } + ret = drm_dp_dpcd_writeb(aux, DP_EDP_BACKLIGHT_MODE_SET_REGISTER, dpcd_buf); + if (ret != 1) { + drm_dbg_kms(aux->drm_dev, "%s: Failed to write aux backlight mode: %d\n", + aux->name, ret); + return ret < 0 ? ret : -EIO; } ret = drm_edp_backlight_set_level(aux, bl, level); -- 2.34.1