Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933919AbcJMB5L (ORCPT ); Wed, 12 Oct 2016 21:57:11 -0400 Received: from regular1.263xmail.com ([211.150.99.130]:45851 "EHLO regular1.263xmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933475AbcJMB5C (ORCPT ); Wed, 12 Oct 2016 21:57:02 -0400 X-263anti-spam: KSV:0;BIG:0;ABS:1;DNS:0;ATT:0;SPF:S; X-MAIL-GRAY: 0 X-MAIL-DELIVERY: 1 X-KSVirus-check: 0 X-ABS-CHECKED: 1 X-SKE-CHECKED: 1 X-ADDR-CHECKED4: 1 X-RL-SENDER: mark.yao@rock-chips.com X-FST-TO: ville.syrjala@linux.intel.com X-SENDER-IP: 58.22.7.114 X-LOGIN-NAME: mark.yao@rock-chips.com X-UNIQUE-TAG: X-ATTACHMENT-NUM: 0 X-DNS-TYPE: 0 Subject: Re: Question: Re: [PATCH] drm/bridge: analogix: protect power when get_modes or detect To: Sean Paul References: <1476266442-29803-1-git-send-email-mark.yao@rock-chips.com> <57FE0EF5.7010207@rock-chips.com> Cc: David Airlie , Heiko Stuebner , dri-devel , Linux ARM Kernel , linux-rockchip@lists.infradead.org, Linux Kernel Mailing List , Inki Dae , Gustavo Padovan , =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= From: Mark yao Message-ID: <57FEE9E2.20505@rock-chips.com> Date: Thu, 13 Oct 2016 09:56:50 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4449 Lines: 135 On 2016年10月12日 22:51, Sean Paul wrote: > On Wed, Oct 12, 2016 at 6:22 AM, Mark yao wrote: >> I'm not familiar with the analogix driver, maybe use a power reference count >> would better then direct power on/off analogix_dp. >> >> Does anyone has the idea to protect detect and get_modes context? >> > I'm not sure a reference count is going to help here. The common > pattern is to call detect() followed by get_modes() and then modeset. > However, it's not guaranteed that any one of those functions will be > called after the other. So, if you leave things on after detect or > get_modes, you might be wasting power (or worse). > > I recently ran into this exact problem with a panel we're using. Check > out "0b8b059a7: drm/bridge: analogix_dp: Ensure the panel is properly > prepared/unprepared". Perhaps you can piggyback on that function to > add your pm_runtime and plat_data callbacks (since using dpms_mode > might be racey). > > Sean Hi Sean Thanks for your advice. I re-test the detect and get_modes, only use pm_runtime_get/put also can fix my problem. without plat_data callbacks can avoid race to dpms_mode. I had send v2 patch, you can review it. Thanks. > >> I found many other connector driver also direct access register on detect or >> get_modes, no problem for it? >> >> On 2016年10月12日 18:00, Mark Yao wrote: >> >> The drm callback ->detect and ->get_modes seems is not power safe, >> they may be called when device is power off, do register access on >> detect or get_modes will cause system die. >> >> Here is the path call ->detect before analogix_dp power on >> [] analogix_dp_detect+0x44/0xdc >> [] >> drm_helper_probe_single_connector_modes_merge_bits+0xe8/0x41c >> [] drm_helper_probe_single_connector_modes+0x10/0x18 >> [] drm_mode_getconnector+0xf4/0x304 >> [] drm_ioctl+0x23c/0x390 >> [] do_vfs_ioctl+0x4b8/0x58c >> [] SyS_ioctl+0x60/0x88 >> >> Cc: Inki Dae >> Cc: Sean Paul >> Cc: Gustavo Padovan >> Cc: "Ville Syrjälä" >> >> Signed-off-by: Mark Yao >> --- >> drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 28 >> ++++++++++++++++++++++ >> 1 file changed, 28 insertions(+) >> >> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c >> b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c >> index efac8ab..09dece2 100644 >> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c >> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c >> @@ -1062,6 +1062,13 @@ int analogix_dp_get_modes(struct drm_connector >> *connector) >> return 0; >> } >> >> + if (dp->dpms_mode != DRM_MODE_DPMS_ON) { >> + pm_runtime_get_sync(dp->dev); >> + >> + if (dp->plat_data->power_on) >> + dp->plat_data->power_on(dp->plat_data); >> + } >> + >> if (analogix_dp_handle_edid(dp) == 0) { >> drm_mode_connector_update_edid_property(&dp->connector, edid); >> num_modes += drm_add_edid_modes(&dp->connector, edid); >> @@ -1073,6 +1080,13 @@ int analogix_dp_get_modes(struct drm_connector >> *connector) >> if (dp->plat_data->get_modes) >> num_modes += dp->plat_data->get_modes(dp->plat_data, connector); >> >> + if (dp->dpms_mode != DRM_MODE_DPMS_ON) { >> + if (dp->plat_data->power_off) >> + dp->plat_data->power_off(dp->plat_data); >> + >> + pm_runtime_put_sync(dp->dev); >> + } >> + >> ret = analogix_dp_prepare_panel(dp, false, false); >> if (ret) >> DRM_ERROR("Failed to unprepare panel (%d)\n", ret); >> @@ -1106,9 +1120,23 @@ analogix_dp_detect(struct drm_connector *connector, >> bool force) >> return connector_status_disconnected; >> } >> >> + if (dp->dpms_mode != DRM_MODE_DPMS_ON) { >> + pm_runtime_get_sync(dp->dev); >> + >> + if (dp->plat_data->power_on) >> + dp->plat_data->power_on(dp->plat_data); >> + } >> + >> if (!analogix_dp_detect_hpd(dp)) >> status = connector_status_connected; >> >> + if (dp->dpms_mode != DRM_MODE_DPMS_ON) { >> + if (dp->plat_data->power_off) >> + dp->plat_data->power_off(dp->plat_data); >> + >> + pm_runtime_put_sync(dp->dev); >> + } >> + >> ret = analogix_dp_prepare_panel(dp, false, false); >> if (ret) >> DRM_ERROR("Failed to unprepare panel (%d)\n", ret); >> >> >> >> -- >> Ｍark Yao > > -- Ｍark Yao