From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.16]) (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 E7C803BADB7; Fri, 22 May 2026 09:23:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.16 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779441796; cv=none; b=cNaBLCyBacFH4Znzwdq9ixYcEMUVSUayMvCGwQYATg3NiChR1QDdGrlgMtO+5m68FXpemH0mTBYTgYcMbuGKcEC58DKcbBiheclsfBiy0QH7ydoZg6WUUnku43WPNSALHGSdp9cG3BH0Y8aWl+Ng/546NkFRNCXJHM6ipA+J0Ws= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779441796; c=relaxed/simple; bh=zpUx7pgE7dGZ1EgENSHHQ/pITq/AWUQDi5Wy33xEqmA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZS36T7Y76XYM+z26dehx6HzRKIkUgLFaQTiZzMTswWMkpFq9ZumEiHkQwk2xX8MEV6OUAMZh6QnBip5nYZLgFUVNYQV9AN2DPd2Y4d77UxVVcTxoa6RMpd/gy3CXfBCly2FsZjwF8HOujjuS8u2bUi70twWULcsnuHbp7QSCrEg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=CXZQTs1Q; arc=none smtp.client-ip=198.175.65.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="CXZQTs1Q" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1779441795; x=1810977795; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=zpUx7pgE7dGZ1EgENSHHQ/pITq/AWUQDi5Wy33xEqmA=; b=CXZQTs1QY696dFdkMByzo3ATQdqwgM9Em6p3pdYfRBTFSQSPcrQve4rN auOIERSTvggYZj24+yeuwL+XLgnWr9vnug78wxTETmaAkhVniu0kXD0OS qk0WeEYgjjYRkekibye8iiSk7SLD4SxW4YGqzXMa086ZmwLnrZ7J52zh/ xXA2cU/WbWM00d/xzcr6DvWHx0zh5+wg/jXAHDlv+YqB76NzyRk62gLz4 OxKnDUtGfFUOQbnpzYHzfOjQqHDDdfP/okcM1Dy7NlPaCoI65LuI0MLc2 HTAni9Mf4eADZZgX3u25VAKrkDRVI06x6gKY8SluoYdLy3svaF4GIVNOf Q==; X-CSE-ConnectionGUID: sPYP0ierTNGhqCrA9Awm6A== X-CSE-MsgGUID: mEk8g2I+RAmNk6uwJy41hA== X-IronPort-AV: E=McAfee;i="6800,10657,11793"; a="80549990" X-IronPort-AV: E=Sophos;i="6.24,162,1774335600"; d="scan'208";a="80549990" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by orvoesa108.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 May 2026 02:23:14 -0700 X-CSE-ConnectionGUID: iJlfCes5T+GmhH3xgtuE/Q== X-CSE-MsgGUID: W1uz+iWWRj2reco7DY28hQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.24,162,1774335600"; d="scan'208";a="234512805" Received: from abityuts-desk.ger.corp.intel.com (HELO [10.245.244.203]) ([10.245.244.203]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 May 2026 02:23:12 -0700 Message-ID: <874533c1-716d-4c96-aa6f-87ab04c5f617@linux.intel.com> Date: Fri, 22 May 2026 11:23:03 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] drm/client: check whether CRTC is active before waiting for vblank To: Icenowy Zheng , Jani Nikula , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Sam Ravnborg Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260519092420.1124348-1-zhengxingda@iscas.ac.cn> <889a09d63c62d88a85d8a31a85feb8bbc178534c@intel.com> <7b49ae842c07a0437e6851aae944003785ef31a3.camel@icenowy.me> Content-Language: en-US From: Maarten Lankhorst In-Reply-To: <7b49ae842c07a0437e6851aae944003785ef31a3.camel@icenowy.me> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hey, Den 2026-05-19 kl. 13:29, skrev Icenowy Zheng: > 在 2026-05-19二的 12:41 +0300，Jani Nikula写道： >> On Tue, 19 May 2026, Icenowy Zheng wrote: >>> Currently the implementaion of drm_client_modeset_wait_for_vblank() >>> assumes drm_vblank_get() will fail when the CRTC isn't active. >>> However >>> it seems that this is not true, and running fbcon on a device with >>> the >>> first CRTC inactive will lead to kernel warning in some cases >>> (which >>> could be reproduced with the loongson driver). >>> >>> Change the implementation to add a check for the active state >>> (atomic) / >>> enabled state (non-atomic) before calling drm_vblank_get(). As the >>> assumption of drm_vblank_get() failing for inactive CRTC isn't met, >>> the >>> error status of drm_vblank_get() can now be exported too. >>> >>> Cc: stable@vger.kernel.org >>> Fixes: d8c4bddcd8bc ("drm/fb-helper: Synchronize dirty worker with >>> vblank") >>> Signed-off-by: Icenowy Zheng >>> --- >>>  drivers/gpu/drm/drm_client_modeset.c | 13 +++++++++++-- >>>  1 file changed, 11 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/drm_client_modeset.c >>> b/drivers/gpu/drm/drm_client_modeset.c >>> index bb49b8361271a..1b03bf351256e 100644 >>> --- a/drivers/gpu/drm/drm_client_modeset.c >>> +++ b/drivers/gpu/drm/drm_client_modeset.c >>> @@ -1310,7 +1310,7 @@ int drm_client_modeset_wait_for_vblank(struct >>> drm_client_dev *client, unsigned i >>>  { >>>   struct drm_device *dev = client->dev; >>>   struct drm_crtc *crtc; >>> - int ret; >>> + int ret = 0; >>>   >>>   /* >>>   * Rate-limit update frequency to vblank. If there's a DRM >>> master >>> @@ -1326,15 +1326,24 @@ int >>> drm_client_modeset_wait_for_vblank(struct drm_client_dev *client, >>> unsigned i >>>   * Only wait for a vblank event if the CRTC is enabled, >>> otherwise >>>   * just don't do anything, not even report an error. >>>   */ >> >> I'll dodge the question whether the change below is right or not, but >> for sure the comment above needs to be amended to match the change. > > If the change is right, it perfectly matches what the comment above is > saying -- it's the current behavior that does not match the comment. > > Thanks, > Icenowy I would rather have expected drm_fb_helper_ioctl to fail like you mention. Probably needs a fbcon_is_active() there to prevent it. The damage helper should not be triggered if no CRTC is active, so that means the check here is slightly too late. Can you fix it at a different level, like damage helper or its callers instead? I believe when the client gets suspended, all the pending damage is flushed before suspend. Kind regards, ~Maarten Lankhorst