From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 03A4B3B583B for ; Fri, 22 May 2026 13:24:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779456252; cv=none; b=FtOAu7krud5axA7zQA0rtYPxWXFOGPn23OZMOLDCTw9cNtwWw0TTQH3nZiipG3eXkMORDRRpXR0/0ptPOE0puAZ1uT/RcRtKFWrqJ3P+pyRrdnZmmJNSgQrOV66s3Vd504Qcvb4+jgOuyh/lkrtn0xhc9WAS3e0fO/c+Bwlvzyo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779456252; c=relaxed/simple; bh=9AoEHBE973Mhkv/GonKF+0W1+c27EELlYpey8q0W+8E=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=jxBKoOqMMfn2f3WR+9kt8/R/rjdNzdDn5Hx3PWaT2tTU0s5NHPRqC6jYl6t4iF4CqMLK7H3o4YRpN5036y2CIFDmAYfBlpZls3lJ3XonHCuwftflZCle03kz6KL2Fh7BW5KmlgJtmYVxNPUf2wbfRsL37yQ2MJ9Xz2xNmMLCpLI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de; spf=pass smtp.mailfrom=suse.de; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b=OT9XjWCb; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b=oTCD+481; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b=wcjtJpsR; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b=sKripMDz; arc=none smtp.client-ip=195.135.223.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b="OT9XjWCb"; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b="oTCD+481"; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b="wcjtJpsR"; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b="sKripMDz" Received: from imap1.dmz-prg2.suse.org (unknown [10.150.64.97]) (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) by smtp-out2.suse.de (Postfix) with ESMTPS id CF4C866E99; Fri, 22 May 2026 13:24:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1779456246; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=iZ+0ozTeC95GVs+zn1nU36tePjWc71LaXoy5Wu1qDZY=; b=OT9XjWCbOOI5MMAiFo+3Md6Tt1BUPOFCLxCN23TTBPO1MfJG1S6IT5AC63ztal7hKnUt3F MA0Wu8x9rysxe/SsQdAQ1GKzICAr7cAP9MHMd+ogdyRP25ESwBn7P1glFGgrg88/Ha8F5h 5eJMiSoR3OsbdXcwsoeK/LkSNtBEYjU= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1779456246; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=iZ+0ozTeC95GVs+zn1nU36tePjWc71LaXoy5Wu1qDZY=; b=oTCD+4814lWIUlRhDzd2RcxNkMsYsfGnRqRPWQoconmCet/tcclE5S4FcbcEVi6Ewf7fzq LgwmlMGMKiqPANCQ== Authentication-Results: smtp-out2.suse.de; none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1779456245; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=iZ+0ozTeC95GVs+zn1nU36tePjWc71LaXoy5Wu1qDZY=; b=wcjtJpsRlRanv4/JZokBVgfj9LpFqjAyzDHQs0VDZ9VwJXntdNKXm4IPxhNBVhtTj3Xqme JqRDBVQee8ws4UhhoI/niXsvgawOd8vmpDqX2D0ALVqXPP5MVoiWfnSOvA5ZcqECM7ZT8i hoUav1aAiha+arHB+k43PQF+67DmkEA= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1779456245; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=iZ+0ozTeC95GVs+zn1nU36tePjWc71LaXoy5Wu1qDZY=; b=sKripMDzRWw6fOseJDFgrA3JqU3VkZ9eaGqECb7N61BoTu9MKDlc15bUnHe+I/RyhpmPoF pEnxg5oZgexxxlAQ== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (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) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 82F48593A8; Fri, 22 May 2026 13:24:05 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id StNxHvVYEGp+LgAAD6G6ig (envelope-from ); Fri, 22 May 2026 13:24:05 +0000 Message-ID: Date: Fri, 22 May 2026 15:24:05 +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: =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= Cc: Icenowy Zheng , Maarten Lankhorst , Maxime Ripard , David Airlie , Simona Vetter , Sam Ravnborg , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Icenowy Zheng , stable@vger.kernel.org References: <20260519092420.1124348-1-zhengxingda@iscas.ac.cn> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; keydata= xsBNBFs50uABCADEHPidWt974CaxBVbrIBwqcq/WURinJ3+2WlIrKWspiP83vfZKaXhFYsdg XH47fDVbPPj+d6tQrw5lPQCyqjwrCPYnq3WlIBnGPJ4/jreTL6V+qfKRDlGLWFjZcsrPJGE0 BeB5BbqP5erN1qylK9i3gPoQjXGhpBpQYwRrEyQyjuvk+Ev0K1Jc5tVDeJAuau3TGNgah4Yc hdHm3bkPjz9EErV85RwvImQ1dptvx6s7xzwXTgGAsaYZsL8WCwDaTuqFa1d1jjlaxg6+tZsB 9GluwvIhSezPgnEmimZDkGnZRRSFiGP8yjqTjjWuf0bSj5rUnTGiyLyRZRNGcXmu6hjlABEB AAHNJ1Rob21hcyBaaW1tZXJtYW5uIDx0emltbWVybWFubkBzdXNlLmRlPsLAjgQTAQgAOAIb AwULCQgHAgYVCgkICwIEFgIDAQIeAQIXgBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftODH AAoJEGgNwR1TC3ojx1wH/0hKGWugiqDgLNXLRD/4TfHBEKmxIrmfu9Z5t7vwUKfwhFL6hqvo lXPJJKQpQ2z8+X2vZm/slsLn7J1yjrOsoJhKABDi+3QWWSGkaGwRJAdPVVyJMfJRNNNIKwVb U6B1BkX2XDKDGffF4TxlOpSQzdtNI/9gleOoUA8+jy8knnDYzjBNOZqLG2FuTdicBXblz0Mf vg41gd9kCwYXDnD91rJU8tzylXv03E75NCaTxTM+FBXPmsAVYQ4GYhhgFt8S2UWMoaaABLDe 7l5FdnLdDEcbmd8uLU2CaG4W2cLrUaI4jz2XbkcPQkqTQ3EB67hYkjiEE6Zy3ggOitiQGcqp j//OwE0EWznS4AEIAMYmP4M/V+T5RY5at/g7rUdNsLhWv1APYrh9RQefODYHrNRHUE9eosYb T6XMryR9hT8XlGOYRwKWwiQBoWSDiTMo/Xi29jUnn4BXfI2px2DTXwc22LKtLAgTRjP+qbU6 3Y0xnQN29UGDbYgyyK51DW3H0If2a3JNsheAAK+Xc9baj0LGIc8T9uiEWHBnCH+RdhgATnWW GKdDegUR5BkDfDg5O/FISymJBHx2Dyoklv5g4BzkgqTqwmaYzsl8UxZKvbaxq0zbehDda8lv hFXodNFMAgTLJlLuDYOGLK2AwbrS3Sp0AEbkpdJBb44qVlGm5bApZouHeJ/+n+7r12+lqdsA EQEAAcLAdgQYAQgAIAIbDBYhBHIX+6yM6c9jRKFo5WgNwR1TC3ojBQJftOH6AAoJEGgNwR1T C3ojVSkIALpAPkIJPQoURPb1VWjh34l0HlglmYHvZszJWTXYwavHR8+k6Baa6H7ufXNQtThR yIxJrQLW6rV5lm7TjhffEhxVCn37+cg0zZ3j7zIsSS0rx/aMwi6VhFJA5hfn3T0TtrijKP4A SAQO9xD1Zk9/61JWk8OysuIh7MXkl0fxbRKWE93XeQBhIJHQfnc+YBLprdnxR446Sh8Wn/2D Ya8cavuWf2zrB6cZurs048xe0UbSW5AOSo4V9M0jzYI4nZqTmPxYyXbm30Kvmz0rYVRaitYJ 4kyYYMhuULvrJDMjZRvaNe52tkKAvMevcGdt38H4KSVXAylqyQOW5zvPc4/sq9c= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Score: -4.30 X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_TLS_ALL(0.00)[]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_SEVEN(0.00)[11]; FUZZY_RATELIMITED(0.00)[rspamd.com]; MID_RHS_MATCH_FROM(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[iscas.ac.cn,linux.intel.com,kernel.org,gmail.com,ffwll.ch,ravnborg.org,lists.freedesktop.org,vger.kernel.org,icenowy.me]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,bootlin.com:url,suse.com:url,suse.de:mid] X-Spam-Level: X-Spam-Flag: NO Hi Am 22.05.26 um 15:13 schrieb Ville Syrjälä: > On Fri, May 22, 2026 at 01:55:59PM +0200, Thomas Zimmermann wrote: >> Hi >> >> Am 19.05.26 um 11:24 schrieb Icenowy Zheng: >>> 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. >>> */ >>> + if (drm_drv_uses_atomic_modeset(dev)) { >>> + if (!crtc->state || !crtc->state->active) >>> + goto out; >>> + } else { >>> + if (!crtc->enabled) >>> + goto out; >>> + } >>> + >> This part is good. > Locking is missing. Ok > >>> ret = drm_crtc_vblank_get(crtc); >>> if (!ret) { >>> drm_crtc_wait_one_vblank(crtc); >>> drm_crtc_vblank_put(crtc); >>> } >>> >>> +out: >>> drm_master_internal_release(dev); >>> >>> - return 0; >>> + return ret; >> But this isn't. There can be CRTCs without any vblank at all. We still >> want to fail silently for them. So we still have to return 0 here. >> >> Having set this, fixing this helper is only partially what you want. >> Since your device has vblanking, the emulation should check on the >> correct CRTC. IOW you need to pass the right CRTC index at >> >> https://elixir.bootlin.com/linux/v7.1-rc1/source/drivers/gpu/drm/drm_fb_helper.c#L237 >> https://elixir.bootlin.com/linux/v7.1-rc1/source/drivers/gpu/drm/drm_fb_helper.c#L920 >> >> I'm not quite sure how to support this. The CRTC is under >> fb_helper->client.modesets.crtc. You'd have to figure out which is the >> relevant one and use that. But that's also not so great, as fbdev ioctls >> only support CRTC 0. Doing internal re-mappings only complicates matters. >> >> But why does your HW use CRTC 1 in the first place. > Could be eg. the enabled outputs can't be driven with CRTC 0. > > I guess what you want to do is pick the first crtc from modesets[] > which is enabled. Or perhaps even "pick the Nth enabled crtc from > modesets[] based on the ioctl argument". The enable-status of each CRTC could change later on, which might lead to problems.  Picking the one CRTC/output with the lowest spec and mirroring it to the others might work. This CRTC would then be the one to wait for. Best regards Thomas > -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)