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Tue, 26 May 2026 07:59:06 +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 3dmVKMpSFWouJgAAD6G6ig (envelope-from ); Tue, 26 May 2026 07:59:06 +0000 Message-ID: Date: Tue, 26 May 2026 09:59:06 +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> <5fbcda92-f6b0-4de2-89e5-ea43a6248b05@suse.de> 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-Spam-Level: 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)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCVD_TLS_ALL(0.00)[]; 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]; internal_greylist_whitelist(0.00)[10.150.64.97]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.com:url,suse.de:mid] X-Spam-Flag: NO Hi Am 22.05.26 um 21:39 schrieb Ville Syrjälä: > On Fri, May 22, 2026 at 03:43:26PM +0200, Thomas Zimmermann wrote: >> Hi >> >> Am 22.05.26 um 15:28 schrieb Ville Syrjälä: >> [...] >>>>>> 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. >>> Sound like a locking issue if someone is changing the configuration >>> at the same time we're trying to do the vblank wait here. >> I mean that the connected outputs could change at a later point or we >> could have multiple CRTCs in use. Today, someone in #intel-gfx reported >> a problem with panning if multiple CRTCs are in use. >> >> Therefore picking a CRTC freely could be a problem. Let's say we >> configure modes from one CRTC, but later wait/pan/flush with another >> CRTC. I would not trust this to work correctly. >> >> Hence, my suggestion is to select a primary CRTC during the fbdev >> client's probe and use it for all later operations until the next probe >> happens.  All other CRTCs would mirror the primary one. > Actual mirroring may not be possible due to different modes supported > on each output. The whole multi-output fbdev thing in the drm fb helper > is kind of a hack that's rather hard to make work 100% sensibly. I know, but we have to support it to some extent. The current mirroring logic at least works, except that it assumes CRTC 0 to be present. Best regards Thomas > > For the panning possibly the only sensible thing is to use the max of > hdisplay/vdisplay of all the crtcs as the xres/yres so it's clear > how much things can actually be panned. Oh and tiled displays (assuming > we would actually want the fbdev stuff to tile correctly) make the > situation even more complicated. I think the current support for tiled > displays in the fb helper is semi-busted. > >> Best regards >> Thomas >> >> >>>> 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) >>>> >> -- >> -- >> 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) >> -- -- 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)