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bh=hQeVmqzuDx8T11tzAp4//+RKapBPir1cG8RoUEQn4Q4=; b=eYnjU2tjuUELLGYgMcsFCoSKutSJLdjYpvi33BPxaDPbv7sw6ZbXeH8a5B4FEyFqmG3kl+ TPfL0ubHD/8KDTCQ== 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 685CB13964; Tue, 10 Jun 2025 15:36:32 +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 M7QfGABRSGihUQAAD6G6ig (envelope-from ); Tue, 10 Jun 2025 15:36:32 +0000 Message-ID: <48f5a294-ab53-4cad-bb92-e1a90ee41fd0@suse.de> Date: Tue, 10 Jun 2025 17:36:31 +0200 Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/6] drm/vblank: Add vblank timer To: Louis Chauvet , mhklinux@outlook.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, airlied@gmail.com, simona@ffwll.ch, drawat.floss@gmail.com, javierm@redhat.com, kraxel@redhat.com, hamohammed.sa@gmail.com, melissa.srw@gmail.com, fvogt@suse.com Cc: dri-devel@lists.freedesktop.org, linux-hyperv@vger.kernel.org, virtualization@lists.linux.dev References: <20250605152637.98493-1-tzimmermann@suse.de> <20250605152637.98493-2-tzimmermann@suse.de> Content-Language: en-US From: Thomas Zimmermann Autocrypt: addr=tzimmermann@suse.de; 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RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; TAGGED_RCPT(0.00)[]; TO_DN_SOME(0.00)[] X-Spam-Level: X-Spam-Flag: NO X-Rspamd-Queue-Id: D22B6210F3 X-Rspamd-Action: no action X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Score: -3.01 Hi Am 06.06.25 um 10:43 schrieb Louis Chauvet: > > > Le 05/06/2025 à 17:24, Thomas Zimmermann a écrit : >> The vblank timer simulates a vblank interrupt for hardware without >> support. Rate-limits the display update frequency. >> >> DRM drivers for hardware without vblank support apply display updates >> ASAP. A vblank event informs DRM clients of the completed update. >> >> Userspace compositors immediately schedule the next update, which >> creates significant load on virtualization outputs. Display updates >> are usually fast on virtualization outputs, as their framebuffers are >> in regular system memory and there's no hardware vblank interrupt to >> throttle the update rate. >> >> The vblank timer is a HR timer that signals the vblank in software. >> It limits the update frequency of a DRM driver similar to a hardware >> vblank interrupt. The timer is not synchronized to the actual vblank >> interval of the display. >> >> The code has been adopted from vkms, which added the funtionality >> in commit 3a0709928b17 ("drm/vkms: Add vblank events simulated by >> hrtimers"). >> >> Signed-off-by: Thomas Zimmermann > > Tested-by: Louis Chauvet > Reviewed-by: Louis Chauvet Thanks for looking through the series. I'll add the tags when I prepare the next iteration, but the interfaces will change quite a bit. You may want to take another look at the series then. Best regards Thomas > >> --- >>   drivers/gpu/drm/Makefile           |   3 +- >>   drivers/gpu/drm/drm_vblank_timer.c | 100 +++++++++++++++++++++++++++++ >>   include/drm/drm_vblank_timer.h     |  26 ++++++++ >>   3 files changed, 128 insertions(+), 1 deletion(-) >>   create mode 100644 drivers/gpu/drm/drm_vblank_timer.c >>   create mode 100644 include/drm/drm_vblank_timer.h >> >> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile >> index b5d5561bbe5f..6722e2d1aa7e 100644 >> --- a/drivers/gpu/drm/Makefile >> +++ b/drivers/gpu/drm/Makefile >> @@ -146,7 +146,8 @@ drm_kms_helper-y := \ >>       drm_plane_helper.o \ >>       drm_probe_helper.o \ >>       drm_self_refresh_helper.o \ >> -    drm_simple_kms_helper.o >> +    drm_simple_kms_helper.o \ >> +    drm_vblank_timer.o >>   drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o >>   drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o >>   obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o >> diff --git a/drivers/gpu/drm/drm_vblank_timer.c >> b/drivers/gpu/drm/drm_vblank_timer.c >> new file mode 100644 >> index 000000000000..be46d3135c8e >> --- /dev/null >> +++ b/drivers/gpu/drm/drm_vblank_timer.c >> @@ -0,0 +1,100 @@ >> +// SPDX-License-Identifier: GPL-2.0+ >> + >> +#include >> + >> +#include >> +#include >> +#include >> +#include >> +#include >> + >> +static enum hrtimer_restart drm_vblank_timer_function(struct hrtimer >> *timer) >> +{ >> +    struct drm_vblank_timer *vtimer = container_of(timer, struct >> drm_vblank_timer, timer); >> +    struct drm_crtc *crtc = vtimer->crtc; >> +    struct drm_device *dev = crtc->dev; >> +    u64 ret_overrun; >> +    bool succ; >> + >> +    ret_overrun = hrtimer_forward_now(&vtimer->timer, >> vtimer->period_ns); >> +    if (ret_overrun != 1) >> +        drm_warn(dev, "vblank timer overrun\n"); >> + >> +    if (vtimer->crtc_handle_vblank) >> +        succ = vtimer->crtc_handle_vblank(crtc); >> +    else >> +        succ = drm_crtc_handle_vblank(crtc); >> +    if (!succ) >> +        return HRTIMER_NORESTART; >> + >> +    return HRTIMER_RESTART; >> +} >> + >> +static void drmm_vblank_timer_release(struct drm_device *dev, void >> *res) >> +{ >> +    struct drm_vblank_timer *vtimer = res; >> + >> +    hrtimer_cancel(&vtimer->timer); >> +} >> + >> +int drmm_vblank_timer_init(struct drm_vblank_timer *vtimer, struct >> drm_crtc *crtc, >> +               bool (*crtc_handle_vblank)(struct drm_crtc *crtc)) >> +{ >> +    struct hrtimer *timer = &vtimer->timer; >> + >> +    vtimer->crtc = crtc; >> +    vtimer->crtc_handle_vblank = crtc_handle_vblank; >> + >> +    hrtimer_setup(timer, drm_vblank_timer_function, CLOCK_MONOTONIC, >> HRTIMER_MODE_REL); >> + >> +    return drmm_add_action_or_reset(crtc->dev, >> drmm_vblank_timer_release, vtimer); >> +} >> +EXPORT_SYMBOL(drmm_vblank_timer_init); >> + >> +void drm_vblank_timer_start(struct drm_vblank_timer *vtimer) >> +{ >> +    struct drm_crtc *crtc = vtimer->crtc; >> +    struct drm_vblank_crtc *vblank = drm_crtc_vblank_crtc(crtc); >> + >> +    drm_calc_timestamping_constants(crtc, &crtc->mode); >> + >> +    vtimer->period_ns = ktime_set(0, vblank->framedur_ns); >> +    hrtimer_start(&vtimer->timer, vtimer->period_ns, HRTIMER_MODE_REL); >> +} >> +EXPORT_SYMBOL(drm_vblank_timer_start); >> + >> +void drm_vblank_timer_cancel(struct drm_vblank_timer *vtimer) >> +{ >> +    hrtimer_cancel(&vtimer->timer); >> +} >> +EXPORT_SYMBOL(drm_vblank_timer_cancel); >> + >> +bool drm_vblank_timer_get_vblank_timestamp(struct drm_vblank_timer >> *vtimer, >> +                       int *max_error, ktime_t *vblank_time, >> +                       bool in_vblank_irq) >> +{ >> +    struct drm_crtc *crtc = vtimer->crtc; >> +    struct drm_vblank_crtc *vblank = drm_crtc_vblank_crtc(crtc); >> + >> +    if (!READ_ONCE(vblank->enabled)) { >> +        *vblank_time = ktime_get(); >> +        return true; >> +    } >> + >> +    *vblank_time = READ_ONCE(vtimer->timer.node.expires); >> + >> +    if (WARN_ON(*vblank_time == vblank->time)) >> +        return true; >> + >> +    /* >> +     * To prevent races we roll the hrtimer forward before we do any >> +     * interrupt processing - this is how real hw works (the >> interrupt is >> +     * only generated after all the vblank registers are updated) >> and what >> +     * the vblank core expects. Therefore we need to always correct the >> +     * timestampe by one frame. >> +     */ >> +    *vblank_time -= vtimer->period_ns; >> + >> +    return true; >> +} >> +EXPORT_SYMBOL(drm_vblank_timer_get_vblank_timestamp); >> diff --git a/include/drm/drm_vblank_timer.h >> b/include/drm/drm_vblank_timer.h >> new file mode 100644 >> index 000000000000..0b827ff1f59c >> --- /dev/null >> +++ b/include/drm/drm_vblank_timer.h >> @@ -0,0 +1,26 @@ >> +/* SPDX-License-Identifier: GPL-2.0+ */ >> + >> +#ifndef _DRM_VBLANK_TIMER_H_ >> +#define _DRM_VBLANK_TIMER_H_ >> + >> +#include >> +#include >> + >> +struct drm_crtc; >> + >> +struct drm_vblank_timer { >> +    struct drm_crtc *crtc; >> +    bool (*crtc_handle_vblank)(struct drm_crtc *crtc); >> +    ktime_t period_ns; >> +    struct hrtimer timer; >> +}; >> + >> +int drmm_vblank_timer_init(struct drm_vblank_timer *vtimer, struct >> drm_crtc *crtc, >> +               bool (*handle_vblank)(struct drm_crtc *crtc)); >> +void drm_vblank_timer_start(struct drm_vblank_timer *vtimer); >> +void drm_vblank_timer_cancel(struct drm_vblank_timer *vtimer); >> +bool drm_vblank_timer_get_vblank_timestamp(struct drm_vblank_timer >> *vtimer, >> +                       int *max_error, ktime_t *vblank_time, >> +                       bool in_vblank_irq); >> + >> +#endif > -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)