drm: adp: Handle drm_crtc_vblank_get() errors

drm_crtc_vblank_get() may fail when it's called before
drm_crtc_vblank_on() on a resetted CRTC. This occurs in
drm_crtc_helper_funcs' atomic_flush() calls after
drm_atomic_helper_crtc_reset() for example directly after probe.
Send the vblank event directly in such cases.
Avoids following warning in the subsequent drm_crtc_vblank_put() call
from the vblank irq handler as below:

adp 228200000.display-pipe: [drm] drm_WARN_ON(atomic_read(&vblank->refcount) == 0)
WARNING: CPU: 5 PID: 1206 at drivers/gpu/drm/drm_vblank.c:1247 drm_vblank_put+0x158/0x170
Modules linked in: uinput nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv6 nft_reject nft_ct nft_chain_nat nf_nat videodev drm_dma_helper mc apple_soc_cpufreq drm_display_helper leds_pwm phram
CPU: 5 UID: 0 PID: 1206 Comm: systemctl Not tainted 6.14.2-asahi+ #asahi-dev
Hardware name: Apple MacBook Pro (13-inch, M2, 2022) (DT)
pstate: 614000c5 (nZCv daIF +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
pc : drm_vblank_put+0x158/0x170
lr : drm_vblank_put+0x158/0x170
sp : ffffc00082aa7e70
x29: ffffc00082aa7e70 x28: ffff80003419e000 x27: ffff80003419e000
x26: 0000000000000001 x25: 0000000000012400 x24: 0000000000000066
x23: ffff800033fc8800 x22: 0000000000000000 x21: ffff800029688e70
x20: ffff800029688000 x19: ffff800029688000 x18: 0000000000000000
x17: ffffc0015c868000 x16: 0000000000000020 x15: 0000000000000004
x14: 0000000000000000 x13: 0000000000000001 x12: ffffc000825b3a90
x11: ffffc00082960e88 x10: ffffc00081b0ec88 x9 : ffffc0008017d0ec
x8 : 000000000002ffe8 x7 : fefefefefefefefe x6 : ffffc00081bbec88
x5 : ffff8001de237548 x4 : 0000000000000000 x3 : ffffc0015c868000
x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff80003419e000
Call trace:
 drm_vblank_put+0x158/0x170 (P)
 drm_crtc_vblank_put+0x24/0x38
 adp_fe_irq+0xd8/0xe8 [adpdrm]
 __handle_irq_event_percpu+0x94/0x318
 handle_irq_event+0x54/0xd0
 handle_fasteoi_irq+0xa8/0x240
 handle_irq_desc+0x3c/0x68
 generic_handle_domain_irq+0x24/0x40

Signed-off-by: Janne Grunau <j@jannau.net>

Author: jannau

drivers/gpu/drm/adp/adp_drv.c

@@ -331,13 +331,17 @@ static void adp_crtc_atomic_flush(struct drm_crtc *crtc,
 	}
 	writel(ADBE_FIFO_SYNC | frame_num, adp->be + ADBE_FIFO);
 	//FIXME: use adbe flush interrupt
-	spin_lock_irqsave(&crtc->dev->event_lock, flags);
 	if (crtc->state->event) {
-		drm_crtc_vblank_get(crtc);
-		adp->event = crtc->state->event;
+		spin_lock_irqsave(&crtc->dev->event_lock, flags);
+
+		if (drm_crtc_vblank_get(crtc) != 0)
+			drm_crtc_send_vblank_event(crtc, crtc->state->event);
+		else
+			adp->event = crtc->state->event;
+
+		spin_unlock_irqrestore(&crtc->dev->event_lock, flags);
 	}
 	crtc->state->event = NULL;
-	spin_unlock_irqrestore(&crtc->dev->event_lock, flags);
 }
 
 static const struct drm_crtc_funcs adp_crtc_funcs = {