drm/i915/display: Make get_vblank_counter use intel_de_read_fw()

Fixes the following lockdep splat on PREEMPT_RT:
<3> BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
<3> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1373, name: xe_module_load
<3> preempt_count: 1, expected: 0
<3> RCU nest depth: 0, expected: 0
<4> 11 locks held by xe_module_load/1373:
<4>  #0: ffff888107b691a0 (&dev->mutex){....}-{3:3}, at: __driver_attach+0x104/0x220
<4>  #1: ffff88813cd30280 (&dev->clientlist_mutex){+.+.}-{3:3}, at: drm_client_register+0x32/0xe0
<4>  #2: ffffffff837f88f8 (registration_lock){+.+.}-{3:3}, at: register_framebuffer+0x1b/0x50
<4>  #3: ffffffff835985e0 (console_lock){+.+.}-{0:0}, at: fbcon_fb_registered+0x6f/0x90
<4>  #4: ffff88812589e6a0 (&helper->lock){+.+.}-{3:3}, at: __drm_fb_helper_restore_fbdev_mode_unlocked+0x7b/0x110
<4>  #5: ffff88813cd30158 (&dev->master_mutex){+.+.}-{3:3}, at: drm_master_internal_acquire+0x20/0x50
<4>  torvalds#6: ffff88812589e488 (&client->modeset_mutex){+.+.}-{3:3}, at: drm_client_modeset_commit_locked+0x2a/0x1b0
<4>  torvalds#7: ffffc9000031eef0 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_client_modeset_commit_atomic+0x4c/0x2b0
<4>  torvalds#8: ffffc9000031ef18 (crtc_ww_class_mutex){+.+.}-{3:3}, at: drm_client_modeset_commit_atomic+0x4c/0x2b0
<4>  torvalds#9: ffff888114f7b8b8 (&intel_dp->psr.lock){+.+.}-{3:3}, at: intel_psr_lock+0xc5/0xf0 [xe]
<4>  torvalds#10: ffff88812a0cbbc0 (&wl->lock){+.+.}-{2:2}, at: intel_dmc_wl_get+0x3c/0x140 [xe]

This splat will happen otherwise on all tracepoints too, for similar reasons.

Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>

Author: Maarten Lankhorst

drivers/gpu/drm/i915/display/intel_vblank.c

@@ -132,7 +132,7 @@ u32 g4x_get_vblank_counter(struct drm_crtc *crtc)
 	if (!vblank->max_vblank_count)
 		return 0;
 
-	return intel_de_read(display, PIPE_FRMCOUNT_G4X(display, pipe));
+	return intel_de_read_fw(display, PIPE_FRMCOUNT_G4X(display, pipe));
 }
 
 static u32 intel_crtc_scanlines_since_frame_timestamp(struct intel_crtc *crtc)