drm/i915: Only enable hotplug interrupts if the display interrupts are enabled

In order to prevent accessing the hpd registers outside of the display
power wells, we should refrain from writing to the registers before the
display interrupts are enabled.

[    4.740136] WARNING: CPU: 1 PID: 221 at drivers/gpu/drm/i915/intel_uncore.c:795 __unclaimed_reg_debug+0x44/0x50 [i915]
[    4.740155] Unclaimed read from register 0x1e1110
[    4.740168] Modules linked in: i915(+) intel_gtt drm_kms_helper prime_numbers
[    4.740190] CPU: 1 PID: 221 Comm: systemd-udevd Not tainted 4.10.0-rc6+ torvalds#384
[    4.740203] Hardware name:                  /        , BIOS PYBSWCEL.86A.0027.2015.0507.1758 05/07/2015
[    4.740220] Call Trace:
[    4.740236]  dump_stack+0x4d/0x6f
[    4.740251]  __warn+0xc1/0xe0
[    4.740265]  warn_slowpath_fmt+0x4a/0x50
[    4.740281]  ? insert_work+0x77/0xc0
[    4.740355]  ? fwtable_write32+0x90/0x130 [i915]
[    4.740431]  __unclaimed_reg_debug+0x44/0x50 [i915]
[    4.740507]  fwtable_read32+0xd8/0x130 [i915]
[    4.740575]  i915_hpd_irq_setup+0xa5/0x100 [i915]
[    4.740649]  intel_hpd_init+0x68/0x80 [i915]
[    4.740716]  i915_driver_load+0xe19/0x1380 [i915]
[    4.740784]  i915_pci_probe+0x32/0x90 [i915]
[    4.740799]  pci_device_probe+0x8b/0xf0
[    4.740815]  driver_probe_device+0x2b6/0x450
[    4.740828]  __driver_attach+0xda/0xe0
[    4.740841]  ? driver_probe_device+0x450/0x450
[    4.740853]  bus_for_each_dev+0x5b/0x90
[    4.740865]  driver_attach+0x19/0x20
[    4.740878]  bus_add_driver+0x166/0x260
[    4.740892]  driver_register+0x5b/0xd0
[    4.740906]  ? 0xffffffffa0166000
[    4.740920]  __pci_register_driver+0x47/0x50
[    4.740985]  i915_init+0x5c/0x5e [i915]
[    4.740999]  do_one_initcall+0x3e/0x160
[    4.741015]  ? __vunmap+0x7c/0xc0
[    4.741029]  ? kmem_cache_alloc+0xcf/0x120
[    4.741045]  do_init_module+0x55/0x1c4
[    4.741060]  load_module+0x1f3f/0x25b0
[    4.741073]  ? __symbol_put+0x40/0x40
[    4.741086]  ? kernel_read_file+0x100/0x190
[    4.741100]  SYSC_finit_module+0xbc/0xf0
[    4.741112]  SyS_finit_module+0x9/0x10
[    4.741125]  entry_SYSCALL_64_fastpath+0x17/0x98
[    4.741135] RIP: 0033:0x7f8559a140f9
[    4.741145] RSP: 002b:00007fff7509a3e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
[    4.741161] RAX: ffffffffffffffda RBX: 00007f855aba02d1 RCX: 00007f8559a140f9
[    4.741172] RDX: 0000000000000000 RSI: 000055b6db0914f0 RDI: 0000000000000011
[    4.741183] RBP: 0000000000020000 R08: 0000000000000000 R09: 000000000000000e
[    4.741193] R10: 0000000000000011 R11: 0000000000000246 R12: 000055b6db0854d0
[    4.741204] R13: 000055b6db091150 R14: 0000000000000000 R15: 000055b6db035924

Fixes: 19625e8 ("drm/i915: Enable polling when we don't have hpd")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97798
Suggested-by: Ville Syrjälä <[email protected]>
Signed-off-by: Chris Wilson <[email protected]>
Cc: Lyude <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Ville Syrjälä <[email protected]>
Cc: Hans de Goede <[email protected]>
Cc: [email protected]

Author: ickle

drivers/gpu/drm/i915/intel_hotplug.c

@@ -219,7 +219,7 @@ static void intel_hpd_irq_storm_reenable_work(struct work_struct *work)
 			}
 		}
 	}
-	if (dev_priv->display.hpd_irq_setup)
+	if (dev_priv->display_irqs_enabled && dev_priv->display.hpd_irq_setup)
 		dev_priv->display.hpd_irq_setup(dev_priv);
 	spin_unlock_irq(&dev_priv->irq_lock);
 
@@ -425,7 +425,7 @@ void intel_hpd_irq_handler(struct drm_i915_private *dev_priv,
 		}
 	}
 
-	if (storm_detected)
+	if (storm_detected && dev_priv->display_irqs_enabled)
 		dev_priv->display.hpd_irq_setup(dev_priv);
 	spin_unlock(&dev_priv->irq_lock);
 
@@ -471,10 +471,11 @@ void intel_hpd_init(struct drm_i915_private *dev_priv)
 	 * Interrupt setup is already guaranteed to be single-threaded, this is
 	 * just to make the assert_spin_locked checks happy.
 	 */
-	spin_lock_irq(&dev_priv->irq_lock);
-	if (dev_priv->display.hpd_irq_setup)
+	if (dev_priv->display_irqs_enabled && dev_priv->display.hpd_irq_setup) {
+		spin_lock_irq(&dev_priv->irq_lock);
 		dev_priv->display.hpd_irq_setup(dev_priv);
-	spin_unlock_irq(&dev_priv->irq_lock);
+		spin_unlock_irq(&dev_priv->irq_lock);
+	}
 }
 
 static void i915_hpd_poll_init_work(struct work_struct *work)