[PATCH v2] drm/i915: Only enable hotplug interrupts if the display interrupts are enabled

[Chris Wilson <chris@chris-wilson.co.uk>]

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+ #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

v2: Set dev_priv->display_irqs_enabled to true for all platforms other
than vlv/chv that manually control the display power domain.

Fixes: 19625e85c6ec ("drm/i915: Enable polling when we don't have hpd")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97798
Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Lyude <cpaul@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Hans de Goede <jwrdegoede@fedoraproject.org>
Cc: stable@vger.kernel.org
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_irq.c      | 10 ++++++++++
 drivers/gpu/drm/i915/intel_hotplug.c | 11 ++++++-----
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index a887aeff4c73..91be31617e78 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -4284,6 +4284,16 @@ void intel_irq_init(struct drm_i915_private *dev_priv)
 	if (!IS_GEN2(dev_priv))
 		dev->vblank_disable_immediate = true;
 
+	/* Most platforms treat the display irq block as an always-on
+	 * power domain. vlv/chv can disable it at runtime and need
+	 * special care to avoid writing any of the display block registers
+	 * outside of the power domain. We defer setting up the display irqs
+	 * in this case to the runtime pm.
+	 */
+	dev_priv->display_irqs_enabled = true;
+	if (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv))
+		dev_priv->display_irqs_enabled = false;
+
 	dev_priv->hotplug.hpd_storm_threshold = HPD_STORM_DEFAULT_THRESHOLD;
 
 	dev->driver->get_vblank_timestamp = i915_get_vblank_timestamp;
diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
index 6a9c16508ab5..bad4f14858e3 100644
--- a/drivers/gpu/drm/i915/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/intel_hotplug.c
@@ -224,7 +224,7 @@ 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);
 
@@ -430,7 +430,7 @@ 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);
 
@@ -476,10 +476,11 @@ 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)
-- 
2.11.0