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

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: intel-gfx@lists.freedesktop.org, Lyude <cpaul@redhat.com>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	Hans de Goede <jwrdegoede@fedoraproject.org>,
	stable@vger.kernel.org
Subject: Re: [PATCH] drm/i915: Only enable hotplug interrupts if the display interrupts are enabled
Date: Wed, 15 Feb 2017 13:23:35 +0200	[thread overview]
Message-ID: <20170215112335.GR31595@intel.com> (raw)
In-Reply-To: <20170215090653.28740-1-chris@chris-wilson.co.uk>

On Wed, Feb 15, 2017 at 09:06:53AM +0000, Chris Wilson wrote:
> 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
> 
> 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 Syrjï¿½lï¿½ <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 Syrjï¿½lï¿½ <ville.syrjala@linux.intel.com>
> Cc: Hans de Goede <jwrdegoede@fedoraproject.org>
> Cc: stable@vger.kernel.org
> ---
>  drivers/gpu/drm/i915/intel_hotplug.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> 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)

I don't think we're setting display_irqs_enabled on any other platform
than VLV/CHV. So either we have to push this check down into
hpd_irq_setup() or just set display_irqs_enable=true somewhere for all
the other platforms.

>  		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

-- 
Ville Syrjï¿½lï¿½
Intel OTC