diff mbox

drm/i915: Avoid divbyzero in modesetting

Message ID 1456141948-7172-1-git-send-email-tvrtko.ursulin@linux.intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Tvrtko Ursulin Feb. 22, 2016, 11:52 a.m. UTC 
From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Not sure if intel_wm_config->num_pipes_active is supposed to
ever be zero when intel_update_watermarks gets called. But
since it can be triggered in early platform bringup perhaps
we want to guard against it rather than divide by zero.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

Comments

Maarten Lankhorst Feb. 22, 2016, 1:09 p.m. UTC | #1 
Hey,

Op 22-02-16 om 12:52 schreef Tvrtko Ursulin:
> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>
> Not sure if intel_wm_config->num_pipes_active is supposed to
> ever be zero when intel_update_watermarks gets called. But
> since it can be triggered in early platform bringup perhaps
> we want to guard against it rather than divide by zero.
>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Matt Roper <matthew.d.roper@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index feb57598727a..2b7998889617 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -2831,8 +2831,13 @@ skl_ddb_get_pipe_allocation_limits(struct drm_device *dev,
>  		nth_active_pipe++;
>  	}
>  
> -	pipe_size = ddb_size / config->num_pipes_active;
> -	alloc->start = nth_active_pipe * ddb_size / config->num_pipes_active;
> +	if (WARN_ON(!config->num_pipes_active)) {
> +		pipe_size = 0;
> +		alloc->start = 0;
> +	} else {
> +		pipe_size = ddb_size / config->num_pipes_active;
> +		alloc->start = nth_active_pipe * ddb_size / config->num_pipes_active;
> +	}
>  	alloc->end = alloc->start + pipe_size;
>  }
>  
How can this happen? It seems in that case cstate->base.active would be false for the current pipe,
and the code should bail early already..
Tvrtko Ursulin Feb. 22, 2016, 2:27 p.m. UTC | #2 
On 22/02/16 13:09, Maarten Lankhorst wrote:
> Hey,
> 
> Op 22-02-16 om 12:52 schreef Tvrtko Ursulin:
>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>
>> Not sure if intel_wm_config->num_pipes_active is supposed to
>> ever be zero when intel_update_watermarks gets called. But
>> since it can be triggered in early platform bringup perhaps
>> we want to guard against it rather than divide by zero.
>>
>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>> Cc: Matt Roper <matthew.d.roper@intel.com>
>> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
>> Cc: Daniel Vetter <daniel@ffwll.ch>
>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>> ---
>>   drivers/gpu/drm/i915/intel_pm.c | 9 +++++++--
>>   1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
>> index feb57598727a..2b7998889617 100644
>> --- a/drivers/gpu/drm/i915/intel_pm.c
>> +++ b/drivers/gpu/drm/i915/intel_pm.c
>> @@ -2831,8 +2831,13 @@ skl_ddb_get_pipe_allocation_limits(struct drm_device *dev,
>>   		nth_active_pipe++;
>>   	}
>>   
>> -	pipe_size = ddb_size / config->num_pipes_active;
>> -	alloc->start = nth_active_pipe * ddb_size / config->num_pipes_active;
>> +	if (WARN_ON(!config->num_pipes_active)) {
>> +		pipe_size = 0;
>> +		alloc->start = 0;
>> +	} else {
>> +		pipe_size = ddb_size / config->num_pipes_active;
>> +		alloc->start = nth_active_pipe * ddb_size / config->num_pipes_active;
>> +	}
>>   	alloc->end = alloc->start + pipe_size;
>>   }
>>   
> How can this happen? It seems in that case cstate->base.active would be false for the current pipe,
> and the code should bail early already..

Don't know, but does it harm to guard against it? Helps early
platform bringup a bit.

 [drm:intel_modeset_readout_hw_state] [CRTC:21] hw state readout: enabled
 [drm:intel_modeset_readout_hw_state] [CRTC:26] hw state readout: disabled
 [drm:intel_modeset_readout_hw_state] [CRTC:31] hw state readout: disabled
 [drm:intel_modeset_readout_hw_state] PORT PLL A hw state readout: crtc_mask 0x00000001, on 0
 [drm:intel_modeset_readout_hw_state] PORT PLL B hw state readout: crtc_mask 0x00000000, on 0
 [drm:intel_modeset_readout_hw_state] PORT PLL C hw state readout: crtc_mask 0x00000000, on 0
 [drm:intel_modeset_readout_hw_state] [ENCODER:33:TMDS-33] hw state readout: disabled, pipe A
 [drm:intel_modeset_readout_hw_state] [ENCODER:35:DP MST-35] hw state readout: disabled, pipe A
 [drm:intel_modeset_readout_hw_state] [ENCODER:36:DP MST-36] hw state readout: disabled, pipe B
 [drm:intel_modeset_readout_hw_state] [ENCODER:37:DP MST-37] hw state readout: disabled, pipe C
 [drm:intel_modeset_readout_hw_state] [ENCODER:42:TMDS-42] hw state readout: disabled, pipe A
 [drm:intel_modeset_readout_hw_state] [ENCODER:44:DP MST-44] hw state readout: disabled, pipe A
 [drm:intel_modeset_readout_hw_state] [ENCODER:45:DP MST-45] hw state readout: disabled, pipe B
 [drm:intel_modeset_readout_hw_state] [ENCODER:46:DP MST-46] hw state readout: disabled, pipe C
 [drm:intel_modeset_readout_hw_state] [CONNECTOR:34:DP-1] hw state readout: disabled
 [drm:intel_modeset_readout_hw_state] [CONNECTOR:40:HDMI-A-1] hw state readout: disabled
 [drm:intel_modeset_readout_hw_state] [CONNECTOR:43:DP-2] hw state readout: disabled
 [drm:intel_modeset_readout_hw_state] [CONNECTOR:47:HDMI-A-2] hw state readout: disabled
 [drm:drm_calc_timestamping_constants [drm]] *ERROR* crtc 21: Can't calculate constants, dotclock = 0!
 [drm:i915_get_vblank_timestamp] crtc 0 is disabled
 [drm:i915_get_vblank_timestamp] crtc 0 is disabled
 [drm:i915_get_vblank_timestamp] crtc 0 is disabled
 [drm:i915_get_vblank_timestamp] crtc 0 is disabled
 [drm:i915_get_vblank_timestamp] crtc 0 is disabled
 [drm:i915_get_vblank_timestamp] crtc 0 is disabled
 [drm:intel_disable_pipe] disabling pipe A

...

[   10.062881]  [<ffffffffa016add2>] skl_update_pipe_wm+0x102/0x8c0 [i915]
[   10.062942]  [<ffffffffa016b96f>] skl_update_wm+0xff/0x5f0 [i915]
[   10.063027]  [<ffffffffa016ce6e>] intel_update_watermarks+0x1e/0x30 [i915]
[   10.063087]  [<ffffffffa01d3ee2>] intel_crtc_disable_noatomic+0xd2/0x150 [i915]
[   10.063148]  [<ffffffffa01dd3d2>] intel_modeset_setup_hw_state+0xdd2/0xde0 [i915]
[   10.063181]  [<ffffffffa01dfd83>] intel_modeset_init+0x15a3/0x1950 [i915]
[   10.063181]  [<ffffffffa02160b6>] i915_driver_load+0x13c6/0x1720 [i915]

Regards,

Tvrtko
Maarten Lankhorst Feb. 23, 2016, 8:38 a.m. UTC | #3 
Op 22-02-16 om 15:27 schreef Tvrtko Ursulin:
> [   10.062881]  [<ffffffffa016add2>] skl_update_pipe_wm+0x102/0x8c0 [i915]
> [   10.062942]  [<ffffffffa016b96f>] skl_update_wm+0xff/0x5f0 [i915]
> [   10.063027]  [<ffffffffa016ce6e>] intel_update_watermarks+0x1e/0x30 [i915]
> [   10.063087]  [<ffffffffa01d3ee2>] intel_crtc_disable_noatomic+0xd2/0x150 [i915]
> [   10.063148]  [<ffffffffa01dd3d2>] intel_modeset_setup_hw_state+0xdd2/0xde0 [i915]
> [   10.063181]  [<ffffffffa01dfd83>] intel_modeset_init+0x15a3/0x1950 [i915]
> [   10.063181]  [<ffffffffa02160b6>] i915_driver_load+0x13c6/0x1720 [i915]
Do you have a full oops I can use for a commit description?
Tvrtko Ursulin Feb. 23, 2016, 9:49 a.m. UTC | #4 
On 23/02/16 08:38, Maarten Lankhorst wrote:
> Op 22-02-16 om 15:27 schreef Tvrtko Ursulin:
>> [   10.062881]  [<ffffffffa016add2>] skl_update_pipe_wm+0x102/0x8c0 [i915]
>> [   10.062942]  [<ffffffffa016b96f>] skl_update_wm+0xff/0x5f0 [i915]
>> [   10.063027]  [<ffffffffa016ce6e>] intel_update_watermarks+0x1e/0x30 [i915]
>> [   10.063087]  [<ffffffffa01d3ee2>] intel_crtc_disable_noatomic+0xd2/0x150 [i915]
>> [   10.063148]  [<ffffffffa01dd3d2>] intel_modeset_setup_hw_state+0xdd2/0xde0 [i915]
>> [   10.063181]  [<ffffffffa01dfd83>] intel_modeset_init+0x15a3/0x1950 [i915]
>> [   10.063181]  [<ffffffffa02160b6>] i915_driver_load+0x13c6/0x1720 [i915]
> Do you have a full oops I can use for a commit description?

Sure:

 ------------[ cut here ]------------
 WARNING: CPU: 1 PID: 295 at drivers/gpu/drm/i915/intel_pm.c:2834 skl_update_pipe_wm+0x102/0x8c0 [i915]()
 WARN_ON(!config->num_pipes_active)
 Modules linked in: coretemp i915(+) xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
 CPU: 1 PID: 295 Comm: systemd-udevd Tainted: G     U  W       4.5.0-rc4-xxxxxx #25
 Hardware name: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
  0000000000000000 ffff88003777f5a8 ffffffff813485c2 ffff88003777f5f0
  ffffffffa0236240 ffff88003777f5e0 ffffffff81050fce ffff8800aa420000
  ffff8800aba18000 ffff8800aba18000 ffff880037304c00 ffff8800aa420000
 Call Trace:
  [<ffffffff813485c2>] dump_stack+0x67/0x95
  [<ffffffff81050fce>] warn_slowpath_common+0x9e/0xc0
  [<ffffffff8105103c>] warn_slowpath_fmt+0x4c/0x50
  [<ffffffff8106945e>] ? flush_work+0x8e/0x280
  [<ffffffff810693d5>] ? flush_work+0x5/0x280
  [<ffffffffa016add2>] skl_update_pipe_wm+0x102/0x8c0 [i915]
  [<ffffffffa016b96f>] skl_update_wm+0xff/0x5f0 [i915]
  [<ffffffff810928ee>] ? trace_hardirqs_on_caller+0x15e/0x1d0
  [<ffffffff8109296d>] ? trace_hardirqs_on+0xd/0x10
  [<ffffffffa016ce6e>] intel_update_watermarks+0x1e/0x30 [i915]
  [<ffffffffa01d3ee2>] intel_crtc_disable_noatomic+0xd2/0x150 [i915]
  [<ffffffffa01dd3d2>] intel_modeset_setup_hw_state+0xdd2/0xde0 [i915]
  [<ffffffffa01dfd83>] intel_modeset_init+0x15a3/0x1950 [i915]
  [<ffffffffa02160b6>] i915_driver_load+0x13c6/0x1720 [i915]
  [<ffffffff81522160>] ? add_sysfs_fw_map_entry+0x9b/0x9b
  [<ffffffffa00b15ef>] drm_dev_register+0x6f/0xb0 [drm]
  [<ffffffffa00b3b3a>] drm_get_pci_dev+0x10a/0x1d0 [drm]
  [<ffffffffa01582d9>] i915_pci_probe+0x49/0x50 [i915]
  [<ffffffff8138ae30>] pci_device_probe+0x80/0xf0
  [<ffffffff8143e2ac>] driver_probe_device+0x1bc/0x3d0
  [<ffffffff8143e526>] __driver_attach+0x66/0x90
  [<ffffffff8143e4c0>] ? driver_probe_device+0x3d0/0x3d0
  [<ffffffff8143be3b>] bus_for_each_dev+0x5b/0xa0
  [<ffffffff8143db3e>] driver_attach+0x1e/0x20
  [<ffffffff8143d461>] bus_add_driver+0x151/0x270
  [<ffffffff8143eabc>] driver_register+0x8c/0xd0
  [<ffffffff8138a2ed>] __pci_register_driver+0x5d/0x60
  [<ffffffffa00b3c58>] drm_pci_init+0x58/0xf0 [drm]
  [<ffffffff8109296d>] ? trace_hardirqs_on+0xd/0x10
  [<ffffffffa02aa000>] ? 0xffffffffa02aa000
  [<ffffffffa02aa094>] i915_init+0x94/0x9b [i915]
  [<ffffffff81000423>] do_one_initcall+0x113/0x1f0
  [<ffffffff810a4b21>] ? rcu_read_lock_sched_held+0x61/0x90
  [<ffffffff811601dc>] ? kmem_cache_alloc_trace+0x1cc/0x280
  [<ffffffff8111110a>] do_init_module+0x60/0x1c8
  [<ffffffff810c731b>] load_module+0x1ceb/0x2410
  [<ffffffff810c3a60>] ? store_uevent+0x40/0x40
  [<ffffffff811763d1>] ? kernel_read+0x41/0x60
  [<ffffffff810c7c1d>] SYSC_finit_module+0x8d/0xa0
  [<ffffffff810c7c4e>] SyS_finit_module+0xe/0x10
  [<ffffffff815f1e97>] entry_SYSCALL_64_fastpath+0x12/0x6f
 ---[ end trace 1149e9ab3695a423 ]---
 ------------[ cut here ]------------

Regards,

Tvrtko
diff mbox

Patch

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index feb57598727a..2b7998889617 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -2831,8 +2831,13 @@  skl_ddb_get_pipe_allocation_limits(struct drm_device *dev,
 		nth_active_pipe++;
 	}
 
-	pipe_size = ddb_size / config->num_pipes_active;
-	alloc->start = nth_active_pipe * ddb_size / config->num_pipes_active;
+	if (WARN_ON(!config->num_pipes_active)) {
+		pipe_size = 0;
+		alloc->start = 0;
+	} else {
+		pipe_size = ddb_size / config->num_pipes_active;
+		alloc->start = nth_active_pipe * ddb_size / config->num_pipes_active;
+	}
 	alloc->end = alloc->start + pipe_size;
 }