[Intel-gfx] [PATCH] drm/i915: Avoid busy-spinning on VLV_GLTC_PW_STATUS mmio
Ville Syrjälä
ville.syrjala at linux.intel.com
Fri Apr 21 13:38:49 UTC 2017
On Fri, Apr 21, 2017 at 02:00:40PM +0100, Chris Wilson wrote:
> The busy-spin, as the first stage of intel_wait_for_register, is
> currently under suspicion for causing:
>
> [ 62.034926] NMI watchdog: Watchdog detected hard LOCKUP on cpu 1
> [ 62.034928] Modules linked in: i2c_dev i915 intel_gtt drm_kms_helper prime_numbers
> [ 62.034932] CPU: 1 PID: 183 Comm: kworker/1:2 Not tainted 4.11.0-rc7+ #471
> [ 62.034933] Hardware name: / , BIOS PYBSWCEL.86A.0027.2015.0507.1758 05/07/2015
> [ 62.034934] Workqueue: pm pm_runtime_work
> [ 62.034936] task: ffff880275a04ec0 task.stack: ffffc900002d8000
> [ 62.034936] RIP: 0010:__intel_wait_for_register_fw+0x77/0x1a0 [i915]
> [ 62.034937] RSP: 0018:ffffc900002dbc38 EFLAGS: 00000082
> [ 62.034939] RAX: ffffc90003530094 RBX: 0000000000130094 RCX: 0000000000000001
> [ 62.034940] RDX: 00000000000000a1 RSI: ffff88027fd15e58 RDI: 0000000000000000
> [ 62.034941] RBP: ffffc900002dbc78 R08: 0000000000000002 R09: 0000000000000000
> [ 62.034942] R10: ffffc900002dbc18 R11: ffff880276429dd0 R12: ffff8802707c0000
> [ 62.034943] R13: 00000000000000a0 R14: 0000000000000000 R15: 00000000fffefc10
> [ 62.034945] FS: 0000000000000000(0000) GS:ffff88027fd00000(0000) knlGS:0000000000000000
> [ 62.034945] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 62.034947] CR2: 00007ffd3cd98ff8 CR3: 0000000274c19000 CR4: 00000000001006e0
> [ 62.034947] Call Trace:
> [ 62.034948] intel_wait_for_register+0x77/0x140 [i915]
> [ 62.034949] vlv_suspend_complete+0x23/0x5b0 [i915]
> [ 62.034950] intel_runtime_suspend+0x16c/0x2a0 [i915]
> [ 62.034950] pci_pm_runtime_suspend+0x50/0x180
> [ 62.034951] ? pci_pm_runtime_resume+0xa0/0xa0
> [ 62.034952] __rpm_callback+0xc5/0x210
> [ 62.034953] rpm_callback+0x1f/0x80
> [ 62.034953] ? pci_pm_runtime_resume+0xa0/0xa0
> [ 62.034954] rpm_suspend+0x118/0x580
> [ 62.034955] pm_runtime_work+0x64/0x90
> [ 62.034956] process_one_work+0x1bb/0x3e0
> [ 62.034956] worker_thread+0x46/0x4f0
> [ 62.034957] ? __schedule+0x18b/0x610
> [ 62.034958] kthread+0xff/0x140
> [ 62.034958] ? process_one_work+0x3e0/0x3e0
> [ 62.034959] ? kthread_create_on_node+
>
> and related hard lockups in CI for byt and bsw.
>
> Note this effectively reverts commits 41ce405e6894 and b27366958869
> ("drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register()")
>
> Fixes: 41ce405e6894 ("drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register()")
> Fixes: b27366958869 ("drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register()")
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100718
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: Tomi Sarvela <tomi.p.sarvela at intel.com>
> ---
> drivers/gpu/drm/i915/i915_drv.c | 39 +++++++++++++++++----------------------
> 1 file changed, 17 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index e4f902f61e57..89b517c478e8 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -2179,6 +2179,17 @@ static void vlv_restore_gunit_s0ix_state(struct drm_i915_private *dev_priv)
> I915_WRITE(VLV_GUNIT_CLOCK_GATE2, s->clock_gate_dis2);
> }
>
> +static int vlv_wait_for_pw_status(struct drm_i915_private *dev_priv,
> + u32 mask, u32 val)
> +{
> + /* The HW does not like us polling for PW_STATUS frequently, so
> + * use the sleeping loop rather than risk the busy spin within
> + * intel_wait_for_register().
> + */
> + return wait_for((I915_READ_NOTRACE(VLV_GTLC_PW_STATUS) & mask) == val,
> + 3);
> +}
> +
> int vlv_force_gfx_clock(struct drm_i915_private *dev_priv, bool force_on)
> {
> u32 val;
> @@ -2208,7 +2219,7 @@ int vlv_force_gfx_clock(struct drm_i915_private *dev_priv, bool force_on)
> static int vlv_allow_gt_wake(struct drm_i915_private *dev_priv, bool allow)
> {
> u32 val;
> - int err = 0;
> + int err;
>
> val = I915_READ(VLV_GTLC_WAKE_CTRL);
> val &= ~VLV_GTLC_ALLOWWAKEREQ;
> @@ -2217,45 +2228,29 @@ static int vlv_allow_gt_wake(struct drm_i915_private *dev_priv, bool allow)
> I915_WRITE(VLV_GTLC_WAKE_CTRL, val);
> POSTING_READ(VLV_GTLC_WAKE_CTRL);
>
> - err = intel_wait_for_register(dev_priv,
> - VLV_GTLC_PW_STATUS,
> - VLV_GTLC_ALLOWWAKEACK,
> - allow,
> - 1);
> + err = vlv_wait_for_pw_status(dev_priv, VLV_GTLC_ALLOWWAKEACK, allow);
Looks a bit funny to wait for a boolean. Maybe 'allow ? VLV_GTLC_ALLOWWAKEACK : 0'
to make this a little less confusing?
> if (err)
> DRM_ERROR("timeout disabling GT waking\n");
>
> return err;
> }
>
> -static int vlv_wait_for_gt_wells(struct drm_i915_private *dev_priv,
> - bool wait_for_on)
> +static void vlv_wait_for_gt_wells(struct drm_i915_private *dev_priv,
> + bool wait_for_on)
> {
> u32 mask;
> u32 val;
> - int err;
>
> mask = VLV_GTLC_PW_MEDIA_STATUS_MASK | VLV_GTLC_PW_RENDER_STATUS_MASK;
> val = wait_for_on ? mask : 0;
> - if ((I915_READ(VLV_GTLC_PW_STATUS) & mask) == val)
> - return 0;
> -
> - DRM_DEBUG_KMS("waiting for GT wells to go %s (%08x)\n",
> - onoff(wait_for_on),
> - I915_READ(VLV_GTLC_PW_STATUS));
>
> /*
> * RC6 transitioning can be delayed up to 2 msec (see
> * valleyview_enable_rps), use 3 msec for safety.
> */
Maybe move the comment into vlv_wait_for_pw_status() as well since that's
where the timeout is specified now?
Haven't verfied the hardware issue myself, but the change looks sane enough, so
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> - err = intel_wait_for_register(dev_priv,
> - VLV_GTLC_PW_STATUS, mask, val,
> - 3);
> - if (err)
> + if (vlv_wait_for_pw_status(dev_priv, mask, val))
> DRM_ERROR("timeout waiting for GT wells to go %s\n",
> onoff(wait_for_on));
> -
> - return err;
> }
>
> static void vlv_check_no_gt_access(struct drm_i915_private *dev_priv)
> @@ -2276,7 +2271,7 @@ static int vlv_suspend_complete(struct drm_i915_private *dev_priv)
> * Bspec defines the following GT well on flags as debug only, so
> * don't treat them as hard failures.
> */
> - (void)vlv_wait_for_gt_wells(dev_priv, false);
> + vlv_wait_for_gt_wells(dev_priv, false);
>
> mask = VLV_GTLC_RENDER_CTX_EXISTS | VLV_GTLC_MEDIA_CTX_EXISTS;
> WARN_ON((I915_READ(VLV_GTLC_WAKE_CTRL) & mask) != mask);
> --
> 2.11.0
--
Ville Syrjälä
Intel OTC
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