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author | Chris Wilson | 2017-11-24 14:00:30 +0100 |
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committer | Chris Wilson | 2017-11-24 17:09:51 +0100 |
commit | a54b1873c0e3ffec3041cf72cb10d986d6bc4fe5 (patch) | |
tree | 2d9f9d176c3d3b6eb2da1253678d66f545ad1f85 /drivers/gpu/drm/i915/intel_pm.c | |
parent | drm/i915/guc: Tidy ELSP port assignment (diff) | |
download | kernel-qcow2-linux-a54b1873c0e3ffec3041cf72cb10d986d6bc4fe5.tar.gz kernel-qcow2-linux-a54b1873c0e3ffec3041cf72cb10d986d6bc4fe5.tar.xz kernel-qcow2-linux-a54b1873c0e3ffec3041cf72cb10d986d6bc4fe5.zip |
drm/i915: Use exponential backoff for wait_for()
Instead of sleeping for a fixed 1ms (roughly, depending on timer slack),
start with a small sleep and exponentially increase the sleep on each
cycle.
A good example of a beneficiary is the guc mmio communication channel.
Typically we expect (and so spin) for 10us for a quick response, but this
doesn't cover everything and so sometimes we fallback to the millisecond+
sleep. This incurs a significant delay in time-critical operations like
preemption (igt/gem_exec_latency), which can be improved significantly by
using a small sleep after the spin fails.
We've made this suggestion many times, but had little experimental data
to support adding the complexity.
v2: Bump the minimum usleep to 10us on advice of
Documentation/timers/timers-howto.txt (Tvrko)
v3: Specify min, max range for usleep intervals -- some code may
crucially depend upon and so want to specify the sleep pattern.
References: 1758b90e38f5 ("drm/i915: Use a hybrid scheme for fast register waits")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: John Harrison <John.C.Harrison@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171124130031.20761-2-chris@chris-wilson.co.uk
Diffstat (limited to 'drivers/gpu/drm/i915/intel_pm.c')
-rw-r--r-- | drivers/gpu/drm/i915/intel_pm.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c index 03d67d8ab647..a80c322c5b43 100644 --- a/drivers/gpu/drm/i915/intel_pm.c +++ b/drivers/gpu/drm/i915/intel_pm.c @@ -9294,7 +9294,7 @@ int skl_pcode_request(struct drm_i915_private *dev_priv, u32 mbox, u32 request, ret = 0; goto out; } - ret = _wait_for(COND, timeout_base_ms * 1000, 10); + ret = _wait_for(COND, timeout_base_ms * 1000, 10, 10); if (!ret) goto out; |