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f8973c217f
linux/drivers/gpu/drm/i915
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Chris Wilson f8973c217f drm/i915: Add a delay between interrupt and inspecting the final seqno (ilk) 
On Ironlake, there is no command nor register to ensure that the write
from a MI_STORE command is completed (and coherent on the CPU) before the
command parser continues. This means that the ordering between the seqno
write and the subsequent user interrupt is undefined (like gen6+). So to
ensure that the seqno write is completed after the final user interrupt
we need to delay the read sufficiently to allow the write to complete.
This delay is undefined by the bspec, and empirically requires 75us even
though a register read combined with a clflush is less than 500ns. Hence,
the delay is due to an on-chip buffer rather than the latency of the write
to memory.

Note that the render ring controls this by filling the PIPE_CONTROL fifo
with stalling commands that force the earliest pipe-control with the
seqno to be completed before the command parser continues. Given that we
need a barrier operation for BSD, we may as well forgo the extra
per-batch latency by using a common per-interrupt barrier.

Studying the impact of adding the usleep shows that in both sequences of
and individual synchronous no-op batches is negligible for the media
engine (where the write now is unordered with the interrupt). Converting
the render engine over from the current glutton of pie-controls over to
the per-interrupt delays speeds up both the sequential and individual
synchronous no-ops by 20% and 60%, respectively. This speed up holds
even when looking at the throughput of small copies (4KiB->4MiB), both
serial and synchronous, by about 20%. This is because despite adding a
significant delay to the interrupt, in all likelihood we will see the
seqno write without having to apply the barrier (only in the rare corner
cases where the write is delayed on the last required is the delay
necessary).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94307
Testcase: igt/gem_sync #ilk
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1467390209-3576-12-git-send-email-chris@chris-wilson.co.uk
2016-07-01 21:00:53 +01:00
..
gvt drm/i915: gvt: Introduce the basic architecture of GVT-g 2016-06-17 20:35:06 +01:00
dvo_ch7xxx.c
dvo_ch7017.c
dvo_ivch.c
dvo_ns2501.c
dvo_sil164.c
dvo_tfp410.c
dvo.h
i915_cmd_parser.c drm/i915: Fix a buch of kerneldoc warnings 2016-06-06 13:04:26 +01:00
i915_debugfs.c drm/i915: Use HWS for seqno tracking everywhere 2016-07-01 20:58:48 +01:00
i915_drv.c drm/i915: Remove the dedicated hangcheck workqueue 2016-07-01 20:42:29 +01:00
i915_drv.h drm/i915: Use HWS for seqno tracking everywhere 2016-07-01 20:58:48 +01:00
i915_gem_batch_pool.c drm/i915: Propagate error from drm_gem_object_init() 2016-04-28 12:28:58 +03:00
i915_gem_batch_pool.h
i915_gem_context.c drm/i915: Mark all default contexts as uninitialised after context loss 2016-06-24 15:02:55 +01:00
i915_gem_debug.c drm/i915: replace for_each_engine() 2016-03-24 14:34:11 +00:00
i915_gem_dmabuf.c Linux 4.6-rc3 2016-04-11 19:25:13 +02:00
i915_gem_dmabuf.h drm/i915: Serialise presentation with imported dmabufs 2016-06-17 10:32:26 +01:00
i915_gem_evict.c drm/i915: Only switch to default context when evicting from GGTT 2016-06-24 15:03:32 +01:00
i915_gem_execbuffer.c drm: Extract drm_is_current_master 2016-06-21 21:58:12 +02:00
i915_gem_fence.c drm/i915: Introduce & use new lightweight SGL iterators 2016-05-20 13:43:00 +01:00
i915_gem_gtt.c drm/i915: tweak gen6_for_{each_pde, all_pdes} macros 2016-06-27 13:13:53 +01:00
i915_gem_gtt.h drm/i915: tweak gen6_for_{each_pde, all_pdes} macros 2016-06-27 13:13:53 +01:00
i915_gem_render_state.c drm/i915:bxt: Enable Pooled EU support 2016-06-14 10:42:35 +01:00
i915_gem_render_state.h
i915_gem_shrinker.c drm/i915/shrinker: Flush active on objects before counting 2016-07-01 20:42:27 +01:00
i915_gem_stolen.c drm/i915/kbl: Add WaSkipStolenMemoryFirstPage for A0 2016-06-08 16:20:23 +03:00
i915_gem_tiling.c Merge branch 'drm-intel-next' of git://anongit.freedesktop.org/drm-intel into drm-next 2016-06-02 07:58:36 +10:00
i915_gem_userptr.c drm/i915: Introduce & use new lightweight SGL iterators 2016-05-20 13:43:00 +01:00
i915_gem.c drm/i915: Spin after waking up for an interrupt 2016-07-01 20:58:47 +01:00
i915_gem.h drm/i915: Add GEM debugging Kconfig option 2016-04-14 10:45:40 +01:00
i915_gpu_error.c drm/i915: Use HWS for seqno tracking everywhere 2016-07-01 20:58:48 +01:00
i915_guc_reg.h drm/i915/bxt: reserve space for RC6 in the the GuC WOPCM 2016-05-18 12:49:19 +01:00
i915_guc_submission.c drm/i915/guc: Remove one unnecessary variable 2016-06-21 15:43:32 +01:00
i915_ioc32.c
i915_irq.c drm/i915: Add a delay between interrupt and inspecting the final seqno (ilk) 2016-07-01 21:00:53 +01:00
i915_params.c drm/i915: Set the access right of kernel param "i915.enable_gvt" to read-only. 2016-06-21 11:45:27 +01:00
i915_params.h drm/i915: gvt: Introduce the basic architecture of GVT-g 2016-06-17 20:35:06 +01:00
i915_pci.c drm/i915/bxt: Remove the preliminary_hw_support flag 2016-07-01 21:25:54 +03:00
i915_pvinfo.h drm/i915: Use offsetof() to calculate the offset of members in PVINFO page 2016-06-17 19:44:25 +01:00
i915_reg.h drm/i915/bxt: Fix sanity check for BIOS RC6 setup 2016-07-01 14:57:20 +03:00
i915_suspend.c
i915_sysfs.c drm/i915: No need to wait for idle on L3 remap 2016-06-24 15:03:06 +01:00
i915_trace_points.c
i915_trace.h drm/i915: Use HWS for seqno tracking everywhere 2016-07-01 20:58:48 +01:00
i915_vgpu.c drm/i915: Fold vGPU active check into inner functions 2016-06-17 19:44:29 +01:00
i915_vgpu.h drm/i915: Fold vGPU active check into inner functions 2016-06-17 19:44:29 +01:00
intel_acpi.c
intel_atomic_plane.c drm/i915: Revert async unpin and nonblocking atomic commit 2016-06-01 09:46:46 +02:00
intel_atomic.c drm: Consolidate plane arrays in drm_atomic_state 2016-06-02 17:20:25 +02:00
intel_audio.c Merge branch 'drm-next' of git://people.freedesktop.org/~airlied/linux 2016-05-23 11:48:48 -07:00
intel_bios.c drm/i915: Check VBT for port presence in addition to the strap on VLV/CHV 2016-06-07 18:45:43 +03:00
intel_bios.h drm/i915: Parse LFP brightness control field in VBT 2016-05-02 16:17:38 +03:00
intel_breadcrumbs.c drm/i915: Use HWS for seqno tracking everywhere 2016-07-01 20:58:48 +01:00
intel_color.c drm: drm_helper_crtc_enable_color_mgmt() => drm_crtc_enable_color_mgmt() 2016-06-07 17:10:49 +03:00
intel_crt.c drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register() 2016-06-30 15:42:02 +01:00
intel_csr.c drm/i915/dmc: Step away from symbolic links 2016-06-27 14:26:16 -07:00
intel_ddi.c drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register() 2016-06-30 15:42:03 +01:00
intel_display.c drm/i915: Spin after waking up for an interrupt 2016-07-01 20:58:47 +01:00
intel_dp_aux_backlight.c drm/i915: Add Backlight Control using DPCD for eDP connectors (v9) 2016-04-26 15:17:54 +03:00
intel_dp_link_training.c drm/i915: Revert DisplayPort fast link training feature 2016-06-20 12:37:07 +03:00
intel_dp_mst.c drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register() 2016-06-30 15:42:15 +01:00
intel_dp.c drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register() 2016-06-30 15:42:14 +01:00
intel_dpio_phy.c drm/i915: Move VLV HDMI lane reset work around logic to intel_dpio_phy.c 2016-04-29 09:59:00 +03:00
intel_dpll_mgr.c drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register() 2016-06-30 15:42:16 +01:00
intel_dpll_mgr.h
intel_drv.h drm/i915: Use atomic waits for short non-atomic ones 2016-06-29 15:53:15 +01:00
intel_dsi_dcs_backlight.c drm/i915/dsi: CABC support for Panel PWM backlight control 2016-05-17 16:12:39 +03:00
intel_dsi_panel_vbt.c drm/i915/dsi: add support for gpio elements on CHV 2016-04-27 09:48:17 +03:00
intel_dsi_pll.c drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register() 2016-06-30 15:42:20 +01:00
intel_dsi.c drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register() 2016-06-30 15:42:19 +01:00
intel_dsi.h drm/i915/dsi: CABC support for Panel PWM backlight control 2016-05-17 16:12:39 +03:00
intel_dvo.c drm/i915: Move connector registration to driver registration 2016-06-24 14:43:26 +01:00
intel_fbc.c drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register() 2016-06-30 15:42:21 +01:00
intel_fbdev.c drm/i915/fbdev: Flush mode configuration before lastclose 2016-06-21 09:36:56 +01:00
intel_fifo_underrun.c drm/i915: Do not use {HAS_*, IS_*, INTEL_INFO}(dev_priv->dev) 2016-04-07 14:50:26 +03:00
intel_frontbuffer.c
intel_guc_fwif.h drm/i915/guc: rework guc_add_workqueue_item() 2016-05-23 14:21:53 +01:00
intel_guc_loader.c drm/i915/guc: don't ever forward VBlank to the GuC 2016-06-27 13:21:59 +01:00
intel_guc.h drm/i915/guc: index host arrays by i915 engine ID, not guc_id 2016-06-21 11:24:25 +01:00
intel_gvt.c drm/i915/gvt: Mark i915.enable_gvt as false if loading fails 2016-06-21 12:40:13 +01:00
intel_gvt.h drm/i915: gvt: Introduce the basic architecture of GVT-g 2016-06-17 20:35:06 +01:00
intel_hdmi.c drm/i915: Move connector registration to driver registration 2016-06-24 14:43:26 +01:00
intel_hotplug.c drm/i915: Small display interrupt handlers tidy 2016-05-09 13:38:16 +01:00
intel_i2c.c drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register() 2016-06-30 15:42:22 +01:00
intel_lrc.c drm/i915: Refactor scratch object allocation for gen2 w/a buffer 2016-07-01 21:00:50 +01:00
intel_lrc.h drm/i915: Introduce execlist context status change notification 2016-06-17 20:36:19 +01:00
intel_lvds.c drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register() 2016-06-30 15:42:23 +01:00
intel_mocs.c drm/i915/mocs: || vs | typo in get_mocs_settings() 2016-06-13 17:38:01 +03:00
intel_mocs.h drm/i915/mocs: Program MOCS for all engines on init 2016-04-14 10:45:40 +01:00
intel_modes.c
intel_opregion.c drm/i915/opregion: handle missing connector types for acpi display types 2016-06-29 17:41:50 +03:00
intel_overlay.c Merge branch 'drm-intel-next' of git://anongit.freedesktop.org/drm-intel into drm-next 2016-06-02 07:58:36 +10:00
intel_panel.c drm/i915: Move backlight registration to connector registration 2016-06-24 14:43:14 +01:00
intel_pm.c drm/i915: Spin after waking up for an interrupt 2016-07-01 20:58:47 +01:00
intel_psr.c drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register() 2016-06-30 15:42:25 +01:00
intel_renderstate_gen6.c
intel_renderstate_gen7.c
intel_renderstate_gen8.c
intel_renderstate_gen9.c
intel_renderstate.h
intel_ringbuffer.c drm/i915: Add a delay between interrupt and inspecting the final seqno (ilk) 2016-07-01 21:00:53 +01:00
intel_ringbuffer.h drm/i915: Refactor scratch object allocation for gen2 w/a buffer 2016-07-01 21:00:50 +01:00
intel_runtime_pm.c drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register() 2016-06-30 17:05:41 +01:00
intel_sdvo_regs.h
intel_sdvo.c drm/i915: Move connector registration to driver registration 2016-06-24 14:43:26 +01:00
intel_sideband.c drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register() 2016-06-30 15:42:33 +01:00
intel_sprite.c drm/i915: Signal drm events for atomic 2016-06-16 14:28:34 +02:00
intel_tv.c drm/i915: Move connector registration to driver registration 2016-06-24 14:43:26 +01:00
intel_uncore.c drm/i915: Convert wait_for(I915_READ(reg)) to intel_wait_for_register() 2016-06-30 17:05:07 +01:00
intel_vbt_defs.h drm/i915: Extract physical display dimensions from VBT 2016-06-02 14:33:09 +03:00
Kconfig drm/i915: gvt: Introduce the basic architecture of GVT-g 2016-06-17 20:35:06 +01:00
Kconfig.debug drm/i915/debug: Select PREEMPT_COUNT when enabling debugging 2016-06-29 15:53:14 +01:00
Makefile drm/i915: Slaughter the thundering i915_wait_request herd 2016-07-01 20:58:43 +01:00