[Intel-gfx] [RFC] Move BDW workarounds to ring init fn

[arun.siluvery at linux.intel.com]

From: Arun Siluvery <arun.siluvery at linux.intel.com>

This patch moves BDW workarounds from init_clock_gating() to render ring
init fn otherwise they are lost when gpu is reset.
In case of execlists, some of the workarounds modify registers that are
part of register state context which doesn't get initialized until
init_clock_gating(); this results in default context with incorrect values
as it is restored and saved before updated by workarounds.

Open issue:
For Wa4x4STCOptimizationDisable, we set CACHE_MODE_1[6:6] = 1
At the time when HW contexts are enabled after rings are initialized with
default context this workaround is valid but followed by a context switch
this is getting reset, please see below log snippet.

...
[    5.978209] [drm:i915_pages_create_for_stolen] offset=0x0, size=8294400
[    5.978213] [drm:intel_alloc_plane_obj] plane fb obj ffff8801472e0000
[    5.978215] [drm:i915_gem_setup_global_gtt] reserving preallocated space: 0 + 7e9000
[    5.978216] [drm:i915_gem_setup_global_gtt] clearing unused GTT space: [7e9000, fffff000]
[    5.979613] [drm:i915_gem_init] CACHE_MODE_1: 0x00000180
[    5.981372] [drm:gen8_ppgtt_init] Allocated 4 pages for page directories (0 wasted)
[    5.981373] [drm:gen8_ppgtt_init] Allocated 2048 pages for page tables (0 wasted)
[    5.981376] [drm:i915_gem_context_init] HW context support initialized
[    5.981462] [drm:i915_gem_init_hw] CACHE_MODE_1: 0x00000180
[    5.981467] [drm:i915_gem_init_rings] CACHE_MODE_1: 0x00000180
[    5.981704] [drm:bdw_init_workarounds] CACHE_MODE_1: 0x000001C0
[    5.981716] [drm:init_status_page] bsd ring hws offset: 0x0081e000
[    5.981792] [drm:init_status_page] blitter ring hws offset: 0x0083f000
[    5.981910] [drm:init_status_page] video enhancement ring hws offset: 0x00860000
[    5.982001] [drm:i915_gem_init_hw] CACHE_MODE_1: 0x000001C0
[    5.982104] [drm:i915_gem_context_enable] Switch render ring to default_context
[    5.982106] [drm:i915_gem_render_state_init] render ring: Render state init
[    5.982120] [drm:do_switch] render ring, CACHE_MODE_1: 0x000001C0, uninitialized: 1
[    5.982121] [drm:i915_gem_context_enable] Switch bsd ring to default_context
[    5.982122] [drm:do_switch] bsd ring, CACHE_MODE_1: 0x000001C0, uninitialized: 0
[    5.982123] [drm:i915_gem_context_enable] Switch blitter ring to default_context
[    5.982126] [drm:do_switch] blitter ring, CACHE_MODE_1: 0x000001C0, uninitialized: 0
[    5.982126] [drm:i915_gem_context_enable] Switch video enhancement ring to default_context
[    5.982128] [drm:do_switch] video enhancement ring, CACHE_MODE_1: 0x000001C0, uninitialized: 0
[    5.982133] [drm:i915_gem_init] CACHE_MODE_1: 0x000001C0
[    5.982258] [drm:intel_init_clock_gating]
...
[   10.037019] [drm:do_switch] blitter ring, CACHE_MODE_1: 0x00000180, uninitialized: 0
...
[   10.488145] [drm:do_switch] render ring, CACHE_MODE_1: 0x00000180, uninitialized: 0
...

I am currently testing this with an igt which triggers a gpu reset and compares
WA register contents before and after reset but the test fails because of
this register hence not sending it now.
Please let me know how to keep this WA valid after a context switch.


Arun Siluvery (1):
  drm/i915/bdw: Initialize BDW workarounds in render ring init fn

 drivers/gpu/drm/i915/i915_debugfs.c     | 46 ++++++++++++++++++++++
 drivers/gpu/drm/i915/intel_pm.c         | 59 ----------------------------
 drivers/gpu/drm/i915/intel_ringbuffer.c | 68 +++++++++++++++++++++++++++++++++
 3 files changed, 114 insertions(+), 59 deletions(-)

-- 
1.9.2