Re: [PATCH 1/2] drm/i915/bdw: Apply workarounds in render ring init function

[Chris Wilson <chris@chris-wilson.co.uk>]

On Tue, Aug 26, 2014 at 11:16:29AM +0100, Siluvery, Arun wrote:
> On 26/08/2014 11:09, Chris Wilson wrote:
> >On Tue, Aug 26, 2014 at 10:33:16AM +0100, Arun Siluvery wrote:
> >>For BDW workarounds are currently initialized in init_clock_gating() but
> >>they are lost during reset, suspend/resume etc; this patch moves the WAs
> >>that are part of register state context to render ring init fn otherwise
> >>default context ends up with incorrect values as they don't get initialized
> >>until init_clock_gating fn.
> >>
> >>v2: Add workarounds to golden render state
> >>This method has its own issues, first of all this is different for
> >>each gen and it is generated using a tool so adding new workaround
> >>and mainitaining them across gens is not a straightforward process.
> >>
> >>v3: Use LRIs to emit these workarounds (Ville)
> >>Instead of modifying the golden render state the same LRIs are
> >>emitted from within the driver.
> >>
> >>For: VIZ-4092
> >>Signed-off-by: Arun Siluvery <arun.siluvery@linux.intel.com>
> >>---
> >>  drivers/gpu/drm/i915/i915_gem_context.c |  6 +++
> >>  drivers/gpu/drm/i915/intel_pm.c         | 48 --------------------
> >>  drivers/gpu/drm/i915/intel_ringbuffer.c | 78 +++++++++++++++++++++++++++++++++
> >>  drivers/gpu/drm/i915/intel_ringbuffer.h |  1 +
> >>  4 files changed, 85 insertions(+), 48 deletions(-)
> >>
> >>diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
> >>index 9683e62..2debce4 100644
> >>--- a/drivers/gpu/drm/i915/i915_gem_context.c
> >>+++ b/drivers/gpu/drm/i915/i915_gem_context.c
> >>@@ -631,20 +631,26 @@ static int do_switch(struct intel_engine_cs *ring,
> >>  	}
> >>
> >>  	uninitialized = !to->legacy_hw_ctx.initialized && from == NULL;
> >>  	to->legacy_hw_ctx.initialized = true;
> >>
> >>  done:
> >>  	i915_gem_context_reference(to);
> >>  	ring->last_context = to;
> >>
> >>  	if (uninitialized) {
> >>+		if (IS_BROADWELL(ring->dev)) {
> >>+			ret = bdw_init_workarounds(ring);
> >>+			if (ret)
> >>+				DRM_ERROR("init workarounds: %d\n", ret);
> >
> >A good rule of thumb is that if you are exporting gen specific routines,
> >the layering and abstraction is fishy.
> >-Chris
> >
> ok, so something like i915_init_workarounds() is ok? with a check
> for bdw/gen8 done inside that function.

Except for init_workarounds is quite useless as a function name and we
already have a structure that is already customised per-engine and
per-gen that you could hook into.
engine->ring_init_context() ?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre