[Intel-gfx] [PATCH] drm/i915/guc: Don't make assumptions while getting the lrca offset

[Chris Wilson]

Quoting Chris Wilson (2017-07-12 01:00:02)
> Also feel free to try and fixup the other confusion in intel_lrc.c.
> Perhaps something like:
> 
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index b0738d2..f498aa6 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -2031,8 +2031,9 @@ static int execlists_context_deferred_alloc(struct i915_gem_context *ctx,
>  
>         context_size = round_up(engine->context_size, I915_GTT_PAGE_SIZE);
>  
> -       /* One extra page as the sharing data between driver and GuC */
> -       context_size += PAGE_SIZE * LRC_PPHWSP_PN;
> +       /* Add an extra page at the start for sharing data with the GuC */
> +       BUILD_BUG_ON(LRC_PPHWSP_PN != 1);
> +       context_size += PAGE_SIZE;
>  
>         ctx_obj = i915_gem_object_create(ctx->i915, context_size);
>         if (IS_ERR(ctx_obj)) {

Or better

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index b0738d2..0b7fb38 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -2031,8 +2031,8 @@ static int execlists_context_deferred_alloc(struct i915_gem_context *ctx,
 
        context_size = round_up(engine->context_size, I915_GTT_PAGE_SIZE);
 
-       /* One extra page as the sharing data between driver and GuC */
-       context_size += PAGE_SIZE * LRC_PPHWSP_PN;
+       /* Add an extra page at the start for sharing data with the GuC */
+       context_size += LRC_GUCSHR_PAGES * PAGE_SIZE;
 
        ctx_obj = i915_gem_object_create(ctx->i915, context_size);
        if (IS_ERR(ctx_obj)) {
diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index 52b3a1f..848ca21 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -72,7 +72,8 @@ int logical_xcs_ring_init(struct intel_engine_cs *engine);
 
 /* One extra page is added before LRC for GuC as shared data */
 #define LRC_GUCSHR_PN  (0)
-#define LRC_PPHWSP_PN  (LRC_GUCSHR_PN + 1)
+#define LRC_GUCSHR_PAGES 1
+#define LRC_PPHWSP_PN  (LRC_GUCSHR_PN + LRC_GUCSHR_PAGES)
 #define LRC_STATE_PN   (LRC_PPHWSP_PN + 1)
 
 struct drm_i915_private;

Nowhere do we use LRC_GUCSHR_PN. Having it just gives us the mirage of
flexibility...
-Chris