[Mesa-dev] [PATCH 2/5] i965: Share the workaround bo between all contexts

[Chris Wilson]

Since the workaround bo is used strictly as a write-only buffer, we need
only allocate one per screen and use the same one from all contexts.

(The caveat here is during extension initialisation, where we write into
and read back register values from the buffer, but that is performed only
once for the first context - and baring synchronisation issues should not
be a problem. Safer would be to move that also to the screen.)

v2: Give the workaround bo its own init function and don't piggy back
intel_bufmgr_init() since it is not that related.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Kenneth Graunke <kenneth at whitecape.org>
Cc: Martin Peres <martin.peres at linux.intel.com>
---
 src/mesa/drivers/dri/i965/brw_context.c      |  7 +------
 src/mesa/drivers/dri/i965/brw_context.h      |  4 ++--
 src/mesa/drivers/dri/i965/brw_pipe_control.c | 13 ++++---------
 src/mesa/drivers/dri/i965/intel_screen.c     | 15 +++++++++++++++
 src/mesa/drivers/dri/i965/intel_screen.h     |  1 +
 5 files changed, 23 insertions(+), 17 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
index 8150b94..3dac01b 100644
--- a/src/mesa/drivers/dri/i965/brw_context.c
+++ b/src/mesa/drivers/dri/i965/brw_context.c
@@ -819,12 +819,7 @@ brwCreateContext(gl_api api,
       }
    }
 
-   if (brw_init_pipe_control(brw, devinfo)) {
-      *dri_ctx_error = __DRI_CTX_ERROR_NO_MEMORY;
-      intelDestroyContext(driContextPriv);
-      return false;
-   }
-
+   brw_init_pipe_control(brw, devinfo);
    brw_init_state(brw);
 
    intelInitExtensions(ctx);
diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
index 7f73b10..3397336 100644
--- a/src/mesa/drivers/dri/i965/brw_context.h
+++ b/src/mesa/drivers/dri/i965/brw_context.h
@@ -2002,8 +2002,8 @@ gen9_use_linear_1d_layout(const struct brw_context *brw,
                           const struct intel_mipmap_tree *mt);
 
 /* brw_pipe_control.c */
-int brw_init_pipe_control(struct brw_context *brw,
-			  const struct brw_device_info *info);
+void brw_init_pipe_control(struct brw_context *brw,
+                           const struct brw_device_info *info);
 void brw_fini_pipe_control(struct brw_context *brw);
 
 void brw_emit_pipe_control_flush(struct brw_context *brw, uint32_t flags);
diff --git a/src/mesa/drivers/dri/i965/brw_pipe_control.c b/src/mesa/drivers/dri/i965/brw_pipe_control.c
index 7ee3cb6..872bfe8 100644
--- a/src/mesa/drivers/dri/i965/brw_pipe_control.c
+++ b/src/mesa/drivers/dri/i965/brw_pipe_control.c
@@ -330,26 +330,21 @@ brw_emit_mi_flush(struct brw_context *brw)
    brw_render_cache_set_clear(brw);
 }
 
-int
+void
 brw_init_pipe_control(struct brw_context *brw,
                       const struct brw_device_info *devinfo)
 {
    if (devinfo->gen < 6)
-      return 0;
+      return;
 
    /* We can't just use brw_state_batch to get a chunk of space for
     * the gen6 workaround because it involves actually writing to
     * the buffer, and the kernel doesn't let us write to the batch.
     */
-   brw->workaround_bo = drm_intel_bo_alloc(brw->bufmgr,
-                                           "pipe_control workaround",
-                                           4096, 4096);
-   if (brw->workaround_bo == NULL)
-      return -ENOMEM;
+   brw->workaround_bo = brw->intelScreen->workaround_bo;
+   drm_intel_bo_reference(brw->workaround_bo);
 
    brw->pipe_controls_since_last_cs_stall = 0;
-
-   return 0;
 }
 
 void
diff --git a/src/mesa/drivers/dri/i965/intel_screen.c b/src/mesa/drivers/dri/i965/intel_screen.c
index c0f5c92..71f2957 100644
--- a/src/mesa/drivers/dri/i965/intel_screen.c
+++ b/src/mesa/drivers/dri/i965/intel_screen.c
@@ -961,6 +961,7 @@ intelDestroyScreen(__DRIscreen * sPriv)
 {
    struct intel_screen *intelScreen = sPriv->driverPrivate;
 
+   drm_intel_bo_unreference(intelScreen->workaround_bo);
    dri_bufmgr_destroy(intelScreen->bufmgr);
    driDestroyOptionInfo(&intelScreen->optionCache);
 
@@ -1100,6 +1101,17 @@ intel_init_bufmgr(struct intel_screen *intelScreen)
 }
 
 static bool
+intel_init_workaround_bo(struct intel_screen *intelScreen)
+{
+   /* A small scratch bo shared by all contexts, primarily used
+    * for doing PIPECONTROL serialisation writes that are discarded.
+    */
+   intelScreen->workaround_bo =
+      drm_intel_bo_alloc(intelScreen->bufmgr, "pipe_control w/a", 4096, 4096);
+   return intelScreen->workaround_bo != NULL;
+}
+
+static bool
 intel_detect_swizzling(struct intel_screen *screen)
 {
    drm_intel_bo *buffer;
@@ -1388,6 +1400,9 @@ __DRIconfig **intelInitScreen2(__DRIscreen *psp)
    if (!intel_init_bufmgr(intelScreen))
        return false;
 
+   if (!intel_init_workaround_bo(intelScreen))
+       return false;
+
    intelScreen->deviceID = drm_intel_bufmgr_gem_get_devid(intelScreen->bufmgr);
    intelScreen->devinfo = brw_get_device_info(intelScreen->deviceID,
                                               brw_get_revision(psp->fd));
diff --git a/src/mesa/drivers/dri/i965/intel_screen.h b/src/mesa/drivers/dri/i965/intel_screen.h
index 941e0fc..e55fddb 100644
--- a/src/mesa/drivers/dri/i965/intel_screen.h
+++ b/src/mesa/drivers/dri/i965/intel_screen.h
@@ -60,6 +60,7 @@ struct intel_screen
    bool has_context_reset_notification;
 
    dri_bufmgr *bufmgr;
+   drm_intel_bo *workaround_bo;
 
    /**
     * A unique ID for shader programs.
-- 
2.1.4