[Mesa-dev] [PATCH 01/18] i965: Query whether we have kernel support for the TIMESTAMP register once

[Chris Wilson]

Move the query for the TIMESTAMP register from context init to the
screen, so that it is only queried once for all contexts.

On 32bit systems, some old kernels trigger a hw bug resulting in the
TIMESTAMP register being shifted and the low bits always zero. Detect
this by repeating the read a few times and check the register is
incrementing.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 src/mesa/drivers/dri/i965/intel_extensions.c |  6 +-----
 src/mesa/drivers/dri/i965/intel_screen.c     | 15 +++++++++++++++
 src/mesa/drivers/dri/i965/intel_screen.h     |  2 ++
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/intel_extensions.c b/src/mesa/drivers/dri/i965/intel_extensions.c
index 3423190..740ac81 100644
--- a/src/mesa/drivers/dri/i965/intel_extensions.c
+++ b/src/mesa/drivers/dri/i965/intel_extensions.c
@@ -282,8 +282,6 @@ intelInitExtensions(struct gl_context *ctx)
    }
 
    if (brw->gen >= 6) {
-      uint64_t dummy;
-
       ctx->Extensions.ARB_blend_func_extended =
          !driQueryOptionb(&brw->optionCache, "disable_blend_func_extended");
       ctx->Extensions.ARB_conditional_render_inverted = true;
@@ -307,9 +305,7 @@ intelInitExtensions(struct gl_context *ctx)
       ctx->Extensions.EXT_transform_feedback = true;
       ctx->Extensions.OES_depth_texture_cube_map = true;
 
-      /* Test if the kernel has the ioctl. */
-      if (drm_intel_reg_read(brw->bufmgr, TIMESTAMP, &dummy) == 0)
-         ctx->Extensions.ARB_timer_query = true;
+      ctx->Extensions.ARB_timer_query = brw->intelScreen->hw_has_timestamp;
 
       /* Only enable this in core profile because other parts of Mesa behave
        * slightly differently when the extension is enabled.
diff --git a/src/mesa/drivers/dri/i965/intel_screen.c b/src/mesa/drivers/dri/i965/intel_screen.c
index f9398d7..839a984 100644
--- a/src/mesa/drivers/dri/i965/intel_screen.c
+++ b/src/mesa/drivers/dri/i965/intel_screen.c
@@ -1123,6 +1123,20 @@ intel_detect_swizzling(struct intel_screen *screen)
       return true;
 }
 
+static bool
+intel_detect_timestamp(struct intel_screen *screen)
+{
+   uint64_t dummy = 0;
+   int loop = 10;
+
+   do {
+      if (drm_intel_reg_read(screen->bufmgr, TIMESTAMP, &dummy))
+	 return false;
+   } while ((dummy & 0xffffffff) == 0 && --loop);
+
+   return loop > 0;
+}
+
 /**
  * Return array of MSAA modes supported by the hardware. The array is
  * zero-terminated and sorted in decreasing order.
@@ -1378,6 +1392,7 @@ __DRIconfig **intelInitScreen2(__DRIscreen *psp)
    intelScreen->hw_must_use_separate_stencil = intelScreen->devinfo->gen >= 7;
 
    intelScreen->hw_has_swizzling = intel_detect_swizzling(intelScreen);
+   intelScreen->hw_has_timestamp = intel_detect_timestamp(intelScreen);
 
    const char *force_msaa = getenv("INTEL_FORCE_MSAA");
    if (force_msaa) {
diff --git a/src/mesa/drivers/dri/i965/intel_screen.h b/src/mesa/drivers/dri/i965/intel_screen.h
index 742b3d3..941e0fc 100644
--- a/src/mesa/drivers/dri/i965/intel_screen.h
+++ b/src/mesa/drivers/dri/i965/intel_screen.h
@@ -52,6 +52,8 @@ struct intel_screen
 
    bool hw_has_swizzling;
 
+   bool hw_has_timestamp;
+
    /**
     * Does the kernel support context reset notifications?
     */
-- 
2.1.4