target/linux/bcm27xx/patches-4.19/950-0496-drm-v3d-Drop-the-wait-for-L2T-flush-to-complete.patch

   1 From 9d8fa62500ae52348d36766e70b49c7508addaf3 Mon Sep 17 00:00:00 2001
   2 From: Eric Anholt <eric@anholt.net>
   3 Date: Mon, 3 Dec 2018 14:24:36 -0800
   4 Subject: [PATCH] drm/v3d: Drop the wait for L2T flush to complete.
   5
   6 According to Dave, once you've started an L2T flush, all L2T accesses
   7 will be blocked until the flush completes.  This fixes a consistent
   8 3-4ms stall between the ioctl and running the job, and 3DMMES Taiji
   9 goes from 27fps to 110fps.
  10
  11 v2: Leave a note about why we don't need to wait for completion.
  12
  13 Signed-off-by: Eric Anholt <eric@anholt.net>
  14 Fixes: 57692c94dcbe ("drm/v3d: Introduce a new DRM driver for Broadcom V3D V3.x+")
  15 Reviewed-by: Dave Emett <david.emett@broadcom.com>
  16 Link: https://patchwork.freedesktop.org/patch/msgid/20181203222438.25417-4-eric@anholt.net
  17 (cherry picked from commit 51c1b6f9eb3dbdec91b0e3c89f623e634c996bbb)
  18 ---
  19  drivers/gpu/drm/v3d/v3d_gem.c | 8 ++++----
  20  1 file changed, 4 insertions(+), 4 deletions(-)
  21
  22 --- a/drivers/gpu/drm/v3d/v3d_gem.c
  23 +++ b/drivers/gpu/drm/v3d/v3d_gem.c
  24 @@ -143,13 +143,13 @@ v3d_invalidate_l2(struct v3d_dev *v3d, i
  25  static void
  26  v3d_flush_l2t(struct v3d_dev *v3d, int core)
  27  {
  28 +       /* While there is a busy bit (V3D_L2TCACTL_L2TFLS), we don't
  29 +        * need to wait for completion before dispatching the job --
  30 +        * L2T accesses will be stalled until the flush has completed.
  31 +        */
  32         V3D_CORE_WRITE(core, V3D_CTL_L2TCACTL,
  33                        V3D_L2TCACTL_L2TFLS |
  34                        V3D_SET_FIELD(V3D_L2TCACTL_FLM_FLUSH, V3D_L2TCACTL_FLM));
  35 -       if (wait_for(!(V3D_CORE_READ(core, V3D_CTL_L2TCACTL) &
  36 -                      V3D_L2TCACTL_L2TFLS), 100)) {
  37 -               DRM_ERROR("Timeout waiting for L2T flush\n");
  38 -       }
  39  }
  40
  41  /* Invalidates the slice caches.  These are read-only caches. */