[Intel-gfx] [PATCH 2/2] drm/i915: write fence reg only once on VGPU

[Zhao, Yakui]

>-----Original Message-----
>From: Zhao, Yakui
>Sent: Tuesday, July 3, 2018 10:22 AM
>To: intel-gfx at lists.freedesktop.org
>Cc: zhenyuw at linux.intel.com; Zhao, Yakui <yakui.zhao at intel.com>
>Subject: [PATCH 2/2] drm/i915: write fence reg only once on VGPU
>
>On VGPU scenario the read/write operation of fence_reg will be trapped by
>the GVT-g. And then gvt-g follows the HW spec to write the fence_reg.
>So it is unnecessary to read/write fence reg several times. This will help to
>reduce the unnecessary trap of fence_reg mmio operation.
>

Sorry for one typo. The V2 will be sent.

>Signed-off-by: Zhao Yakui <yakui.zhao at intel.com>
>---
> drivers/gpu/drm/i915/i915_gem_fence_reg.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
>diff --git a/drivers/gpu/drm/i915/i915_gem_fence_reg.c
>b/drivers/gpu/drm/i915/i915_gem_fence_reg.c
>index d92fe03..55bf6d9 100644
>--- a/drivers/gpu/drm/i915/i915_gem_fence_reg.c
>+++ b/drivers/gpu/drm/i915/i915_gem_fence_reg.c
>@@ -95,11 +95,15 @@ static void i965_write_fence_reg(struct
>drm_i915_fence_reg *fence,
>
> 	if (INTEL_GEN(fence->i915) >= 6) {
> 		/* Use the 64-bit RW to read/write fence reg on SNB+ */
>-		I915_WRITE64_FW(fence_reg_lo, 0);
>-		I915_READ64(fence_reg_lo);
>-
>-		I915_WRITE64_FW(fence_reg_lo, val);
>-		I915_READ64(fence_reg_lo);
>+		if (intel_vgpu_active(i915))
>+			I915_WRITE64_FW(fence_reg_lo, val);
>+		else {
>+			I915_WRITE64_FW(fence_reg_lo, 0);
>+			I915_READ64(fence_reg_lo);
>+
>+			I915_WRITE64_FW(fence_reg_lo, val);
>+			I915_READ64(fence_reg_lo);
>+		}
> 	} else {
> 		/* To w/a incoherency with non-atomic 64-bit register updates,
> 		 * we split the 64-bit update into two 32-bit writes. In order
>--
>2.7.4