drm/amdgpu: simplify allocation of scratch regs

The scratch regs are sequential so there's no need to keep
them in an array, we can just return the index of the first
free register + the base register. Also change the array
of bools for keeping track of the free regs to a bitfield.

Reviewed-by: Christian König <[e-mail]>
Signed-off-by: Nils Wallménius <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu.h

···
 struct amdgpu_scratch {
 	unsigned		num_reg;
 	uint32_t                reg_base;
-	bool			free[32];
-	uint32_t		reg[32];
+	uint32_t		free_mask;
 };
 
 /*

drivers/gpu/drm/amd/amdgpu/amdgpu_gfx.c

···
 {
 	int i;
 
-	for (i = 0; i < adev->gfx.scratch.num_reg; i++) {
-		if (adev->gfx.scratch.free[i]) {
-			adev->gfx.scratch.free[i] = false;
-			*reg = adev->gfx.scratch.reg[i];
-			return 0;
-		}
+	i = ffs(adev->gfx.scratch.free_mask);
+	if (i != 0 && i <= adev->gfx.scratch.num_reg) {
+		i--;
+		adev->gfx.scratch.free_mask &= ~(1u << i);
+		*reg = adev->gfx.scratch.reg_base + i;
+		return 0;
 	}
 	return -EINVAL;
 }
···
  */
 void amdgpu_gfx_scratch_free(struct amdgpu_device *adev, uint32_t reg)
 {
-	int i;
-
-	for (i = 0; i < adev->gfx.scratch.num_reg; i++) {
-		if (adev->gfx.scratch.reg[i] == reg) {
-			adev->gfx.scratch.free[i] = true;
-			return;
-		}
-	}
+	adev->gfx.scratch.free_mask |= 1u << (reg - adev->gfx.scratch.reg_base);
 }
 
 /**

drivers/gpu/drm/amd/amdgpu/gfx_v6_0.c

···
 
 static void gfx_v6_0_scratch_init(struct amdgpu_device *adev)
 {
-	int i;
-
 	adev->gfx.scratch.num_reg = 7;
 	adev->gfx.scratch.reg_base = mmSCRATCH_REG0;
-	for (i = 0; i < adev->gfx.scratch.num_reg; i++) {
-		adev->gfx.scratch.free[i] = true;
-		adev->gfx.scratch.reg[i] = adev->gfx.scratch.reg_base + i;
-	}
+	adev->gfx.scratch.free_mask = (1u << adev->gfx.scratch.num_reg) - 1;
 }
 
 static int gfx_v6_0_ring_test_ring(struct amdgpu_ring *ring)

drivers/gpu/drm/amd/amdgpu/gfx_v7_0.c

···
  */
 static void gfx_v7_0_scratch_init(struct amdgpu_device *adev)
 {
-	int i;
-
 	adev->gfx.scratch.num_reg = 7;
 	adev->gfx.scratch.reg_base = mmSCRATCH_REG0;
-	for (i = 0; i < adev->gfx.scratch.num_reg; i++) {
-		adev->gfx.scratch.free[i] = true;
-		adev->gfx.scratch.reg[i] = adev->gfx.scratch.reg_base + i;
-	}
+	adev->gfx.scratch.free_mask = (1u << adev->gfx.scratch.num_reg) - 1;
 }
 
 /**

drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c

···
 
 static void gfx_v8_0_scratch_init(struct amdgpu_device *adev)
 {
-	int i;
-
 	adev->gfx.scratch.num_reg = 7;
 	adev->gfx.scratch.reg_base = mmSCRATCH_REG0;
-	for (i = 0; i < adev->gfx.scratch.num_reg; i++) {
-		adev->gfx.scratch.free[i] = true;
-		adev->gfx.scratch.reg[i] = adev->gfx.scratch.reg_base + i;
-	}
+	adev->gfx.scratch.free_mask = (1u << adev->gfx.scratch.num_reg) - 1;
 }
 
 static int gfx_v8_0_ring_test_ring(struct amdgpu_ring *ring)