IB/mlx5: Mmap the HCA's core clock register to user-space

In order to read the HCA's current cycles register, we need
to map it to user-space. Add support to map this register
via mmap command.
Signed-off-by: Matan Barak <matanb@mellanox.com>
Reviewed-by: Moshe Lazer <moshel@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/mlx5/main.c

@@ -1023,6 +1023,34 @@ static int mlx5_ib_mmap(struct ib_ucontext *ibcontext, struct vm_area_struct *vm
 	case MLX5_IB_MMAP_GET_CONTIGUOUS_PAGES:
 		return -ENOSYS;
 
+	case MLX5_IB_MMAP_CORE_CLOCK:
+	{
+		phys_addr_t pfn;
+
+		if (vma->vm_end - vma->vm_start != PAGE_SIZE)
+			return -EINVAL;
+
+		if (vma->vm_flags & (VM_WRITE | VM_EXEC))
+			return -EPERM;
+
+		/* Don't expose to user-space information it shouldn't have */
+		if (PAGE_SIZE > 4096)
+			return -EOPNOTSUPP;
+
+		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+		pfn = (dev->mdev->iseg_base +
+		       offsetof(struct mlx5_init_seg, internal_timer_h)) >>
+			PAGE_SHIFT;
+		if (io_remap_pfn_range(vma, vma->vm_start, pfn,
+				       PAGE_SIZE, vma->vm_page_prot))
+			return -EAGAIN;
+
+		mlx5_ib_dbg(dev, "mapped internal timer at 0x%lx, PA 0x%llx\n",
+			    vma->vm_start,
+			    (unsigned long long)pfn << PAGE_SHIFT);
+		break;
+	}
+
 	default:
 		return -EINVAL;
 	}

drivers/infiniband/hw/mlx5/mlx5_ib.h

@@ -65,7 +65,9 @@ enum {
 
 enum mlx5_ib_mmap_cmd {
 	MLX5_IB_MMAP_REGULAR_PAGE		= 0,
-	MLX5_IB_MMAP_GET_CONTIGUOUS_PAGES	= 1, /* always last */
+	MLX5_IB_MMAP_GET_CONTIGUOUS_PAGES	= 1,
+	/* 5 is chosen in order to be compatible with old versions of libmlx5 */
+	MLX5_IB_MMAP_CORE_CLOCK			= 5,
 };
 
 enum {