upload product with image, codeigniter

i have problem with uploading data with picture file in it. i can't insert it in db, and can't display the error message. i want to upload the image to my folder assets/images/ , and then upload the data with image url to DB, Please anyone help me.

controller :

public function validate_insert(){
        $this->form_validation->set_rules("namaBarang", "Nama Product", "trim|required|min_length[3]|max_length[100]");
        $this->form_validation->set_rules("hargaBarang", "Harga Product", "trim|required|integer");
        $this->form_validation->set_rules("deskripsiBarang", "Deskripsi Product", "trim|required|min_length[20]|max_length[10000]");
        $this->form_validation->set_rules("categoryBarang", "Category Product", "trim|required");
        $this->form_validation->set_rules("tipeBarang", "Tipe Product", "trim|required|min_length[3]|max_length[100]");
        $this->form_validation->set_rules("merkBarang", "Merk Product", "trim|required");
        $this->form_validation->set_rules("gambarBarang", "Gambar Product", "trim");


        if($this->form_validation->run()){

            $path = './assets/images/';
            chmod($path, 0777);
            $config['upload_path'] = $path;
            $config['allowed_types'] = 'gif|jpg|png|jpeg';
            $config['max_size'] = '6000';
            $config['max_width']  = '1024';
            $config['max_height']  = '768';
            $config['overwrite'] = TRUE;
            $config["remove_spaces"] = TRUE;

            $this->load->library("upload", $config);

            if(!$this->upload->do_upload()){
                $uploadError = array("upload_error" => $this->upload->display_errors());
                //$this->session->set_flashdata("uploadError", $uploadError, "adminFolder/admin/insertPicture");
                //redirect("adminFolder/admin/insertProduct");
            }else{
                $file_info = $this->upload->data("userfile");
                $file_name = $file_info["file_name"];

                $newInsert = array(
                        "nama" => $this->input->post("namaBarang"),
                        "deskripsi" => $this->input->post("deskripsiBarang"),
                        "harga" => $this->input->post("hargaBarang"),
                        "gambar" => $file_name,
                        "tipe" => $this->input->post("tipeBarang"),
                        "merk" => $this->input->post("merkBarang"),
                        "category" => $this->input->post("categoryBarang")
                );

                $this->model_get->insertProduct($newInsert);
                redirect("adminFolder/admin/adminProduct");

            }

        }else{
            $this->form_validation->set_message("required", "harus diisi !!!");
            $this->insertProduct();
        }
    }

This Is the Controller that calling the View below :

public function insertProduct(){
        $data["categories"] = $this->getCategory();
        $data["merk"] = $this->getMerk();

        $this->adminHeader();
        $this->load->view("adminPages/insertProduct", $data);
        $this->adminFooter();
    }

My View :

<div id="subMenu">


        </div>

        <div id="content">

            <?php 
                foreach ($categories as $category){
                    $dataCat[$category->category] = $category->category;
                }

                foreach ($merk as $mrk){
                    $dataMerk[$mrk->merk] = $mrk->merk;
                }

                echo form_open("adminFolder/admin/validate_insert");

                if(isset($upload_error)){
                    echo $upload_error;
                }

                echo validation_errors();

                echo "<p>Nama Barang = ";
                echo form_input("namaBarang");
                echo "</p>";

                echo "<p>Harga Barang = ";
                echo form_input("hargaBarang");
                echo "</p>";

                echo "<p>Deskripsi Barang = ";
                echo form_textarea("deskripsiBarang");
                echo "</p>";

                echo "<p>Category Barang = ";
                echo form_dropdown("categoryBarang", $dataCat);
                //echo form_input("categoryBarang");
                echo "</p>";

                echo "<p>Merk Barang = ";
                echo form_dropdown("merkBarang", $dataMerk);
                //echo form_input("merkBarang");
                echo "</p>";

                echo "<p>Tipe Barang = ";
                echo form_input("tipeBarang");
                echo "</p>";

                echo "<p>Gambar Barang = ";
                echo form_upload("gambarBarang", "Gambar Barang");
                echo "</p>";

                echo form_submit("insert_submit", "Insert Product");
            ?>

        </div>

My Model :

function insertProduct($data){
        $insert = $this->db->insert("barang", $data);
    }