使用CodeIgniter上传xlsx

I work on a module which convert xlsx to csv and doing some stuff on database, I did it with PHP but now I have to do it with CodeIgniter.

Here is my main issue :

I have some "infinite loading" while pressing upload button, and nothing is happening.

Here is my controller

    public function convert(){

      $config['upload_path'] = FCPATH.'views/admin/traitement_xslx/csv'; 
      $config['allowed_types'] = 'xlsx|csv|xls';
      $config['max_size'] = '1000000000'; 
      $config['overwrite'] = true;
      $config['encrypt_name'] = FALSE;
      $config['remove_spaces'] = TRUE;

      $this->upload->initialize($config);

      if ( ! $this->upload->do_upload('xlsxfile'))
      {
            echo 'no';
      }
      else
      {
            echo 'ok';
      }
    }

And this is my view

  <!DOCTYPE HTML>
   <html>
   <head>
    <meta http-equiv="content-type" content="text/html;charset=utf-8"> 
     <?php echo $redir; ?>    
       <script type="text/javascript">
          function message(){  
            document.getElementById("msg").innerHTML="Conversion<blink>...  </blink>";
             } 

      </script> 
  </head>
      <body >     
        <div id="container" style="display:inline-block;">
            <h3 class="alert" id="msg"><?php echo $alert; ?></h3>  
            <p>Selectionnez un fichier XLSX à convertir et traiter :</p>

            <form action="<?= site_url('admin/Traitement_doublons/convert'); ?>" method="post" enctype="multipart/form-data">

                <input type="file" name="xlsxfile" size="40" />
                <input type="hidden" name="convert">
                <br />
                <br />
                <input type="text" name="throttle" id="throttle" value="0" onkeyup="this.value=this.value.replace(/[^\d]/,\'\')"  size="5"> # de lignes à convertir (0 = No limit) <br />
                <br />
                <input type="submit" class="button" name ="upload"  onClick="message()"  value="Convertir en CSV et traiter" />
            </form>
        </div>


        <div id="container" style="display:inline-block;">
            <h3 class="alert" id="msg"><?php echo $alert2; ?></h3>  
            <p>Où un fichier CSV à seulement traiter :</p>

            <form action="#" method="post" enctype="multipart/form-data">

                <input type="file" name="csvfile" size="40" />
                <input type="hidden" name="convertcsv">
                <br />
                <br />
                <input type="text" name="throttlecsv" id="throttle" value="0" onkeyup="this.value=this.value.replace(/[^\d]/,\'\')"  size="5"> # de lignes à convertir (0 = No limit) <br />
                <br />
                <input type="submit" class="button" name = "uploadcsv"  onClick="message()"  value="Traiter les données" />
            </form>
        </div>
        <div>
            <p><?php if(isset($_SESSION['champs']['total'])){ echo $_SESSION['champs']['total']; }?></p>
            <p><?php if(isset($_SESSION['champs']['inseres'])){ echo $_SESSION['champs']['inseres']; }?></p>
            <p><?php if(isset($_SESSION['champs']['doublons'])){ echo $_SESSION['champs']['doublons']; }?></p>
        </div>
    </body>
</html>

Any ideas ? Thanks

First, check if($_FILES['csvfile']['size'] > 0) , add name to your file $config['file_name'] = $new_name; and then give the name of input file name to your do_upload function if ( ! $this->upload->do_upload('csvfile')).