Can I get the 144hours visa twice? Shanghai-HK-Shanghai

Hi, I'm flying from The UK to Shanghai in November, for a week. I'm staying 2 days and half in Shanghai, and then take the overnight train to Hong Kong, stay in HK 3 days and come back to Shanghai for more 1 day and half as I have my return flight from Shanghai.
Do I need a Tourist visa, or can I get the 144hours visa-free twice, i.e, The entry when I come from the UK to mainland China, and when I'm returning from HK to mainland China? Many thanks.