Visa Question: US Passport Traveling LA → Hong Kong → Chongqing → Shanghai → LA

Hi everyone, I’m planning a trip and could use some advice on visa requirements.

I’m a U.S. citizen flying from Los Angeles → Hong Kong → Chongqing → Shanghai → back to Los Angeles. I’ll only be staying in mainland China (Chongqing and Shanghai) for about 7 days total.

Do I need to apply for a visa in advance, or would I qualify for any visa-free transit policies? Since I’m entering mainland China from Hong Kong, I’m not sure how that affects eligibility.

If anyone has done a similar route or knows the current rules, I’d really appreciate your help. Thanks!