Once in your lifetime, you can make a funding distribution from an IRA to an HSA. That funding distribution is still limited to your own annual limit (which depends on the type of insurance your have).
After you use up your once in a lifetime funding opportunity, you would have to withdraw from the IRA, pay the tax, and make a deposit into the HSA and take the tax deduction. Most of the time, this will be a wash, so it's still basically "tax free" but you can only do the direct funding route one time.