Re: 32-bit accesses to mtime/mtimecmp under RV64
Andrew Waterman
On Fri, Apr 17, 2020 at 7:00 PM Greg Favor <gfavor@...> wrote:
The spec strongly implies by omission that 64-bit accesses are atomic for RV64, in that it gives an unusually detailed RV32-specific code example to cope with non-atomicity, but mentions nothing of the sort for RV64. I will add the additional sentence that makes this implication explicit.
In general, this depends on the peripheral and the platform. We aren't trying to preclude interfacing with legacy devices and buses, so of course some 64-bit accesses to some devices will either become non-atomic or signal some sort of error. But it's really quite useful to be able to assume that 64-bit accesses are atomic when interfacing with more modern peripherals that use 64-bit addresses, so we definitely do not want to preclude that, either.
|
|