Re: MTIME update frequency
On Fri, Nov 19, 2021 at 7:36 AM Darius Rad <darius@...> wrote:
The current requirement effectively forces implementations to have a 100
The resolution requirement (whether =10ns or <=10ns) doesn't force a 100 or 100+ MHz clock. Only the >=10 MHz update rate forces a 10 MHz clock - which is a pretty modest requirement for OS-A-class systems. (As a side-note, most any DDR interface or high-speed I/O interface (e.g. USB, SATA, PCIe/NVMe) will want significant clock frequencies supplied to them.)
Either way, this violates
Platforms shouldn't mandate specific software execution performance requirements, but a platform spec may - in the interest of ensuring functionality doesn't have horrible performance - choose to mandate certain qualitative things. For example, a more application domain-targeted platform may choose to disallow trapping and emulating of all misaligned data accesses. (The "Embedded" platform, as a rather basic very "broad" platform, doesn't do this.)
In contrast, mandating that a system has certain hardware capabilities, like a RISC-V standard interrupt controller with at least X number of priorities, or time with some minimum resolution and update rate, is ensuring a form of functionality. For example, an Automotive or Mobile platform may be unhappy if the update rate and resolution are only 10 ms / 100 Hz.