[GSoC - x86_64] Clock driver - which hardware source to support primarily?

[Joel Sherrill]

On Wed, Jul 18, 2018 at 12:31 AM, Sebastian Huber <
sebastian.huber at embedded-brains.de> wrote:

> Hello Amaan,
>
> On 17/07/18 19:18, Amaan Cheval wrote:
>
>> Hi!
>>
>> Now that I'm working on the clock driver, we need to pick what we
>> support first. Our options in brief are:
>>
>
> The clock driver needs an interrupt. What is the status of the interrupt
> controller support in the BSP?
>
> For timekeeping we use a port of the FreeBSD timecounter in RTEMS. You may
> have a look at the FreeBSD timecounter for this architecture, e.g.
> sys/x86/x86/tsc.c. I looks quite complicated. I would not take to much care
> about legacy support, e.g. ignore hardware which is older than five years?.


That's not a good rule for PCs at all. The APIC was first introduced as an
external controller with the i486,
Based on your rule, we wouldn't support it even though it is the most
likely choice.

Avoid things that are deemed legacy. The starting point for this is the old
PC
System Design Guide.

https://en.wikipedia.org/wiki/PC_System_Design_Guide

If it was deemed obsolete in PC2001, then you definitely want to avoid it.
Those
things are just now really disappearing.

--joel


>
>
> --
> Sebastian Huber, embedded brains GmbH
>
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