On Mon, Jul 30, 2018, 2:27 PM Amaan Cheval <amaan.che...@gmail.com> wrote:
> Quick status update: in working on the APIC timer, as a prerequisite, > I've had to setup access to the Interrupt Descriptor Table (which is > great because it helps us have the basic interrupt support we need at > least). > > Another minor issue I've run into is the fact that the APIC is located > at physical address 0xfee00000 by default on most x86 processors - per > the FreeBSD bootloader's paging scheme, they map every GiB of virtual > memory to the first 1 GiB of physical memory (0x40000000). > > As a workaround, I'll probably just move the APIC address to within > this accessible range (through a Model Specific Register) with an > "XXX" comment about creating a better paging scheme later. > > Let me know if anyone thinks better paging support should also come > first! If not, what's next is initializing the PIT to calibrate the > APIC timer, and then we should have a pretty nice and self-contained > clock driver for the x86_64 port too. > Make the clock tick and timer driver work first. Will this have any impact on the amount of RAM accessible until this is fixed? > > On Wed, Jul 18, 2018 at 7:53 PM, Gedare Bloom <ged...@rtems.org> wrote: > > On Wed, Jul 18, 2018 at 10:17 AM, Joel Sherrill <j...@rtems.org> wrote: > >> > >> > >> On Wed, Jul 18, 2018 at 12:31 AM, Sebastian Huber > >> <sebastian.hu...@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. > >> > > > > I believe he meant ignore hardware that is not available from products > > in the last five years. > > > > > >> 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. > >> > > > > This is consistent with my interpretation. > > > >> --joel > >> > >>> > >>> > >>> > >>> -- > >>> Sebastian Huber, embedded brains GmbH > >>> > >>> Address : Dornierstr. 4, D-82178 Puchheim, Germany > >>> Phone : +49 89 189 47 41-16 > >>> Fax : +49 89 189 47 41-09 > >>> E-Mail : sebastian.hu...@embedded-brains.de > >>> PGP : Public key available on request. > >>> > >>> Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG. > >>> > >> >
_______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel
