Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: What does ISA/PCI really mean to ARM architecture? | Date | Thu, 27 Dec 2012 16:07:23 +0000 |
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On Thursday 27 December 2012, anish kumar wrote: > On Thu, 2012-12-27 at 10:51 +0100, Geert Uytterhoeven wrote: > > On Thu, Dec 27, 2012 at 9:27 AM, Woody Wu <narkewoody@gmail.com> wrote: > > > Can a peripheral chip that claims to be ISA or PCI device be used in a > > > ARM based embedded system? For these kind of chips, I only concern > > > about the planar kind of devices, means they are not on a dedicated > > > expansion card. > > > > > > From hardware point of view, to attach a ISA or PCI planar chip, is > > > there any requirement need to fulfill on a ARM bard? > arm AFAIK is only used in embedded system but ISA/PCI buses are > generally part of 'big systems' and most of the times it refers to x86 > PC.
In the old days, there were a few ARM based systems that were closer to what we think of as a PC, and that had actual ISA slots, or (more commonly) PCMCIA, which is related to ISA.
Aside from that, there are and have been for a long time some ARM systems that have PCI or PCIe slots.
Note that the distinction between ISA-style platform devices and ISA add-on cards is a little fuzzy. The Kconfig option CONFIG_ISA refers to the latter, but there are also ARM systems that only have the former, e.g. for floppy controller.
> > > From Linux driver point of view, what are needed to support an ISA or > > > PCI driver in ARM architecture? More important, is ISA or PCI device a > > > platform device? If not, how to add these kind of devices in my board > > > definition? > > AFAIK, Platform device is just a way to add a particular driver whose > probe can't be called at runtime. Mostly platform device is part of > system on chip.
Right. Note that some ISA devices (especially those that are typically on-board) are platform devices as well, but PCI devices never are.
> > An ISA device is typically a platform device. For ARM, which uses device trees, > Don't know much about ISA device to comment on this but people familiar > with this can enlighten us as to the reason why it is platform device in > detail.
Classic ISA has no way to probe the presence of a device, so platform devices were introduced to handle those. There is also ISAPNP, which adds PCI-like probing on top of ISA, but most ISA cards precede that standard.
Arnd
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