On Thursday 27 February 2014 16:20:03 Liviu Dudau wrote: > On Thu, Feb 27, 2014 at 03:58:41PM +0000, Arnd Bergmann wrote: > > On Thursday 27 February 2014 14:13:22 Liviu Dudau wrote: > > > > > > It is useful for host bridge drivers as this is the only place where we store > > > the physical CPU address for the IO range. This is then needed when setting up the > > > translation registers. Also used when calling the pci_ioremap_io function that I'm > > > introducing in the AArch64 patches. > > > > I don't understand what translation windows you are talking about. Is this > > about how the PCI spaces are mapped into the CPU address space? If so, I > > would strongly recommend to have this handled by the boot loader before > > calling into the kernel. For ARM32, we have a lot of embedded systems > > that require the PCI host driver to set up those windows, but actually > > it would be much better to just have the firmware tell us what the setup > > is and that use that. > > The AXI to PCI bridge that I'm using has a set of registers for doing address translation. > When it sees an AXI translation that matches the programmed translation window will > convert it into a PCI write using the PCI address base written in that translation window. > In other words you basically program the DT range into those address translation registers > and the bridge does the AXI to PCI conversion for you. Right. That should definitely be done in the boot loader before Linux is started. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
