On Wednesday 09 December 2015 01:21:58 Masahiro Yamada wrote: > The UniPhier System Bus is an external that connects on-board devices > to the UniPhier SoC. Each bank (chip select) is dynamically mapped > to the CPU-viewed address base via the bus controller. The bus > controller must be configured before any access to the bus. > > This driver parses the "ranges" property of the System Bus node and > initialized the bus controller. After the bus becomes ready, devices > below it are populated. > > Note: > Each bank can be mapped anywhere in the supported address space; > there is nothing preventing us from assigning bank 0 on 0x42000000, > 0x43000000, or anywhere as long as such region is not used by others. > So, the "ranges" is just one possible software configuration, which > does not seem to fit in device tree because device tree is a hardware > description language. However, of_translate_address() requires > "ranges" in every bus node between CPUs and device mapped on the CPU > address space. In other words, "ranges" properties must be statically > defined in device tree. After some discussion, I decided the dynamic > address reassignment by the driver is too bothersome. Instead, the > device tree should provide a reasonable translation setup that the OS > can rely on. > > Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> > Acked-by: Rob Herring <robh@xxxxxxxxxx> Looks very nice. Acked-by: Arnd Bergmann <arnd@xxxxxxxx> Just a little thought about one thing I found odd: > +static int uniphier_system_bus_check_overlap( > + struct uniphier_system_bus_priv tmp) > +{ Did you intentionally pass this by value? Maybe do it explicitly using a pointer and memcpy to a local variable, which has a similar effect. Alternatively just check each newly probed child node for conflicts with any of the previous children. That is slightly more expensive at O(n^2) instead of O(n) but n is always small here and you can avoid sorting first. Arnd -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html