On Wed, Apr 16, 2014 at 10:24 PM, Alexander Graf <ag...@suse.de> wrote: > > On 15.04.14 04:21, Peter Crosthwaite wrote: >> >> Add a sysbus device consisting of a single ram. This allows for >> instantiation of RAM just like any other device. There are a number >> of good reasons to want to do this this: >> >> 1: Consistency. RAM is not that special where board level files should >> have to instantiate it with a completely different API. This reduces >> complexity of board level development by hiding the memory API >> completely and handling everything via the sysbus API. >> >> 2: Device tree completeness. Ram Now shows up in info-qtree and >> friends. E.g. Info qtree gives meaningful information under the >> root system bus: >> >> dev: sysbus-memory, id "zynq.ocm_ram" >> size = 262144 (0x40000) >> read-only = false >> irq 0 >> mmio 00000000fffc0000/0000000000040000 >> dev: sysbus-memory, id "zynq.ext_ram" >> size = 134217728 (0x8000000) >> read-only = false >> irq 0 >> mmio 0000000000000000/0000000008000000 >> >> 3: Remove dependence of global state. Board files don't have to >> explicity request the global singleton (and much unloved) >> address_space_memory() and go hacking on it. address_space_memory() >> is still ultimately used, but the ugliness is hidden in one place - the >> sysbus core (we can fix that another day). >> >> 4: Data driven machine creation. There is list discussion on being able >> to create or append-to sysbus machines in a data-driven way (whether >> thats from command-line, monitor or scripts or whatever). This patch >> removes the memory special case from that problem and allows RAM >> instantiation to come via whatever solutions we come up with sysbus >> device instantiation. >> >> Signed-off-by: Peter Crosthwaite <peter.crosthwa...@xilinx.com> > > > Could you please show that this approach works for more complicated > machines, like x86's pc machine and its PCI holes? >
Hi Alex, Do you mean attaching it within a PCI address space? Im not sure that's valid. That would require some sort of generalisation that applied to both sysbus and PCI. I actually had a go at something like this a while back. Basically, the setup was for PCI devices to inherit from sysbus. This allowed solving the reverse problem. Attaching a PCI device to sysbus. I guess with a few changes it could be made to work both ways, but it seems the sysbus and PC world are completely separate the way the tree stands today. Regards, Peter > > Alex > >