On Tue, Jun 12, 2018 at 4:53 PM, Benjamin Herrenschmidt <b...@kernel.crashing.org> wrote: > On Tue, 2018-06-12 at 11:42 -0600, Rob Herring wrote: >> On Mon, Jun 11, 2018 at 6:01 PM, Benjamin Herrenschmidt >> <b...@kernel.crashing.org> wrote: >> > There are still quite a few cases where a device might want to get to a >> > different node of the device-tree, obtain the resources and map them. >> > >> > Drivers doing that currently open code the whole thing, which is error >> > proe. >> > >> > We have of_iomap() and of_io_request_and_map() but they both have >> > shortcomings, >> > such as not returning the size of the resource found (which can be >> > necessary) >> > and not being "managed". >> > >> > This adds a devm_of_iomap() that provides all of these and should probably >> > replace uses of the above in most drivers. >> > >> > Signed-off-by: Benjamin Herrenschmidt <b...@kernel.crashing.org> >> > --- >> > >> > I'm cooking a driver that uses this, if there's no objection I'd like >> > to carry it in my pull request for that driver (it can also exist in >> > the DT tree of course). Just let me know. >> >> We generally only use of_iomap when there is no struct device for any >> new driver. Why can't you use devm_ioremap_resource? Is this a >> non-platform bus device? > > This is just a wrapper on devm_ioremap_resource :-) Basically it's a > "fixed" version of of_iomap, that has the devm* management and will > mark the resource busy. > > My thinking was to then replace most of_iomap users with this. > > As for the specific case of the driver I'm cooking, it's a case where > the SoC contains a little coprocessor (a ColdFire even !) alongside the
Wow. Must be the 1 licensee. > main ARM core. I have a driver that offloads the bitbanging of some > GPIOs to it (to implement the FSI bus). I use devm_of_iomap() to map > the registers of the interrupt controller of the coprocessor, it's not > really part of the interrupt tree, it doesn't distribute interrupts to > the ARM or to Linux, it's just a device-node pointed to by a handle. Accessing another processor's interrupt controller. What could go wrong with that. I guess this is fine. There's another problem though. This doesn't work on Sparc because address.c is not built. I'd suggest moving to of/device.c or a new file. > BTW. Another thing that I find a bit annoying is "allocated" reserved- > memory, there's no API to get to it other than via the DMA APIs or a > CMA, which is overkill in a few circumstances (such as the one here > where I just want to dedicate a bit of memory to the coprocessor). > Right now I'm using a fixed reservation (with a reg property) and go to > it "manually" but that somewhat sucks. But that's not really a DT problem. It's a kernel problem if you can't reserve a contiguous range of unmapped pages. But why not just get coherent allocation and ignore that it is mapped. That seems better to me than working around it in DT. Rob
