On Sat, Apr 04, 2020 at 07:24:25PM -0600, Rob Herring wrote: > On Fri, Apr 3, 2020 at 12:56 PM Thierry Reding <thierry.reding@xxxxxxxxx> wrote: > > > > From: Thierry Reding <treding@xxxxxxxxxx> > > > > Hi Rob, all, > > > > this is a set of patches that I've been working on to allow me to use > > reserved memory regions more flexibly. One of the use-cases that I have > > is an external memory controller driver that gets passed one or two > > tables from firmware containing a set of EMC frequencies and the > > corresponding register values to program for these frequencies. > > > > One of these tables is the "nominal" table and an optional second table > > is "derated" and is used when the DRAM chips are overheating. I want to > > be able to pass these tables as separate memory-region entries. > > > > So what this small patchset does is make the reserved-memory code adapt > > to this situation better. On one hand, while the DT bindings currently > > support multiple regions per device tree node, it's slightly unintuitive > > to specify them. The first patch adds a memory-region-names property > > that allows the DT to specify a "consumer" name for these regions much > > like we do for things like clocks, resets or the reg property. At the > > same time, a new alias for memory-region, named memory-regions, is > > introduced to make this more consistent with other bindings. > > It's just not worth supporting both flavors (forever). I don't want to > repeat gpio vs. gpios. Let's just stick with 'memory-region' and allow > that to be more than one entry. Alright, I'll drop the corresponding changes from the bindings and the OF core then. > I'm not a fan of *-names, but fine. I suppose I could work without them, but I like the descriptiveness that they add to the device tree. There are also cases where they can be very essential. For example, what if a device can take two separate memory regions. One case that we have on Tegra is the display controller that can have a framebuffer and a color-conversion lookup table assigned to it on boot. I think in this particular case both are actually always there, but what if either of them was optional. Without -names it would be impossible to describe the context if only one is provided in device tree. Thierry
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