Messages in this thread | | | Subject | Re: simple-reset to de-duplicate reset drivers | From | Philipp Zabel <> | Date | Fri, 11 Aug 2017 10:19:50 +0200 |
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Hi Alexandru,
On Thu, 2017-08-10 at 17:16 -0700, Alexandru Gagniuc wrote: > Hi, > > I was looking at implementing a reset driver for our in-house SoC. > It's > essentially a long bitfield, each bit controlling one sort of reset. > That seems to be surprisingly common. I've identified the following > drivers which control a very similar reset: > > * reset-zynq > * reset-zx2967 > * reset-sunxi > * reset-stm32 > * reset-socfpga > * reset-oxynas > * reset-meson > * reset-berlin
I think zx2967, sunxi, stm32, and socfpga could be unified using common ops.
zynq, oxnas, and berlin are special because they use regmap to access shared syscon register space, or have special delays, or both. meson is different because the resets are self-clearing. It doesn't implement assert/deassert at all.
> All of these have in common some form of another of: > > int bank = id / BITS_PER_LONG; > int offset = id % BITS_PER_LONG; > > It doesn't make sense to me why all these would be duplicated for every > reset controller. I think it would make sense to have a common driver to > handle these simple resets -- call it "simple-reset". I'm thinking of > something similar to drivers/tty/serial/8250, where the following > parameters can be specified: > > - reg-offset > - reg-shift > - reg-io-width
Drivers have to keep working with the existing, documented bindings, so we can't introduce new required device tree properties for them. That being said, adding optional properties with documented defaults that fit the current drivers should be possible.
> I think a generic "simple-reset" driver which is configurable by a > similar set of parameters would be a suitable replacement for all the > aforementioned drivers. As far as our SoC goes, I've just added > > compatible = "st,stm32-rcc"; > > to our devicetree, and I already have a fully-working reset driver. Do > you think we should proceed in the direction of "simple-reset", and what > other features do you estimate we'll need?
Another difference between the simple reset controllers is whether the bits are set to assert or cleared to assert.
Even without touching device trees, we can share the backend code by providing common ops to use for all compatible drivers, and we could also merge them into a single driver that determines the parameters from the compatible string.
What do you think about this previous attempt to unify sunxi, stm32, and socfpga:
https://patchwork.kernel.org/patch/9610709/
regards Philipp
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