On Sat, May 01, 2021 at 12:10:16AM +0200, Michael Walle wrote: > Am 2021-04-30 19:26, schrieb Mark Brown: > > But that's a driver for a specific device AFAICT which looks like it's > > only got an I2C binding on the MFD so the driver knows that it's for a > > device that's on a bus that's going to sleep and doesn't need to infer > > anything? This looks like the common case I'd expect where there's no > > variation. > You are right, at the moment this driver only has an I2C binding. But > the idea was that this IP block and driver can be reused behind any > kind of bridge; I2C, SPI or MMIO. Actually, I had the impression Is this actually a way people are building hardware though? > that all you need to do to convert it to MMIO is to replace the > "kontron,sl28cpld" compatible with a "syscon" compatible. But it isn't > that easy. Anyway, the idea is that you don't need to change anything > in the gpio-sl28cpld driver, just change the parent. But if we can't > ask the regmap what type it is, then we'll have to modify the > gpio-sl28cpld driver and we will have to figure it out by some other > means. Well, you don't need to change anything at all - the driver will work perfectly fine if it's flagging up the GPIOs as potentially sleeping even if they end up not actually sleeping. > > If users happen to end up with a map flagged as fast they can work on > > the whatever driver uses this stuff and not realise they're breaking > > other users of the same driver that end up with slow I/O. The whole > > point of the flag in GPIO is AIUI warnings to help with that case. > Hm, but as of now, the only thing which makes the gpio-regmap driver > slow i/o is the regmap itself. Surely it's just a case of the device that's creating the gpio regmap setting a flag when it instantiates it? It's just one more thing that the parent knows about the device. This doesn't seem insurmountable.
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