On 01/16/2014 12:19 PM, Arnd Bergmann wrote: > On Thursday 16 January 2014, Marc C wrote: >>> And then you can add a regular device driver to drivers/reset that provides a >>> device_reset() API to other drivers, or a system-reset function to be registered as >>> arm_pm_restart. This driver would use syscon_regmap_lookup_by_phandle() to get access >>> to a regmap pointer, and then use either hardcoded offsets into the regmap, or get >>> those offsets from numbers in the devicetree, as provided in the example above. >> >> I was able to port a standalone "reboot" driver using syscon + regmap. However, for the >> SMP initialization case, it turns out that syscon is configured after SMP init. Do you >> have any advice for this type of situation? >> >> I'd hate to go around in circles, but without resorting to hard-coded offsets, perhaps I >> can just add the remaining "non-regmap" register offsets in the DT? > > You are not the first one to stumble over this problem. There are > two ways to get out of it, and we should probably implement both in > the long run: > > 1. Other platforms also require the syscon driver to be active before > the regular device driver probing starts. Michal Simek has the same > issue in the zynq clock driver that you have for SMP initialization. > We have talked about this with Mark Brown already, and I think we will > find a solution for this in the end, but it's not as straightforward > as I first hoped. We can probably use help in this area. I wouldn't say issue because we have created workaround which should be acceptable. For more info. https://lkml.org/lkml/2014/1/6/349 patch 2/7 is that what we have done to get it work. Also I hope that this can go to mainline before any nice solution will be find not to stop work on others drivers which use regmap. But there is definitely a space for doing this better. > 2. There is actually no reason for the SMP code to be called this early, > and multiple platforms would like to move SMP init to a later stage. > Stephen Boyd has recently started reworking the way we do SMP init, > and he may have some more insight. > > In the meantime, I'd suggest you do the binding under the assumption > that it will work eventually, and then work around the current limitations > in the SMP code by looking for the device nodes you need and map them > manually, as you did in the previous versions of your patch set. Yep, that's exactly what we have done just because of other driver developing till this is resolved. Thanks, Michal -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
