Messages in this thread | | | Date | Fri, 23 Jul 2021 17:41:58 +0100 | From | Mark Brown <> | Subject | Re: [PATCH 2/3] syscon: add support for "syscon-smc" compatible |
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On Fri, Jul 23, 2021 at 06:07:44PM +0200, Arnd Bergmann wrote:
> There is also a problem with locking: In the case that both firmware and > kernel have to access registers within a syscon area, you may need to > have a semaphore to protect an atomic sequence of accesses, but since > the interface only provides a single register load/store, there is no way for > a kernel driver to serialize against a firmware-internal driver.
The standard solution to this for the read/modify/write case would be to expose an explicit update_bits() operation (some hardware does this for concurrency and/or bus bandwidth/latency reasons), though that doesn't help with larger or multi-register sequences (and to be clear as I've been saying I don't think we should do this at all). [unhandled content-type:application/pgp-signature] | |