Re: [PATCH] ARC: IOC: panic if kernel was started with previously enabled IOC

From: Vineet Gupta
Date: Tue Oct 16 2018 - 13:27:40 EST

On 10/04/2018 06:12 AM, Eugeniy Paltsev wrote:
> Disabling and reconfiguring of IOC are quite a tricky actions because
> nobody knows what happens if there're IOC-ahndled tarnsactions in flight
> when we're disabling IOC.
> And the problem is external DMA masters [that were initialized and set
> in a bootlaoder that was executed before we got here] might continue
> to send data to memory even at this point and we have no way to prevent
> that.
> That said it's much safer to not enable IOC at all anywhere before Linux
> kernel.
> As we can build u-boot with IOC support (mostly for debugging purposes)
> let's check that kernel was started with disabled IOC regardless of
> our plans to use it or not.
> Also while I'm at it, replace hardcoded bits in ARC_REG_IO_COH_PARTIAL
> and ARC_REG_IO_COH_ENABLE registers by definitions.
> Inspired by:

Applied with updated changelog !