linux-kernel - Re: [RFC] iommu: arm-smmu: stall support

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Date:   Wed, 27 Sep 2017 14:15:40 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Rob Clark <robdclark@...il.com>
Cc:     Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Will Deacon <Will.Deacon@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC] iommu: arm-smmu: stall support

Hi Rob, Jean,

On Fri, Sep 22, 2017 at 02:42:44PM -0400, Rob Clark wrote:
> I'm in favour if splitting the reporting *somehow*.. the two
> approaches that seemed sane are:
> 
> 1) call fault handler from irq and having separate domain->resume()
> called by the driver, potentially from a wq
> 2) or having two fault callbacks, first called before wq and then
> based on returned value, optionally 2nd callback called from wq
> 
> The first seemed less intrusive to me, but I'm flexible.

How about adding a flag to the fault-handler call-back that tells us
whether it wants to sleep or not. If it wants, we call it from a wq, if
not we call call it directly like we do today in the
report_iommu_fault() function.

In any case we call iommu_ops->resume() when set on completion of the
fault-handler either from the workqueue or report_iommu_fault itself.


Regards,

	Joerg