linux-kernel - Re: [PATCH] iommu/exynos: Get rid of 'struct exynos_iommu_owner' exynos_iommu

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Date:   Thu, 9 Apr 2020 16:30:59 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rob Clark <robdclark@...il.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-tegra@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH] iommu/exynos: Get rid of 'struct exynos_iommu_owner'
 exynos_iommu_owner

Hi Marek,

On Thu, Apr 09, 2020 at 03:58:00PM +0200, Marek Szyprowski wrote:
> The main problem after your conversion is the fact that ->probe_device() 
> is called very early, before any other platform device (thus IOMMU 
> controller) is is probed. It doesn't handle EPROBE_DEFER too.

I don't quite understand why probe_device() is called too early, as it
is called at the same time add_device() was called before. But anyway,
I have seen a similar problem on OMAP. If the SYSMMU for a master is not
probed yet when probe_device() is called, it can just return -ENODEV and
in your driver you just call but_iommu_probe() when a new SYSMMU got
initialized to re-probe uninitialized masters on the bus. This patch-set
contains a change to export bus_iommu_probe() for exactly that reason.

What do you think?

Regards,

	Joerg