linux-kernel - Re: [PATCH v6 3/6] ACPI/IORT: Ignore all errors except EPROBE

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Message-ID: <1564836.5iBbgoacpH@aspire.rjw.lan>
Date:   Sat, 27 May 2017 21:18:39 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Sricharan R <sricharan@...eaurora.org>
Cc:     robin.murphy@....com, will.deacon@....com, joro@...tes.org,
        lorenzo.pieralisi@....com, iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, m.szyprowski@...sung.com,
        bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-acpi@...r.kernel.org, tn@...ihalf.com, hanjun.guo@...aro.org,
        okaya@...eaurora.org, robh+dt@...nel.org, frowand.list@...il.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        sudeep.holla@....com, lenb@...nel.org, catalin.marinas@....com,
        arnd@...db.de, linux-arch@...r.kernel.org,
        laurent.pinchart@...asonboard.com, j.neuschaefer@....net,
        geert@...ux-m68k.org, magnus.damm@...il.com,
        nwatters@...eaurora.org, linux@...linux.org.uk
Subject: Re: [PATCH v6 3/6] ACPI/IORT: Ignore all errors except EPROBE_DEFER

On Saturday, May 27, 2017 07:17:42 PM Sricharan R wrote:
> While deferring the probe of IOMMU masters, xlate and
> add_device callbacks called from iort_iommu_configure
> can pass back error values like -ENODEV, which means
> the IOMMU cannot be connected with that master for real
> reasons. Before the IOMMU probe deferral, all such errors
> were ignored. Now all those errors are propagated back,
> killing the master's probe for such errors. Instead ignore
> all the errors except EPROBE_DEFER, which is the only one
> of concern and let the master work without IOMMU, thus
> restoring the old behavior. Also make explicit that
> acpi_dma_configure handles only -EPROBE_DEFER from
> iort_iommu_configure.
> 
> Fixes: 5a1bb638d567 ("drivers: acpi: Handle IOMMU lookup failure with deferred probing or error")
> Signed-off-by: Sricharan R <sricharan@...eaurora.org>
> ---
>  drivers/acpi/arm64/iort.c | 6 ++++++
>  drivers/acpi/scan.c       | 4 ++--
>  2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index c5fecf9..16e101f 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c
> @@ -782,6 +782,12 @@ const struct iommu_ops *iort_iommu_configure(struct device *dev)
>  	if (err)
>  		ops = ERR_PTR(err);
>  
> +	/* Ignore all other errors apart from EPROBE_DEFER */
> +	if (IS_ERR(ops) && (PTR_ERR(ops) != -EPROBE_DEFER)) {
> +		dev_dbg(dev, "Adding to IOMMU failed: %ld\n", PTR_ERR(ops));
> +		ops = NULL;
> +	}
> +
>  	return ops;
>  }
>  
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index e39ec7b..3a10d757 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -1371,8 +1371,8 @@ int acpi_dma_configure(struct device *dev, enum dev_dma_attr attr)
>  	iort_set_dma_mask(dev);
>  
>  	iommu = iort_iommu_configure(dev);
> -	if (IS_ERR(iommu))
> -		return PTR_ERR(iommu);
> +	if (IS_ERR(iommu) && PTR_ERR(iommu) == -EPROBE_DEFER)
> +		return -EPROBE_DEFER;
>  
>  	size = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1);
>  	/*
> 

ACK for the scan.c change and I'm assuming this to go in via ARM64.

Thanks,
Rafael