Re: [PATCH V4 3/4] ACPI/IORT: Ignore all errors except EPROBE_DEFER

Sricharan R
2017-05-22T11:06:06Z

Hi Lorenzo,

On 5/22/2017 4:07 PM, Lorenzo Pieralisi wrote:
> Hi Sricharan,
>
> On Thu, May 18, 2017 at 08:24:16PM +0530, 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.
>>
>> Fixes: 5a1bb638d567 ("drivers: acpi: Handle IOMMU lookup failure with deferred probing or error")
>> Signed-off-by: Sricharan R <sricharan@codeaurora.org>
>> ---
>> [V4] Added this patch newly.
>>
>> drivers/acpi/arm64/iort.c | 6 ++++++
>> 1 file changed, 6 insertions(+)
>>
>> 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;
>> }
>>
>
> It is getting a bit convoluted. Is not it better to propagate the
> error back and let acpi_dma_configure() make a decision accordingly ?
>

ok, I was trying to keep it in same way as DT, where of_dma_configure
(here acpi_dma_configure) calls of_iommu_configure(here iort_iommu_configure)
which ends up doing the check. So will have to be changed in both places
for symmetry.

> Something like:
>
> -- >8 --
> 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;

In case of other errors apart from EPROBE_DEFER,
iommu = NULL should be set, before passing it on to
arch_setup_dma_ops.

Regards,
Sricharan

>
> size = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1);
> /*
>

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