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

Lorenzo Pieralisi
2017-05-22T10:36:34Z

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 ?

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;

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