linux-kernel - Re: [PATCH V11 08/11] drivers: acpi: Handle IOMMU lookup failure with deferred probing or error

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Date:   Tue, 23 May 2017 09:52:41 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Nate Watterson <nwatters@...eaurora.org>
Cc:     Sricharan R <sricharan@...eaurora.org>, robin.murphy@....com,
        will.deacon@....com, joro@...tes.org,
        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, rjw@...ysocki.net, lenb@...nel.org,
        catalin.marinas@....com, arnd@...db.de, linux-arch@...r.kernel.org,
        gregkh@...uxfoundation.org
Subject: Re: [PATCH V11 08/11] drivers: acpi: Handle IOMMU lookup failure
 with deferred probing or error

On Tue, May 23, 2017 at 02:26:10AM -0400, Nate Watterson wrote:
> Hi Sricharan,
> 
> On 4/10/2017 7:21 AM, Sricharan R wrote:
> >This is an equivalent to the DT's handling of the iommu master's probe
> >with deferred probing when the corrsponding iommu is not probed yet.
> >The lack of a registered IOMMU can be caused by the lack of a driver for
> >the IOMMU, the IOMMU device probe not having been performed yet, having
> >been deferred, or having failed.
> >
> >The first case occurs when the firmware describes the bus master and
> >IOMMU topology correctly but no device driver exists for the IOMMU yet
> >or the device driver has not been compiled in. Return NULL, the caller
> >will configure the device without an IOMMU.
> >
> >The second and third cases are handled by deferring the probe of the bus
> >master device which will eventually get reprobed after the IOMMU.
> >
> >The last case is currently handled by deferring the probe of the bus
> >master device as well. A mechanism to either configure the bus master
> >device without an IOMMU or to fail the bus master device probe depending
> >on whether the IOMMU is optional or mandatory would be a good
> >enhancement.
> >
> >Tested-by: Hanjun Guo <hanjun.guo@...aro.org>
> >Reviewed-by: Robin Murphy <robin.murphy@....com>
> >[Lorenzo: Added fixes for dma_coherent_mask overflow, acpi_dma_configure
> >           called multiple times for same device]
> >Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> >Signed-off-by: Sricharan R <sricharan@...eaurora.org>
> >---
> >  drivers/acpi/arm64/iort.c  | 33 ++++++++++++++++++++++++++++++++-
> >  drivers/acpi/scan.c        | 11 ++++++++---
> >  drivers/base/dma-mapping.c |  2 +-
> >  include/acpi/acpi_bus.h    |  2 +-
> >  include/linux/acpi.h       |  7 +++++--
> >  5 files changed, 47 insertions(+), 8 deletions(-)
> >
> >diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> >index 3dd9ec3..e323ece 100644
> >--- a/drivers/acpi/arm64/iort.c
> >+++ b/drivers/acpi/arm64/iort.c
> >@@ -543,6 +543,14 @@ static const struct iommu_ops *iort_iommu_xlate(struct device *dev,
> >  	const struct iommu_ops *ops = NULL;
> >  	int ret = -ENODEV;
> >  	struct fwnode_handle *iort_fwnode;
> >+	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
> >+
> >+	/*
> >+	 * If we already translated the fwspec there
> >+	 * is nothing left to do, return the iommu_ops.
> >+	 */
> >+	if (fwspec && fwspec->ops)
> >+		return fwspec->ops;
> 
> Is this logic strictly required? It breaks masters with multiple SIDs
> as only the first SID is actually added to the master's fwspec.

My bad, that's indeed a silly bug I introduced. Please let me know if the
patch below fixes it, we will send it upstream shortly.

Lorenzo

-- >8 --
diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index c5fecf9..e326f2a 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c
@@ -666,14 +666,6 @@ static const struct iommu_ops *iort_iommu_xlate(struct device *dev,
 	int ret = -ENODEV;
 	struct fwnode_handle *iort_fwnode;
 
-	/*
-	 * If we already translated the fwspec there
-	 * is nothing left to do, return the iommu_ops.
-	 */
-	ops = iort_fwspec_iommu_ops(dev->iommu_fwspec);
-	if (ops)
-		return ops;
-
 	if (node) {
 		iort_fwnode = iort_get_fwnode(node);
 		if (!iort_fwnode)
@@ -735,6 +727,14 @@ const struct iommu_ops *iort_iommu_configure(struct device *dev)
 	u32 streamid = 0;
 	int err;
 
+	/*
+	 * If we already translated the fwspec there
+	 * is nothing left to do, return the iommu_ops.
+	 */
+	ops = iort_fwspec_iommu_ops(dev->iommu_fwspec);
+	if (ops)
+		return ops;
+
 	if (dev_is_pci(dev)) {
 		struct pci_bus *bus = to_pci_dev(dev)->bus;
 		u32 rid;