[PATCH] ACPI/IORT: Make dma masks set-up IORT specific

[Lorenzo Pieralisi]

The introduction of acpi_dma_configure() allows to configure DMA
and related IOMMU for any device that is DMA capable. To achieve
that goal it ensures DMA masks are set-up to sane default values
before proceeding with IOMMU and DMA ops configuration.

On x86/ia64 systems, through acpi_bind_one(), acpi_dma_configure() is
called for every device that has an ACPI companion, in that every device
is considered DMA capable on x86/ia64 systems (ie acpi_get_dma_attr() API),
which has the side effect of initializing dma masks also for
pseudo-devices (eg CPUs and memory nodes) and potentially for devices
whose dma masks were not set-up before the acpi_dma_configure() API was
introduced, which may have noxious side effects.

Therefore, in preparation for IORT firmware specific DMA masks set-up,
wrap the default DMA masks set-up in acpi_dma_configure() inside an IORT
specific wrapper that reverts to a NOP on x86/ia64 systems, restoring the
default expected behaviour on x86/ia64 systems and keeping DMA default
masks set-up on IORT based (ie ARM) arch configurations.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: Robin Murphy <robin.murphy@xxxxxxx>
Cc: Tomasz Nowicki <tn@xxxxxxxxxxxx>
Cc: Joerg Roedel <joro@xxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
Cc: Sricharan R <sricharan@xxxxxxxxxxxxxx>
---
Joerg,

pending Rafael's ACK on it, given the 4.10 release timing and that the
series is queued via the IOMMU tree please consider applying this patch to
your arm/smmu branch for 4.10, it is not fixing a bug but it is modifying
the x86/ia64 code path; I prefer preventing any issue related to default
dma masks on x86/ia64 so I hope it can get merged along with the rest of
the ACPI IORT SMMU series.

Thanks a lot and apologies,
Lorenzo

 drivers/acpi/arm64/iort.c | 22 ++++++++++++++++++++++
 drivers/acpi/scan.c       | 14 +-------------
 include/linux/acpi_iort.h |  2 ++
 3 files changed, 25 insertions(+), 13 deletions(-)

diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index 47bace8..e0d2e6e 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c
@@ -547,6 +547,28 @@ static const struct iommu_ops *iort_iommu_xlate(struct device *dev,
 }
 
 /**
+ * iort_set_dma_mask - Set-up dma mask for a device.
+ *
+ * @dev: device to configure
+ */
+void iort_set_dma_mask(struct device *dev)
+{
+	/*
+	 * Set default coherent_dma_mask to 32 bit.  Drivers are expected to
+	 * setup the correct supported mask.
+	 */
+	if (!dev->coherent_dma_mask)
+		dev->coherent_dma_mask = DMA_BIT_MASK(32);
+
+	/*
+	 * Set it to coherent_dma_mask by default if the architecture
+	 * code has not set it.
+	 */
+	if (!dev->dma_mask)
+		dev->dma_mask = &dev->coherent_dma_mask;
+}
+
+/**
  * iort_iommu_configure - Set-up IOMMU configuration for a device.
  *
  * @dev: device to configure
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 80698d3..93b00cf 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1380,19 +1380,7 @@ void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr)
 {
 	const struct iommu_ops *iommu;
 
-	/*
-	 * Set default coherent_dma_mask to 32 bit.  Drivers are expected to
-	 * setup the correct supported mask.
-	 */
-	if (!dev->coherent_dma_mask)
-		dev->coherent_dma_mask = DMA_BIT_MASK(32);
-
-	/*
-	 * Set it to coherent_dma_mask by default if the architecture
-	 * code has not set it.
-	 */
-	if (!dev->dma_mask)
-		dev->dma_mask = &dev->coherent_dma_mask;
+	iort_set_dma_mask(dev);
 
 	iommu = iort_iommu_configure(dev);
 
diff --git a/include/linux/acpi_iort.h b/include/linux/acpi_iort.h
index dcb2b60..77e0809 100644
--- a/include/linux/acpi_iort.h
+++ b/include/linux/acpi_iort.h
@@ -35,6 +35,7 @@ bool iort_node_match(u8 type);
 u32 iort_msi_map_rid(struct device *dev, u32 req_id);
 struct irq_domain *iort_get_device_domain(struct device *dev, u32 req_id);
 /* IOMMU interface */
+void iort_set_dma_mask(struct device *dev);
 const struct iommu_ops *iort_iommu_configure(struct device *dev);
 #else
 static inline void acpi_iort_init(void) { }
@@ -45,6 +46,7 @@ static inline struct irq_domain *iort_get_device_domain(struct device *dev,
 							u32 req_id)
 { return NULL; }
 /* IOMMU interface */
+static inline void iort_set_dma_mask(struct device *dev) { }
 static inline
 const struct iommu_ops *iort_iommu_configure(struct device *dev)
 { return NULL; }
-- 
2.10.0