Re: [PATCH v5 06/14] drivers: acpi: implement acpi_dma_configure

On Tue, Sep 13, 2016 at 03:41:06PM +0100, Robin Murphy wrote:

On 09/09/16 15:23, Lorenzo Pieralisi wrote:

quoted

On DT based systems, the of_dma_configure() API implements DMA
configuration for a given device. On ACPI systems an API equivalent to
of_dma_configure() is missing which implies that it is currently not
possible to set-up DMA operations for devices through the ACPI generic
kernel layer.

This patch fills the gap by introducing acpi_dma_configure/deconfigure()
calls that for now are just wrappers around arch_setup_dma_ops() and
arch_teardown_dma_ops() and also updates ACPI and PCI core code to use
the newly introduced acpi_dma_configure/acpi_dma_deconfigure functions.

The DMA range size passed to arch_setup_dma_ops() is sized according
to the device coherent_dma_mask (starting at address 0x0), mirroring the
DT probing path behaviour when a dma-ranges property is not provided
for the device being probed; this changes the current arch_setup_dma_ops()
call parameters in the ACPI probing case, but since arch_setup_dma_ops()
is a NOP on all architectures but ARM/ARM64 this patch does not change
the current kernel behaviour on them.

Signed-off-by: Lorenzo Pieralisi <redacted>
Acked-by: Bjorn Helgaas <bhelgaas@google.com> [pci]
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Tomasz Nowicki <redacted>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: "Rafael J. Wysocki" <redacted>
---
 drivers/acpi/glue.c     |  4 ++--
 drivers/acpi/scan.c     | 24 ++++++++++++++++++++++++
 drivers/pci/probe.c     |  3 +--
 include/acpi/acpi_bus.h |  2 ++
 include/linux/acpi.h    |  5 +++++
 5 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
index 5ea5dc2..f8d6564 100644
--- a/drivers/acpi/glue.c
+++ b/drivers/acpi/glue.c

@@ -227,8 +227,7 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev)
 
 	attr = acpi_get_dma_attr(acpi_dev);
 	if (attr != DEV_DMA_NOT_SUPPORTED)
-		arch_setup_dma_ops(dev, 0, 0, NULL,
-				   attr == DEV_DMA_COHERENT);
+		acpi_dma_configure(dev, attr);

Here's the call for non-PCI devices ;-)

quoted

 	acpi_physnode_link_name(physical_node_name, node_id);
 	retval = sysfs_create_link(&acpi_dev->dev.kobj, &dev->kobj,

@@ -251,6 +250,7 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev)
 	return 0;
 
  err:
+	acpi_dma_deconfigure(dev);
 	ACPI_COMPANION_SET(dev, NULL);
 	put_device(dev);
 	put_device(&acpi_dev->dev);

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index e878fc7..9614232 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c

@@ -1370,6 +1370,30 @@ enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev)
 		return DEV_DMA_NON_COHERENT;
 }
 
+/**
+ * acpi_dma_configure - Set-up DMA configuration for the device.
+ * @dev: The pointer to the device
+ * @attr: device dma attributes
+ */
+void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr)
+{
+	/*
+	 * Assume dma valid range starts at 0 and covers the whole
+	 * coherent_dma_mask.
+	 */
+	arch_setup_dma_ops(dev, 0, dev->coherent_dma_mask + 1, NULL,
+			   attr == DEV_DMA_COHERENT);

This looks a bit hairy - if we're setting up the DMA configuration at
this point can we really always rely on the device already having a
valid DMA mask? I think it would make sense to at least check, and apply
the standard default 32-bit mask  if not.

That's a good point, but we would be changing the x86/IA64 probing path
if we do what you suggest; so I think you are right and it should be a
safe change to make but I still need to make sure we do not break
anything in the process.

quoted

+}
+
+/**
+ * acpi_dma_deconfigure - Tear-down DMA configuration for the device.
+ * @dev: The pointer to the device
+ */
+void acpi_dma_deconfigure(struct device *dev)
+{
+	arch_teardown_dma_ops(dev);
+}

As touched upon in the dwc-usb3 thread, is it worth exporting these for
the benefit of modular bus/glue code, to match of_dma_configure()?

I think yes, I will do.

quoted

 static void acpi_init_coherency(struct acpi_device *adev)
 {
 	unsigned long long cca = 0;

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 93f280d..e96d482 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c

@@ -1734,8 +1734,7 @@ static void pci_dma_configure(struct pci_dev *dev)
 		if (attr == DEV_DMA_NOT_SUPPORTED)
 			dev_warn(&dev->dev, "DMA not supported.\n");
 		else
-			arch_setup_dma_ops(&dev->dev, 0, 0, NULL,
-					   attr == DEV_DMA_COHERENT);
+			acpi_dma_configure(&dev->dev, attr);
 	}

What about non-PCI stuff? I see there's at least an
acpi_create_platform_device() which I'd also kind of expect to see as a
caller (which indeed might also tie in with the aforementioned default
mask initialisation).

See above (acpi_bind_one()).

Thanks for having a look,
Lorenzo

Robin.

quoted

 
 	pci_put_host_bridge_device(bridge);

diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index c1a524d..4242c31 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h

@@ -573,6 +573,8 @@ struct acpi_pci_root {
 
 bool acpi_dma_supported(struct acpi_device *adev);
 enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev);
+void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr);
+void acpi_dma_deconfigure(struct device *dev);
 
 struct acpi_device *acpi_find_child_device(struct acpi_device *parent,
 					   u64 address, bool check_children);

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index c5eaf2f..05d4e48 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h

@@ -729,6 +729,11 @@ static inline enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev)
 	return DEV_DMA_NOT_SUPPORTED;
 }
 
+static inline void acpi_dma_configure(struct device *dev,
+				      enum dev_dma_attr attr) { }
+
+static inline void acpi_dma_deconfigure(struct device *dev) { }
+
 #define ACPI_PTR(_ptr)	(NULL)
 
 static inline void acpi_device_set_enumerated(struct acpi_device *adev)

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