[PATCH V3 4/8] drivers: platform: Configure dma operations at probe time

Hi Robin,

On 04/10/16 18:03, Sricharan R wrote:

quoted

Configuring DMA ops at probe time will allow deferring device probe when
the IOMMU isn't available yet. The dma_configure for the device is now called
from the generic device_attach callback just before the bus/driver probe
is called. This way, configuring the dma ops for the device would be called
at the same place for all bus_types, hence the deferred probing mechanism
should work for all buses as well.

pci_bus_add_devices    (platform/amba)(_device_create/driver_register)
       |                         |
pci_bus_add_device     (device_add/driver_register)
       |                         |
device_attach           device_initial_probe
       |                         |
__device_attach_driver    __device_attach_driver
       |
driver_probe_device
       |
really_probe
       |
dma_configure

 Similarly on the device/driver_unregister path __device_release_driver is
 called which inturn calls dma_deconfigure.

Signed-off-by: Sricharan R <redacted>
---
 drivers/base/dd.c           | 10 ++++++++++
 drivers/base/dma-mapping.c  | 11 +++++++++++
 drivers/of/platform.c       |  4 ----
 drivers/pci/probe.c         |  5 +----
 include/linux/dma-mapping.h |  3 +++
 5 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 16688f5..cfebd48 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c

@@ -19,6 +19,7 @@

 #include <linux/device.h>
 #include <linux/delay.h>
+#include <linux/dma-mapping.h>
 #include <linux/module.h>
 #include <linux/kthread.h>
 #include <linux/wait.h>

@@ -353,6 +354,10 @@ static int really_probe(struct device *dev, struct device_driver *drv)
 	if (ret)
 		goto pinctrl_bind_failed;

+	ret = dma_configure(dev);
+	if (ret)
+		goto dma_failed;
+
 	if (driver_sysfs_add(dev)) {
 		printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
 			__func__, dev_name(dev));

@@ -395,6 +400,8 @@ static int really_probe(struct device *dev, struct device_driver *drv)
 	goto done;

 probe_failed:
+	dma_deconfigure(dev);
+dma_failed:
 	if (dev->bus)
 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 					     BUS_NOTIFY_DRIVER_NOT_BOUND, dev);

@@ -780,6 +787,9 @@ static void __device_release_driver(struct device *dev)
 			dev->bus->remove(dev);
 		else if (drv->remove)
 			drv->remove(dev);
+
+		dma_deconfigure(dev);
+
 		devres_release_all(dev);
 		dev->driver = NULL;
 		dev_set_drvdata(dev, NULL);

diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
index d799662..54e87f5 100644
--- a/drivers/base/dma-mapping.c
+++ b/drivers/base/dma-mapping.c

@@ -10,6 +10,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/export.h>
 #include <linux/gfp.h>
+#include <linux/of_device.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>

@@ -166,6 +167,16 @@ void dmam_free_noncoherent(struct device *dev, size_t size, void *vaddr,
 }
 EXPORT_SYMBOL(dmam_free_noncoherent);

+int dma_configure(struct device *dev)
+{
+	return of_dma_configure(dev, dev->of_node);
+}
+
+void dma_deconfigure(struct device *dev)
+{
+	of_dma_deconfigure(dev);
+}
+
 #ifdef CONFIG_HAVE_GENERIC_DMA_COHERENT

 static void dmam_coherent_decl_release(struct device *dev, void *res)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index 9cb7090..adbd77c 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c

@@ -181,11 +181,9 @@ static struct platform_device *of_platform_device_create_pdata(

 	dev->dev.bus = &platform_bus_type;
 	dev->dev.platform_data = platform_data;
-	of_dma_configure(&dev->dev, dev->dev.of_node);
 	of_msi_configure(&dev->dev, dev->dev.of_node);

 	if (of_device_add(dev) != 0) {
-		of_dma_deconfigure(&dev->dev);
 		platform_device_put(dev);
 		goto err_clear_flag;
 	}

@@ -242,7 +240,6 @@ static struct amba_device *of_amba_device_create(struct device_node *node,
 		dev_set_name(&dev->dev, "%s", bus_id);
 	else
 		of_device_make_bus_id(&dev->dev);
-	of_dma_configure(&dev->dev, dev->dev.of_node);

 	/* Allow the HW Peripheral ID to be overridden */
 	prop = of_get_property(node, "arm,primecell-periphid", NULL);

@@ -536,7 +533,6 @@ static int of_platform_device_destroy(struct device *dev, void *data)
 		amba_device_unregister(to_amba_device(dev));
 #endif

-	of_dma_deconfigure(dev);
 	of_node_clear_flag(dev->of_node, OF_POPULATED);
 	of_node_clear_flag(dev->of_node, OF_POPULATED_BUS);
 	return 0;

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 93f280d..85c9553 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c

@@ -1724,10 +1724,7 @@ static void pci_dma_configure(struct pci_dev *dev)
 {
 	struct device *bridge = pci_get_host_bridge_device(dev);

-	if (IS_ENABLED(CONFIG_OF) &&
-		bridge->parent && bridge->parent->of_node) {
-			of_dma_configure(&dev->dev, bridge->parent->of_node);
-	} else if (has_acpi_companion(bridge)) {
+	if (has_acpi_companion(bridge)) {
 		struct acpi_device *adev = to_acpi_device_node(bridge->fwnode);
 		enum dev_dma_attr attr = acpi_get_dma_attr(adev);

It seems a bit awkward leaving pci_dma_configure here, doing DMA
configuration at device add, after we've allegedly moved DMA
configuration to driver probe. Lorenzo, do you foresee any issues if
this probe-time of_dma_configure() path were to also multiplex
acpi_dma_configure() in future, such that everything would be back in
the same place eventually?

Conversely, is there actually any issue with leaving pci_dma_configure()
unchanged, and simply moving the call from pci_device_add() into
dma_configure()?

Ya i removed only the CONFIG_OF part out of this, and was hoping that
the acpi configure can also be called from the dma_configure during
probe later. I did not have an ACPI based platform though.
 As you said, if that looks right to the ACPI world, it can be
moved out from here. I can try mergin series (after fixing the vfio errors
 part) with the ACPI IO port and see how it behaves.

Regards,
 Sricharan