[PATCH V5 05/12] drivers: platform: Configure dma operations at probe time

Hi,

quoted

quoted

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>
---
 * Removed the dma configuration for the pci devices in case of DT
   from pci_dma_configure which was hanging outside separately and
   doing it in dma_configure function itself.

 drivers/base/dd.c           |  9 +++++++++
 drivers/base/dma-mapping.c  | 32 ++++++++++++++++++++++++++++++++
 drivers/of/platform.c       |  5 +----
 drivers/pci/probe.c         |  5 +----
 include/linux/dma-mapping.h |  3 +++
 5 files changed, 46 insertions(+), 8 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index a1fbf55..4882f06 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>

@@ -356,6 +357,10 @@ 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));

@@ -417,6 +422,8 @@ 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);

@@ -826,6 +833,8 @@ static void __device_release_driver(struct device *dev, struct device *parent)
 			drv->remove(dev);

 		device_links_driver_cleanup(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 efd71cf..dfe6fd7 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>

@@ -341,3 +342,34 @@ void dma_common_free_remap(void *cpu_addr, size_t size, unsigned long vm_flags)
 	vunmap(cpu_addr);
 }
 #endif
+
+/*
+ * Common configuration to enable DMA API use for a device
+ */
+#include <linux/pci.h>
+
+int dma_configure(struct device *dev)
+{
+	struct device *_dev = dev;
+	int is_pci = dev_is_pci(dev);
+
+	if (is_pci) {
+		_dev = pci_get_host_bridge_device(to_pci_dev(dev));
+		if (IS_ENABLED(CONFIG_OF) && _dev->parent &&
+		    _dev->parent->of_node)
+			_dev = _dev->parent;
+	}
+
+	if (_dev->of_node)
+		of_dma_configure(dev, _dev->of_node);
+
+	if (is_pci)
+		pci_put_host_bridge_device(_dev);

There's a fun bug here - at this point _dev is the *parent* of the
bridge device, so we put the refcount on the wrong device (the platform
device representing the host controller, rather than the PCI device
representing its insides), which frees the guy we're in the middle of
probing, and things rapidly go wrong afterwards:

[    1.461026] bus: 'platform': driver_probe_device: matched device
40000000.pcie-controller with driver pci-host-generic
[    1.471640] bus: 'platform': really_probe: probing driver
pci-host-generic with device 40000000.pcie-controller
[    1.481678] OF: PCI: host bridge /pcie-controller at 40000000 ranges:

...

[    2.158259] bus: 'pci': driver_probe_device: matched device
0000:02:10.0 with driver pcieport
[    2.166716] bus: 'pci': really_probe: probing driver pcieport with
device 0000:02:10.0
[    2.174590] pci 0000:02:10.0: Driver pcieport requests probe deferral
[    2.180978] pci 0000:02:10.0: Added to deferred list
[    2.185915] bus: 'pci': driver_probe_device: matched device
0000:02:1f.0 with driver pcieport
[    2.194366] bus: 'pci': really_probe: probing driver pcieport with
device 0000:02:1f.0
[    2.202237] pci 0000:02:1f.0: Driver pcieport requests probe deferral
[    2.208625] pci 0000:02:1f.0: Added to deferred list
[    2.213582] driver: 'pci-host-generic': driver_bound: bound to device
'???v????.pcie-controller'
[    2.222293] bus: 'platform': really_probe: bound device
???v????.pcie-controller to driver pci-host-generic
[    2.232041] Unable to handle kernel NULL pointer dereference at
virtual address 00000000

I recall debugging this same issue before, and I seem to have a local
version of this commit dated about 6 weeks ago where dma_configure()
looks like this:

--->8---
int dma_configure(struct device *dev)
{
	struct device *bridge = NULL, *dma_dev = dev;

	if (dev_is_pci(dev)) {
		bridge = pci_get_host_bridge_device(to_pci_dev(dev));
		dma_dev = bridge->parent;

This would break ACPI, dma_dev would be NULL here, so from
this standpoint (ACPI) the current patch is correct (but those [dev,_dev]
should be renamed, they are extremely misleading so naming as
in this hunk, which fixes DT too, is very welcome).

Ya, I was also thinking about the _ variable names in first place.
So i will use the names that Robin showed in his hunk and fix the 
DT case that he pointed out.

Regards,
 Sricharan

On ACPI the DMA attributes are checked on the bridge's companion
(ie its associated acpi_device).