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

From: [email-masked] (Lorenzo Pieralisi)
Date: Thu, 19 Jan 2017 19:02:50 +0000

On Thu, Jan 19, 2017 at 05:49:58PM +0000, Robin Murphy wrote:
> On 19/01/17 15:05, Sricharan R wrote:
> > 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 <[email-masked]>
> > ---
> >  * 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).

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

Thanks,
Lorenzo

> 	}
> 
> 	if (dma_dev && dma_dev->of_node) {
> 		of_dma_configure(dev, dma_dev->of_node);
> 	} else if (dma_dev && has_acpi_companion(dma_dev)) {
> 		struct acpi_device *adev = to_acpi_device_node(dma_dev->fwnode);
> 		enum dev_dma_attr attr = acpi_get_dma_attr(adev);
> 
> 		if (attr == DEV_DMA_NOT_SUPPORTED)
> 			dev_warn(dev, "DMA not supported.\n");
> 		else
> 			arch_setup_dma_ops(dev, 0, 0, NULL,
> 					   attr == DEV_DMA_COHERENT);
> 	}
> 
> 	if (bridge)
> 		pci_put_host_bridge_device(bridge);
> 
> 	return 0;
> }
> ---8<---
> 
> I have a feeling I was having a go at tidying up the "PCI hacks" from v4
> myself, but other things ended up taking precedence.
> 
> Robin.
> 
> > +
> > +	return 0;
> > +}
> > +
> > +void dma_deconfigure(struct device *dev)
> > +{
> > +	of_dma_deconfigure(dev);
> > +}
> > diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> > index 57418f7..cf35030 100644
> > --- a/drivers/of/platform.c
> > +++ b/drivers/of/platform.c
> > @@ -22,6 +22,7 @@
> >  #include <linux/slab.h>
> >  #include <linux/of_address.h>
> >  #include <linux/of_device.h>
> > +#include <linux/of_iommu.h>
> >  #include <linux/of_irq.h>
> >  #include <linux/of_platform.h>
> >  #include <linux/platform_device.h>
> > @@ -186,11 +187,9 @@ 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;
> >  	}
> > @@ -248,7 +247,6 @@ 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);
> > @@ -542,7 +540,6 @@ 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 e164b5c..634d34e 100644
> > --- a/drivers/pci/probe.c
> > +++ b/drivers/pci/probe.c
> > @@ -1873,10 +1873,7 @@ 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);
> >  
> > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> > index abf685ed..b56320a 100644
> > --- a/include/linux/dma-mapping.h
> > +++ b/include/linux/dma-mapping.h
> > @@ -718,6 +718,9 @@ void *dma_mark_declared_memory_occupied(struct device *dev,
> >  }
> >  #endif /* CONFIG_HAVE_GENERIC_DMA_COHERENT */
> >  
> > +int dma_configure(struct device *dev);
> > +void dma_deconfigure(struct device *dev);
> > +
> >  /*
> >   * Managed DMA API
> >   */
> > 
>