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

[Robin Murphy <robin.murphy@arm.com>]

+Lorenzo

On 04/10/16 18:03, 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 <sricharan@codeaurora.org>
> ---
>  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()?

Robin.

> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index 66533e1..2766dbe 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -656,6 +656,9 @@ 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
>   */
>