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

["Sricharan" <sricharan@codeaurora.org>]

Hi Robin,

>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()?

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