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

Robin Murphy
2016-10-26T14:07:58Z

+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
> */
>