[RFC PATCH 4/7] iommu: provide helper function to configure an IOMMU for an of master

[Varun Sethi]

Hi Will,
I am not clear on the functionality we want to achieve with this new API. Is this a way to link devices to a particular IOMMU? Would this be used to filter out add_device invocations i.e. iommu group creations just  for the devices attached to a particular IOMMU?

What is the purpose of the data pointer, that is being passed to this API? Also, how would this be relevant to PCIe devices (also other hot plug devices).

Regards
Varun

> -----Original Message-----
> From: Will Deacon [mailto:will.deacon at arm.com]
> Sent: Friday, August 29, 2014 9:24 PM
> To: linux-arm-kernel at lists.infradead.org; iommu at lists.linux-foundation.org
> Cc: arnd at arndb.de; dwmw2 at infradead.org; jroedel at suse.de;
> hdoyu at nvidia.com; Sethi Varun-B16395; thierry.reding at gmail.com;
> laurent.pinchart at ideasonboard.com; Will Deacon
> Subject: [RFC PATCH 4/7] iommu: provide helper function to configure an
> IOMMU for an of master
> 
> The generic IOMMU device-tree bindings can be used to add arbitrary OF
> masters to an IOMMU with a compliant binding.
> 
> This patch introduces of_iommu_configure, which does exactly that.
> 
> Signed-off-by: Will Deacon <will.deacon at arm.com>
> ---
>  drivers/iommu/Kconfig    |  2 +-
>  drivers/iommu/of_iommu.c | 36
> ++++++++++++++++++++++++++++++++++++
>  include/linux/of_iommu.h |  6 ++++++
>  3 files changed, 43 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig index
> dd5112265cc9..6d13f962f156 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -15,7 +15,7 @@ if IOMMU_SUPPORT
> 
>  config OF_IOMMU
>         def_bool y
> -       depends on OF
> +       depends on OF && IOMMU_API
> 
>  config FSL_PAMU
>  	bool "Freescale IOMMU support"
> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c index
> f9209666157c..a7d3b3a13b83 100644
> --- a/drivers/iommu/of_iommu.c
> +++ b/drivers/iommu/of_iommu.c
> @@ -19,6 +19,7 @@
> 
>  #include <linux/export.h>
>  #include <linux/limits.h>
> +#include <linux/iommu.h>
>  #include <linux/of.h>
>  #include <linux/of_iommu.h>
> 
> @@ -90,6 +91,41 @@ int of_get_dma_window(struct device_node *dn, const
> char *prefix, int index,  }  EXPORT_SYMBOL_GPL(of_get_dma_window);
> 
> +int of_iommu_configure(struct device *dev) {
> +	struct of_phandle_args iommu_spec;
> +	struct bus_type *bus = dev->bus;
> +	const struct iommu_ops *ops = bus->iommu_ops;
> +	int ret = -EINVAL, idx = 0;
> +
> +	if (!iommu_present(bus))
> +		return -ENODEV;
> +
> +	/*
> +	 * We don't currently walk up the tree looking for a parent IOMMU.
> +	 * See the `Notes:' section of
> +	 * Documentation/devicetree/bindings/iommu/iommu.txt
> +	 */
> +	while (!of_parse_phandle_with_args(dev->of_node, "iommus",
> +					   "#iommu-cells", idx,
> +					   &iommu_spec)) {
> +		void *data = of_iommu_get_data(iommu_spec.np);
> +
> +		of_node_put(iommu_spec.np);
> +		if (!ops->add_device_master_ids)
> +			return -ENODEV;
> +
> +		ret = ops->add_device_master_ids(dev,
> iommu_spec.args_count,
> +						 iommu_spec.args, data);
> +		if (ret)
> +			break;
> +
> +		idx++;
> +	}
> +
> +	return ret;
> +}
> +
>  void __init of_iommu_init(void)
>  {
>  	struct device_node *np;
> diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h index
> 29f2f3f88d6a..85c6d1152624 100644
> --- a/include/linux/of_iommu.h
> +++ b/include/linux/of_iommu.h
> @@ -1,6 +1,7 @@
>  #ifndef __OF_IOMMU_H
>  #define __OF_IOMMU_H
> 
> +#include <linux/device.h>
>  #include <linux/of.h>
> 
>  #ifdef CONFIG_OF_IOMMU
> @@ -10,6 +11,7 @@ extern int of_get_dma_window(struct device_node *dn,
> const char *prefix,
>  			     size_t *size);
> 
>  extern void of_iommu_init(void);
> +extern int of_iommu_configure(struct device *dev);
> 
>  #else
> 
> @@ -21,6 +23,10 @@ static inline int of_get_dma_window(struct device_node
> *dn, const char *prefix,  }
> 
>  static inline void of_iommu_init(void) { }
> +static inline int of_iommu_configure(struct device *dev) {
> +	return -ENODEV;
> +}
> 
>  #endif	/* CONFIG_OF_IOMMU */
> 
> --
> 2.1.0