linux-kernel - Re: [RFC PATCH v3 05/13] drivers: iommu: make iommu

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Message-ID: <1499f802-5f98-b0c0-d3aa-dabcac81e84e@arm.com>
Date:	Mon, 25 Jul 2016 16:09:55 +0100
From:	Robin Murphy <robin.murphy@....com>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	iommu@...ts.linux-foundation.org
Cc:	Will Deacon <will.deacon@....com>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	Joerg Roedel <joro@...tes.org>,
	Marc Zyngier <marc.zyngier@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Tomasz Nowicki <tn@...ihalf.com>, Jon Masters <jcm@...hat.com>,
	Sinan Kaya <okaya@...eaurora.org>, linux-acpi@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH v3 05/13] drivers: iommu: make iommu_fwspec OF
 agnostic

Hi Lorenzo,

On 20/07/16 12:23, Lorenzo Pieralisi wrote:
> The iommu_fwspec structure, used to hold per device iommu configuration
> data is not OF specific and therefore can be moved to a generic
> and OF independent compilation unit.
> 
> In particular, the iommu_fwspec handling hinges on the device_node
> pointer to identify the IOMMU device associated with the iommu_fwspec
> structure, that is easily converted to a more generic fwnode_handle
> pointer that can cater for OF and non-OF (ie ACPI) systems.
> 
> Create the files and related Kconfig entry to decouple iommu_fwspec
> structure from the OF iommu kernel layer.
> 
> Given that the current iommu_fwspec implementation relies on
> the arch specific struct device.archdata.iommu field in its
> implementation, by making the code standalone and independent
> of the OF layer this patch makes sure that the iommu_fwspec
> kernel code can be selected only on arches implementing the
> struct device.archdata.iommu field by adding an explicit
> arch dependency in its config entry.
> 
> Current drivers using the iommu_fwspec for streamid translation
> are converted to the new iommu_fwspec API by simply converting
> the device_node to its fwnode_handle pointer.
> 
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Hanjun Guo <hanjun.guo@...aro.org>
> Cc: Robin Murphy <robin.murphy@....com>
> Cc: Joerg Roedel <joro@...tes.org>
> ---
>  drivers/iommu/Kconfig        |   4 ++
>  drivers/iommu/Makefile       |   1 +
>  drivers/iommu/arm-smmu-v3.c  |  13 +++--
>  drivers/iommu/iommu-fwspec.c | 114 +++++++++++++++++++++++++++++++++++++++++++
>  drivers/iommu/of_iommu.c     |  52 --------------------
>  include/linux/iommu-fwspec.h |  60 +++++++++++++++++++++++
>  include/linux/of_iommu.h     |  24 +++------
>  7 files changed, 196 insertions(+), 72 deletions(-)
>  create mode 100644 drivers/iommu/iommu-fwspec.c
>  create mode 100644 include/linux/iommu-fwspec.h
> 
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index d1c66af..2b26bfb 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -67,6 +67,10 @@ config OF_IOMMU
>         def_bool y
>         depends on OF && IOMMU_API
>  
> +config IOMMU_FWSPEC
> +       def_bool y
> +       depends on ARM64 && IOMMU_API

I think that could be at least (ARM || ARM64).

> +
>  # IOMMU-agnostic DMA-mapping layer
>  config IOMMU_DMA
>  	bool

[...]

> diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
> index 308791f..2362232 100644
> --- a/include/linux/of_iommu.h
> +++ b/include/linux/of_iommu.h
> @@ -15,13 +15,8 @@ extern void of_iommu_init(void);
>  extern const struct iommu_ops *of_iommu_configure(struct device *dev,
>  					struct device_node *master_np);
>  
> -struct iommu_fwspec {
> -	const struct iommu_ops	*iommu_ops;
> -	struct device_node	*iommu_np;
> -	void			*iommu_priv;
> -	unsigned int		num_ids;
> -	u32			ids[];
> -};
> +void of_iommu_set_ops(struct device_node *np, const struct iommu_ops *ops);
> +const struct iommu_ops *of_iommu_get_ops(struct device_node *np);

Is there some reason we need to retain the existing definitions of
these? I was assuming we'd be able to move the entire implementation
over to the fwspec code and leave behind nothing more than trivial
wrappers, e.g.:

#define of_iommu_get_ops(np) iommu_fwspec_get_ops(&(np)->fwnode_handle)

Robin.

>  #else
>  
> @@ -39,17 +34,14 @@ static inline const struct iommu_ops *of_iommu_configure(struct device *dev,
>  	return NULL;
>  }
>  
> -struct iommu_fwspec;
> -
> -#endif	/* CONFIG_OF_IOMMU */
> +static inline void of_iommu_set_ops(struct device_node *np,
> +				    const struct iommu_ops *ops)
> +{ }
>  
> -int iommu_fwspec_init(struct device *dev, struct device_node *iommu_np);
> -void iommu_fwspec_free(struct device *dev);
> -int iommu_fwspec_add_ids(struct device *dev, u32 *ids, int num_ids);
> -struct iommu_fwspec *dev_iommu_fwspec(struct device *dev);
> +static inline const struct iommu_ops *
> +of_iommu_get_ops(struct device_node *np) { return NULL; }
>  
> -void of_iommu_set_ops(struct device_node *np, const struct iommu_ops *ops);
> -const struct iommu_ops *of_iommu_get_ops(struct device_node *np);
> +#endif	/* CONFIG_OF_IOMMU */
>  
>  extern struct of_device_id __iommu_of_table;
>  
>