linux-kernel - Re: [PATCH v4 1/6] of: iommu: add ptr to OF node arg to of_iommu

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Message-ID: <4711364.TTK5TCBdiy@avalon>
Date:	Sun, 25 Jan 2015 15:32:42 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Murali Karicheri <m-karicheri2@...com>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	devicetree@...r.kernel.org, iommu@...ts.linux-foundation.org,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will.deacon@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Grant Likely <grant.likely@...aro.org>
Subject: Re: [PATCH v4 1/6] of: iommu: add ptr to OF node arg to of_iommu_configure()

Hi Murali,

Thank you for the patch.

On Friday 23 January 2015 17:32:34 Murali Karicheri wrote:
> Function of_iommu_configure() is called from of_dma_configure() to
> setup iommu ops using DT property. This API is currently used for
> platform devices for which DMA configuration (including iommu ops)
> may come from device's parent. To extend this functionality for PCI
> devices, this API need to take a parent node ptr as an argument
> instead of assuming device's parent. This is needed since for PCI, the
> dma configuration may be defined in the DT node of the root bus bridge's
> parent device. Currently only dma-range is used for PCI and iommu is not
> supported. So return error if the device is PCI.
> 
> Cc: Joerg Roedel <joro@...tes.org>
> Cc: Grant Likely <grant.likely@...aro.org>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Russell King <linux@....linux.org.uk>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
> 
> Signed-off-by: Murali Karicheri <m-karicheri2@...com>
> ---
>  drivers/iommu/of_iommu.c |   10 ++++++++--
>  drivers/of/platform.c    |    2 +-
>  include/linux/of_iommu.h |    6 ++++--
>  3 files changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
> index af1dc6a..439235b 100644
> --- a/drivers/iommu/of_iommu.c
> +++ b/drivers/iommu/of_iommu.c
> @@ -133,19 +133,25 @@ struct iommu_ops *of_iommu_get_ops(struct device_node
> *np) return ops;
>  }
> 
> -struct iommu_ops *of_iommu_configure(struct device *dev)
> +struct iommu_ops *of_iommu_configure(struct device *dev,
> +				     struct device_node *iommu_np)
>  {
>  	struct of_phandle_args iommu_spec;
>  	struct device_node *np;
>  	struct iommu_ops *ops = NULL;
>  	int idx = 0;
> 
> +	if (dev_is_pci(dev)) {
> +		dev_err(dev, "iommu is currently not supported for PCI\n");
> +		return NULL;
> +	}
> +
>  	/*
>  	 * We don't currently walk up the tree looking for a parent IOMMU.
>  	 * See the `Notes:' section of
>  	 * Documentation/devicetree/bindings/iommu/iommu.txt
>  	 */

Wouldn't it be better to fix this rather than passing the device node pointer 
to the function ? The solution would be more generic.

> -	while (!of_parse_phandle_with_args(dev->of_node, "iommus",
> +	while (!of_parse_phandle_with_args(iommu_np, "iommus",
>  					   "#iommu-cells", idx,
>  					   &iommu_spec)) {
>  		np = iommu_spec.np;
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index a54ec10..7675b79 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -196,7 +196,7 @@ static void of_dma_configure(struct device *dev)
>  	dev_dbg(dev, "device is%sdma coherent\n",
>  		coherent ? " " : " not ");
> 
> -	iommu = of_iommu_configure(dev);
> +	iommu = of_iommu_configure(dev, dev->of_node);
>  	dev_dbg(dev, "device is%sbehind an iommu\n",
>  		iommu ? " " : " not ");
> 
> diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
> index 16c7554..a97e5bd 100644
> --- a/include/linux/of_iommu.h
> +++ b/include/linux/of_iommu.h
> @@ -12,7 +12,8 @@ extern int of_get_dma_window(struct device_node *dn, const
> char *prefix, size_t *size);
> 
>  extern void of_iommu_init(void);
> -extern struct iommu_ops *of_iommu_configure(struct device *dev);
> +extern struct iommu_ops *of_iommu_configure(struct device *dev,
> +					struct device_node *iommu_np);
> 
>  #else
> 
> @@ -24,7 +25,8 @@ static inline int of_get_dma_window(struct device_node
> *dn, const char *prefix, }
> 
>  static inline void of_iommu_init(void) { }
> -static inline struct iommu_ops *of_iommu_configure(struct device *dev)
> +static inline struct iommu_ops *of_iommu_configure(struct device *dev,
> +					 struct device_node *iommu_np)
>  {
>  	return NULL;
>  }

-- 
Regards,

Laurent Pinchart

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