[PATCH RFC 02/17] of: Do not return struct iommu_ops from of_iommu_configure()

[Jerry Snitselaar]

On Fri, Nov 03, 2023 at 01:44:47PM -0300, Jason Gunthorpe wrote:
> Nothing needs this pointer. Return a normal error code with the usual
> IOMMU semantic that ENODEV means 'there is no IOMMU driver'.
> 
> Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
> ---
>  drivers/iommu/of_iommu.c | 29 ++++++++++++++++++-----------
>  drivers/of/device.c      | 22 +++++++++++++++-------
>  include/linux/of_iommu.h | 13 ++++++-------
>  3 files changed, 39 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
> index 157b286e36bf3a..e2fa29c16dd758 100644
> --- a/drivers/iommu/of_iommu.c
> +++ b/drivers/iommu/of_iommu.c
> @@ -107,20 +107,26 @@ static int of_iommu_configure_device(struct device_node *master_np,
>  		      of_iommu_configure_dev(master_np, dev);
>  }
>  
> -const struct iommu_ops *of_iommu_configure(struct device *dev,
> -					   struct device_node *master_np,
> -					   const u32 *id)
> +/*
> + * Returns:
> + *  0 on success, an iommu was configured
> + *  -ENODEV if the device does not have any IOMMU
> + *  -EPROBEDEFER if probing should be tried again
> + *  -errno fatal errors

It looks to me like it will only return 0, -ENODEV, or -EPROBEDEFER
with other -errno getting boiled down to -ENODEV.

> + */
> +int of_iommu_configure(struct device *dev, struct device_node *master_np,
> +		       const u32 *id)
>  {
>  	const struct iommu_ops *ops = NULL;
>  	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
>  	int err = NO_IOMMU;
>  
>  	if (!master_np)
> -		return NULL;
> +		return -ENODEV;
>  
>  	if (fwspec) {
>  		if (fwspec->ops)
> -			return fwspec->ops;
> +			return 0;
>  
>  		/* In the deferred case, start again from scratch */
>  		iommu_fwspec_free(dev);
> @@ -163,14 +169,15 @@ const struct iommu_ops *of_iommu_configure(struct device *dev,
>  		err = iommu_probe_device(dev);
>  
>  	/* Ignore all other errors apart from EPROBE_DEFER */
> -	if (err == -EPROBE_DEFER) {
> -		ops = ERR_PTR(err);
> -	} else if (err < 0) {
> +	if (err < 0) {
> +		if (err == -EPROBE_DEFER)
> +			return err;
>  		dev_dbg(dev, "Adding to IOMMU failed: %d\n", err);

minor thing, but should this use %pe and ERR_PTR(err) like is done
in of_dma_configure_id?

> -		ops = NULL;
> +		return -ENODEV;
>  	}
> -
> -	return ops;
> +	if (!ops)
> +		return -ENODEV;
> +	return 0;
>  }
>  
>  static enum iommu_resv_type __maybe_unused
> diff --git a/drivers/of/device.c b/drivers/of/device.c
> index 65c71be71a8d45..873d933e8e6d1d 100644
> --- a/drivers/of/device.c
> +++ b/drivers/of/device.c
> @@ -93,12 +93,12 @@ of_dma_set_restricted_buffer(struct device *dev, struct device_node *np)
>  int of_dma_configure_id(struct device *dev, struct device_node *np,
>  			bool force_dma, const u32 *id)
>  {
> -	const struct iommu_ops *iommu;
>  	const struct bus_dma_region *map = NULL;
>  	struct device_node *bus_np;
>  	u64 dma_start = 0;
>  	u64 mask, end, size = 0;
>  	bool coherent;
> +	int iommu_ret;
>  	int ret;
>  
>  	if (np == dev->of_node)
> @@ -181,21 +181,29 @@ int of_dma_configure_id(struct device *dev, struct device_node *np,
>  	dev_dbg(dev, "device is%sdma coherent\n",
>  		coherent ? " " : " not ");
>  
> -	iommu = of_iommu_configure(dev, np, id);
> -	if (PTR_ERR(iommu) == -EPROBE_DEFER) {
> +	iommu_ret = of_iommu_configure(dev, np, id);
> +	if (iommu_ret == -EPROBE_DEFER) {
>  		/* Don't touch range map if it wasn't set from a valid dma-ranges */
>  		if (!ret)
>  			dev->dma_range_map = NULL;
>  		kfree(map);
>  		return -EPROBE_DEFER;
> -	}
> +	} else if (iommu_ret == -ENODEV) {
> +		dev_dbg(dev, "device is not behind an iommu\n");
> +	} else if (iommu_ret) {
> +		dev_err(dev, "iommu configuration for device failed with %pe\n",
> +			ERR_PTR(iommu_ret));
>  
> -	dev_dbg(dev, "device is%sbehind an iommu\n",
> -		iommu ? " " : " not ");
> +		/*
> +		 * Historically this routine doesn't fail driver probing
> +		 * due to errors in of_iommu_configure()
> +		 */
> +	} else
> +		dev_dbg(dev, "device is behind an iommu\n");
>  
>  	arch_setup_dma_ops(dev, dma_start, size, coherent);
>  
> -	if (!iommu)
> +	if (iommu_ret)
>  		of_dma_set_restricted_buffer(dev, np);
>  
>  	return 0;
> diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
> index 9a5e6b410dd2fb..e61cbbe12dac6f 100644
> --- a/include/linux/of_iommu.h
> +++ b/include/linux/of_iommu.h
> @@ -8,20 +8,19 @@ struct iommu_ops;
>  
>  #ifdef CONFIG_OF_IOMMU
>  
> -extern const struct iommu_ops *of_iommu_configure(struct device *dev,
> -					struct device_node *master_np,
> -					const u32 *id);
> +extern int of_iommu_configure(struct device *dev, struct device_node *master_np,
> +			      const u32 *id);
>  
>  extern void of_iommu_get_resv_regions(struct device *dev,
>  				      struct list_head *list);
>  
>  #else
>  
> -static inline const struct iommu_ops *of_iommu_configure(struct device *dev,
> -					 struct device_node *master_np,
> -					 const u32 *id)
> +static inline int of_iommu_configure(struct device *dev,
> +				     struct device_node *master_np,
> +				     const u32 *id)
>  {
> -	return NULL;
> +	return -ENODEV;
>  }
>  
>  static inline void of_iommu_get_resv_regions(struct device *dev,
> -- 
> 2.42.0
>