Subject: Re: [PATCH 6/6] iommu/arm-smmu: Make use of phandle iterators in
 device-tree parsing
To: Joerg Roedel <joro@8bytes.org>, Rob Herring <robh+dt@kernel.org>,
        grant.likely@linaro.org
References: <1458669509-7178-1-git-send-email-joro@8bytes.org>
 <1458669509-7178-7-git-send-email-joro@8bytes.org>
Cc: devicetree@vger.kernel.org, jroedel@suse.de,
        Will Deacon <will.deacon@arm.com>, linux-kernel@vger.kernel.org,
        iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org
From: Robin Murphy <robin.murphy@arm.com>
Message-ID: <56F194BC.3020709@arm.com>
Date: Tue, 22 Mar 2016 18:53:48 +0000
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Hi Joerg,

On 22/03/16 17:58, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@suse.de>
>
> Remove the usage of of_parse_phandle_with_args() and replace
> it by the phandle-iterator implementation so that we can
> parse out all of the potentially present 128 stream-ids.

In a stream-matching implementation, a device may quite legitimately own 
anything up to _all_ of the stream IDs (32768, or 65536 if we ever 
implement support for the SMMUv2 EXID extension), so this is only a 
genuine limit for stream indexing (and if anyone ever actually made one 
of those, I don't think they're running mainline on it).

Alternatively, how straightforward is it to change the DT on your 
machine? I'll be getting a v2 of [1] out in a couple of weeks (after 
imminent holidays), which already gets rid of MAX_MASTER_STREAMIDS 
altogether, and might also have grown proper SMR support by then.

Robin.

[1]:http://thread.gmane.org/gmane.linux.kernel.iommu/12454

> Signed-off-by: Joerg Roedel <jroedel@suse.de>
> ---
>   drivers/iommu/arm-smmu.c | 28 ++++++++++++++++++++++------
>   1 file changed, 22 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 59ee4b8..413bd64 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -48,7 +48,7 @@
>   #include "io-pgtable.h"
>
>   /* Maximum number of stream IDs assigned to a single device */
> -#define MAX_MASTER_STREAMIDS		MAX_PHANDLE_ARGS
> +#define MAX_MASTER_STREAMIDS		128
>
>   /* Maximum number of context banks per SMMU */
>   #define ARM_SMMU_MAX_CBS		128
> @@ -349,6 +349,12 @@ struct arm_smmu_domain {
>   	struct iommu_domain		domain;
>   };
>
> +struct arm_smmu_phandle_args {
> +	struct device_node *np;
> +	int args_count;
> +	uint32_t args[MAX_MASTER_STREAMIDS];
> +};
> +
>   static struct iommu_ops arm_smmu_ops;
>
>   static DEFINE_SPINLOCK(arm_smmu_devices_lock);
> @@ -458,7 +464,7 @@ static int insert_smmu_master(struct arm_smmu_device *smmu,
>
>   static int register_smmu_master(struct arm_smmu_device *smmu,
>   				struct device *dev,
> -				struct of_phandle_args *masterspec)
> +				struct arm_smmu_phandle_args *masterspec)
>   {
>   	int i;
>   	struct arm_smmu_master *master;
> @@ -1716,7 +1722,8 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev)
>   	struct arm_smmu_device *smmu;
>   	struct device *dev = &pdev->dev;
>   	struct rb_node *node;
> -	struct of_phandle_args masterspec;
> +	struct of_phandle_iterator it;
> +	struct arm_smmu_phandle_args masterspec;
>   	int num_irqs, i, err;
>
>   	smmu = devm_kzalloc(dev, sizeof(*smmu), GFP_KERNEL);
> @@ -1777,9 +1784,14 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev)
>
>   	i = 0;
>   	smmu->masters = RB_ROOT;
> -	while (!of_parse_phandle_with_args(dev->of_node, "mmu-masters",
> -					   "#stream-id-cells", i,
> -					   &masterspec)) {
> +
> +	of_for_each_phandle(&it, err, dev->of_node,
> +			    "mmu-masters", "#stream-id-cells", 0) {
> +		int count = of_phandle_iterator_args(&it, masterspec.args,
> +						     MAX_MASTER_STREAMIDS);
> +		masterspec.np		= of_node_get(it.node);
> +		masterspec.args_count	= count;
> +
>   		err = register_smmu_master(smmu, dev, &masterspec);
>   		if (err) {
>   			dev_err(dev, "failed to add master %s\n",
> @@ -1789,6 +1801,10 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev)
>
>   		i++;
>   	}
> +
> +	if (i == 0)
> +		goto out_put_masters;
> +
>   	dev_notice(dev, "registered %d master devices\n", i);
>
>   	parse_driver_options(smmu);
>