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    SubjectRe: [PATCH 6/6] iommu/arm-smmu: Make use of phandle iterators in device-tree parsing
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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);
    >

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