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    SubjectRe: [PATCHv3 2/4] ARM: tegra: Add SMMU enabler in AHB
    Hi,

    On Thu, Apr 26, 2012 at 01:55:13PM -0600, Stephen Warren wrote:
    > On 04/25/2012 05:07 AM, Hiroshi DOYU wrote:
    > > Add extern func, "tegra_ahb_enable_smmu()" to inform AHB that SMMU is
    > > ready.
    >
    > > +#ifdef CONFIG_ARCH_TEGRA_3x_SOC
    > > +static int __tegra_ahb_enable_smmu(struct device *dev, void *data)
    > ...
    > > +int tegra_ahb_enable_smmu(void)
    > > +{
    > > + return driver_for_each_device(&tegra_ahb_driver.driver, NULL, NULL,
    > > + __tegra_ahb_enable_smmu);
    > > +}
    > > +EXPORT_SYMBOL(tegra_ahb_enable_smmu);
    > > +#endif
    >
    > That looks like a neat solution to avoid having a global device object.

    except that it won't work always. If you happen to have two AHB bridges,
    each using a separate smmu but only one smmu is ready, this will set
    SMMU_INIT_DONE on both bridges.

    > However, if that driver_for_each_device finds no devices, the function
    > still succeeds. That doesn't seem right, and doesn't allow e.g. the SMMU
    > to defer its probe until the AHB driver has completed.
    >
    > Perhaps add a local int variable to tegra_ahb_enable_smmu(), pass the
    > address to __tegra_ahb_enable_smmu, and have it increment the int. Then,
    > after calling driver_for_each_device,:
    >
    > if (!ahb_device_count)
    > return -EPROBE_DEFER
    > if (WARN_ON(ahb_device_count != 1))
    > return -EINVAL;
    > return 0;

    that would look, well, weird. Why don't you just different initcall
    leves for this ? Maybe smmu goes into postcore_initcall() and tegra_ahb
    goes into postcore_initcall_sync() ?? then you know that SMMU will be
    ready by the time you call tegra_ahb probe. Well, unless smmu's probe
    fail, but then again, IIUC it won't work anyway...

    --
    balbi
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