On Tuesday 23 September 2014 15:59:43 Pankaj Dubey wrote:
> > > -static int syscon_match_node(struct device *dev, void *data)
> > > +static struct syscon *of_syscon_register(struct device_node *np)
> > > {
> > > - struct device_node *dn = data;
> > > + struct platform_device *pdev = NULL;
> > > + struct syscon *syscon;
> > > + struct regmap *regmap;
> > > + void __iomem *base;
> > > + int ret;
> > > +
> > > + if (!of_device_is_compatible(np, "syscon"))
> > > + return ERR_PTR(-EINVAL);
> > > +
> > > + syscon = kzalloc(sizeof(*syscon), GFP_KERNEL);
> > > + if (!syscon)
> > > + return ERR_PTR(-ENOMEM);
> > > +
> > > + base = of_iomap(np, 0);
> > > + if (!base) {
> > > + ret = -ENOMEM;
> > > + goto err_map;
> > > + }
> > > +
> > > + /* if device is already populated and available then use it */
> > > + pdev = of_find_device_by_node(np);
> > > + if (!pdev) {
> > > + /* for early users create dummy syscon device and use it */
> > > + pdev = platform_device_alloc("dummy-syscon", -1);
> >
> > Can we create specific devices for each syscon device?
> > That looks more reasonable to me.
> > Then we can dump registers in regmap debugfs more clearly, just like other
> devices.
> > And i think it's better to follow device tree way to generate devices from
> node.
> > If DT core find a device is already created, it can ignore that device to
> avoid creating
> > duplicated device during of_platform_populate.
> >
>
> If you are referring to use "of_platform_device_create", then I am afraid
> that it can't be used
> in very early stage. For example, current patch I tested by calling
> syscon_lookup_by_phandle from
> "init_irq" hook of machine_desc, and it worked well, but If I use
> "of_platform_device_create"
> instead of dummy device, it fails to create pdev and this I verified on
> Exynos platform. The reason
> I selected "init_irq" is because this comes just before smp init and where
> once we tried to get regmap handle,
> but could not do so.
I don't remember noticing the of_find_device_by_node or platform_device_alloc
in earlier versions of this patch, but that could just be me failing to
read it right.
I think this should get removed: it would be much better to ensure that
the regmap code can work without a device pointer, which I thought it
did. We should probably also skip the creation of the debugfs directory
in that case.
> Also if it was just a matter of creating platform_device at early stage then
> early initialization of
> syscon could have been solved till now.
>
> So I would suggest if we really want this patch to cover early
> initialization of syscon
> (which is not it's main purpose) current patch is sufficient.
>
> @Arnd, since I have addressed crash issue as reported by Dong Aisheng, I
> would like to take your ack,
> but since there are some more code changes other than what you suggested I
> request you to check this
> and if you are ok, then I would like to your ack so that I can request to
> maintainer for taking this patch.
I think we first need to resolve the question of the platform device.
Arnd
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