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SubjectRe: [PATCH v1] mfd: Add support for Merrifield Basin Cove PMIC
On Thu, 04 Apr 2019, Andy Shevchenko wrote:

> On Thu, Apr 04, 2019 at 08:03:57AM +0100, Lee Jones wrote:
> > On Thu, 04 Apr 2019, Lee Jones wrote:
> > > On Tue, 02 Apr 2019, Andy Shevchenko wrote:
> > > > On Tue, Apr 02, 2019 at 06:12:11AM +0100, Lee Jones wrote:
> > > > > On Mon, 18 Mar 2019, Andy Shevchenko wrote:
>
> > > > > > +static const struct mfd_cell bcove_dev[] = {
> > > > > > + {
> > > > > > + .name = "mrfld_bcove_pwrbtn",
> > > > > > + .num_resources = 1,
> > > > > > + .resources = &irq_level2_resources[0],
> > > > > > + }, {
> > > > > > + .name = "mrfld_bcove_tmu",
> > > > > > + .num_resources = 1,
> > > > > > + .resources = &irq_level2_resources[1],
> > > > > > + }, {
> > > > > > + .name = "mrfld_bcove_thermal",
> > > > > > + .num_resources = 1,
> > > > > > + .resources = &irq_level2_resources[2],
> > > > > > + }, {
> > > > > > + .name = "mrfld_bcove_bcu",
> > > > > > + .num_resources = 1,
> > > > > > + .resources = &irq_level2_resources[3],
> > > > > > + }, {
> > > > > > + .name = "mrfld_bcove_adc",
> > > > > > + .num_resources = 1,
> > > > > > + .resources = &irq_level2_resources[4],
> > > > > > + }, {
> > > > > > + .name = "mrfld_bcove_charger",
> > > > > > + .num_resources = 1,
> > > > > > + .resources = &irq_level2_resources[5],
> > > > > > + }, {
> > > > > > + .name = "mrfld_bcove_extcon",
> > > > > > + .num_resources = 1,
> > > > > > + .resources = &irq_level2_resources[5],
> > > > > > + }, {
> > > > > > + .name = "mrfld_bcove_gpio",
> > > > > > + .num_resources = 1,
> > > > > > + .resources = &irq_level2_resources[6],
> > > > > > + },
> > > > > > + { .name = "mrfld_bcove_region", },
> > > > > > +};
>
> > > > > > + for (i = 0; i < ARRAY_SIZE(irq_level2_resources); i++) {
> > > > > > + ret = platform_get_irq(pdev, i);
> > > > > > + if (ret < 0)
> > > > > > + return ret;
> > > > > > +
> > > > > > + irq_level2_resources[i].start = ret;
> > > > > > + irq_level2_resources[i].end = ret;
> > > > > > + }
> > > > >
> > > > > Although succinct, dragging values from one platform device into
> > > > > another doesn't sound that neat.
> > > >
> > > > So, how to split resources given in one _physical_ multi-functional device to
> > > > several of them? Isn't it what MFD framework for?
> > > >
> > > > Any other approach here? I'm all ears!
> > >
> > > From the child:
> > >
> > > platform_get_irq(dev->parent, CLIENT_ID);
>
> So, instead of keeping a fragile approach in one driver, we will spread this
> to all of them.

No, the fragileness goes away with implicit definitions of IDs.

> > If you set the .id of the cell properly you could do:
> >
> > platform_get_irq(dev->parent, dev->id);
>
> This will bring a confuse, ID is used to form an instance name, for now
> we don't have several instances of any of the devices from PMIC.

That is true. It is probably an abuse of the API. :)

I'm just floating ideas.

> On top of above, some of the resources (one already, others might be a case in
> the future) is split between two drivers, which would bring even more confusion
> to the entire picture.

I don't see any indication in the code that 2 platform devices can't
share the same .id value. But again, this is probably academic since
abusing the API should probably be avoided in general.

> > > > > Also, since the ordering of the
> > > > > devices is critical in this implementation, it also comes across as
> > > > > fragile.
> > > >
> > > > How fragile? In ACPI we don't have IRQ labeling scheme. Index is used for that.
> > > >
> > > > > Any reason why ACPI can't register all of the child devices, or for
> > > > > the child devices to obtain their IRQ directly from the tables?
> > > >
> > > > And how are we supposed to enumerated them taking into consideration single
> > > > ACPI ID given?
> > >
> > > This question was a little whimsical, since I have no idea how the
> > > ACPI tables you're working with are laid out.
>
> There is one device node with several IRQ and other resources.
> In pseudo code:
>
> device node {
> device ID,
> IRQ 0,
> IRQ 1,
> ...
> MMIO 0,
> ...
> }

Sure. Thanks for the explanation.

Very well. I guess it's not too bad as it is.

--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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