Re: [PATCH v1 1/1] i2c: cht-wc: Use fwnode for the controller and IRQ domain
From: Andy Shevchenko
Date: Thu Feb 25 2021 - 10:46:10 EST
On Thu, Feb 25, 2021 at 5:11 AM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
>
On 2/24/21 1:51 PM, Andy Shevchenko wrote:
>
> On Tue, Feb 23, 2021 at 08:25:35PM +0100, Hans de Goede wrote:
>
>> On 2/23/21 6:22 PM, Andy Shevchenko wrote:
>
>>> It's better to describe the I²C controller and associated IRQ domain with
>
>>> fwnode, so they will find their place in the hierarchy in sysfs and also
>
>>> make easier to debug.
...
>
>>> + set_primary_fwnode(&adap->adapter.dev, fwnode);
>
>>
>
>> So now we have the main PMIC device i2c-client, the platform-device instantiated
>
>> for the MFD-cell for the PMIC's builtin I2C-controller; and the device instantiated
>
>> for the adapter-device all 3 share the same ACPI-companion fwnode.
>
>
>
> Okay, this step in this patch maybe not needed (or should be a separate change,
>
> but I don't see clearly what would be the benefit out of it).
Shall I leave this or should be removed in v2?
...
>
>>> - adap->irq_domain = irq_domain_add_linear(pdev->dev.of_node, 1,
>
>>> - &irq_domain_simple_ops, NULL);
>
>>> + adap->irq_domain = irq_domain_create_linear(fwnode, 1,
>
>>> + &irq_domain_simple_ops, NULL);
>
>>
>
>> Hmm, not sure this is right, admittedly the old code looks weird too, but now we
>
>> are creating a second irq_domain at the same level as the irq_domain created for
>
>> the IRQ-chip part of the PMIC. But this is really more of a child-domain of just
>
>> the I2C-controller MFD-cell. The IRQ-CHIP part of the PMIC has a single IRQ for the
>
>> I2C controller which gets raised both on i2c-transfer completions and when the
>
>> pin on the PMIC which is reserved as input for the IRQ coming out of the charger-chip
>
>> gets triggered.
>
>>
>
>> IOW we have this:
>
>>
>
>>
>
>> PMIC
>
>> |
>
>> ------------------------------
>
>> | | | |
>
>> IRQ1 IRQ2 IRQ3 I2C-IRQ
>
>> |
>
>> ----------------------------------
>
>> | | | |
>
>> READIRQ WRIRQ NACKIRQ CLIENT-IRQ
>
>>
>
>> Where READIRQ, WRIRQ and NACKIRQ are directly consumed
>
>> and the CLIENT-IRQ is being represented as a single IRQ on
>
>> a new irqchip so that we can pass it along to the i2c-driver
>
>> for the charger-chip which is connected to the Whiskey Cove's
>
>> builtin I2C controller.
>
>>
>
>> But doing as you suggest would model the IRQs as:
>
>>
>
>> PMIC
>
>> |
>
>> --------------------------------------------------
>
>> | | | | |
>
>> IRQ1 IRQ2 IRQ3 I2C-IRQ CLIENT-IRQ
>
>>
>
>> Which is not the same really. I guess it is better then what we
>
>> have though ?
>
>
>
> Hmm... There should not be difference in the hierarchy. add_linear ==
>
> create_linear. The propagation of *device* (not an IRQ) fwnode is just
>
> convenient way to have IRQ domain be named (instead of 'unknown-N' or so).
>
> Maybe I have read __irq_domain_add() code wrongly.
>
>
Sorry, this is probably my bad. The first ASCII-art which I posted is
>
how things actually work in HW. The second one is how I assumed that
>
things would look like in some nested representation of the IRQ-domains
>
given that all the IRQs mentioned in the ASCII-art now use the same fwnode
>
as parent for their domain. But poking around in sysfs I don't see any
>
hierarchical representation of the domains at all. Actually I cannot
>
find any representation of the IRQ domains inside sysfs (I've never
>
looked at / into this before) ?
I have enabled GENERIC_IRQ_DEBUGFS to see some information.
>
If what you say is right and the fwnode is only used to set a name (where can
>
I see those names ?) then your patch is probably correct.
I have checked again and I don't see anything except it uses it as a
domain name and takes reference count.
>
> Nevertheless, thinking more about it, why we don't add an IRQ chip via regmap
>
> IRQ API?
>
>
There already is a regmap IRQ chip associated with the MFD device and the
>
IRQ handling required here is somewhat tricky (see the comments in the driver)
>
so I would prefer to keep this as is.
Ah, that makes things complicated a bit.
>
>> Note I can test any changes made here, but I'm not 100% convinced that
>
>> the current version of this patch is correct.
>
>
>
> If we settle on the idea first. I'm (slowly) looking forward to check another
>
> CherryTrail device we have at the lab, but we lack of some (power) equipment
>
> right now to setup it properly. I hope it may have the Whiskey Cove PMIC there.
>
>
More testing is always welcome :) With that said, testing these changes really
>
is not a lot of work for me.
I would expect that we will have a clash with IRQ domain names and
thus we would need our own fwnode here.
I will think about it, but it sounds like we need to create a
hierarchy of the IRQ domains and take the device's fwnode as a parent
here.
Overall, I stumbled over of_node use in pure ACPI case (simplest "fix"
is to provide a NULL pointer there). If you think we can get rid of
of_node as intermediate step, I will send v2 with that.
--
With Best Regards,
Andy Shevchenko