linux-kernel - Re: [PATCH v2 2/4] regmap-irq: Add handle_mask

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Date:   Thu, 17 Nov 2022 10:00:17 -0500
From:   William Breathitt Gray <william.gray@...aro.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     linus.walleij@...aro.org, brgl@...ev.pl,
        andriy.shevchenko@...ux.intel.com, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org, michael@...le.cc
Subject: Re: [PATCH v2 2/4] regmap-irq: Add handle_mask_sync() callback

On Tue, Nov 15, 2022 at 05:14:14PM +0000, Mark Brown wrote:
> On Thu, Nov 10, 2022 at 08:55:51PM -0500, William Breathitt Gray wrote:
> 
> > Provide a public callback handle_mask_sync() that drivers can use when
> > they have more complex IRQ masking logic. The default implementation is
> > regmap_irq_handle_mask_sync(), used if the chip doesn't provide its own
> > callback.
> 
> Can you provide examples of something that would make sense to
> open code in a driver rather than factoring out?  It looks like
> this has been added due to one of the devices you're looking at
> for some reason disabling it's upstream interrupt when all of the
> downstream interrupts are masked, while weird that doesn't seem
> especally device specific.

Sure, I actually intend to use this callback for the 104-idi-48 module
as well in the v3 submission so I'll describe that situations well.

For the 104-dio-48e we have the following:

    Base Address +B (Write): Enable Interrupt
    Base Address +B (Read): Disable Interrupt
    Base Address +F (Read/Write): Clear Interrupt

So for 104-dio-48e, any write to 0xB will enable interrupts, while any
read will disable interrupts; interrupts are with either a read or any
write to 0xF. There's no status register either so software just has to
assume that if an interrupt is raised then it was for the
104-dio-48e device.

For the 104-idi-48, we do get a status register and some basic masking
but it's broken down by banks rather than individual GPIO; there are six
8-bit banks (Port 0 Low Byte, Port 0 Mid Byte, Port 0 High Byte, Port 1
Low Byte, Port 1 Mid Byte, Port 1 High Byte):

    Base Address + 0 (Read/Write): Port 0 Low Byte
    Base Address + 1 (Read/Write): Port 0 Mid Byte
    Base Address + 2 (Read/Write): Port 0 High Byte
    Base Address + 3: N/A
    Base Address + 4 (Read/Write): Port 1 Low Byte
    Base Address + 5 (Read/Write): Port 1 Mid Byte
    Base Address + 6 (Read/Write): Port 1 High Byte
    Base Address + 7 (Read): IRQ Status Register/IRQ Clear
        Bit 0-5: Respective Bank IRQ Statuses
        Bit 6: IRQ Status (Active Low)
        Bit 7: IRQ Enable Status
    Base Address + 7 (Write): IRQ Enable/Disable
        Bit 0-5: Respective Bank IRQ Enable/Disable

In this case, masking a bank will mask all 8 GPIO within that bank;
so ideally I want a way to only mask a bank when all GPIO are masked,
and unmasking when at least one is unmasked.

Are there existing ways to support these kinds of configuration in
regmap_irq?

William Breathitt Gray

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