Date:   Mon, 21 Nov 2022 20:00:02 -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 Thu, Nov 17, 2022 at 10:00:17AM -0500, William Breathitt Gray wrote:
> 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

After trying to implement a handle_mask_sync() callback for the
104-idi-48 I discovered that it's not so straight-forward a task. The
mask_buf parameter is unsigned int so I can only represent 32 GPIO at a
time.

I could set the struct regmap_irq_chip num_regs member to '2' to
increase the number of mask_buf elements, but that creates side effects
because the regmap-irq API believes there there are more registers than
the device actually has.

For now with the 104-idi-48 module utilizing the regmap-irq API, we'll
have to leave it where masking one GPIO line masks the entire bank, and
vice versa for unmasking.

William Breathitt Gray

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