[RFC PATH 2/2] gpio: starfive-jh7100: Add StarFive JH7100 GPIO driver

[Matti Vaittinen]

Hi deee Ho Drew, Michael, All

On Mon, 2021-07-05 at 15:29 +0200, Michael Walle wrote:
> Hi Drew,
> 
> Am 2021-07-02 23:06, schrieb Drew Fustini:
> > On Fri, Jul 02, 2021 at 07:03:19PM +0300, Andy Shevchenko wrote:
> > > On Thu, Jul 1, 2021 at 3:23 AM Drew Fustini <drew at beagleboard.org
> > > > 
> > > wrote:
> > > > Add GPIO driver for the StarFive JH7100 SoC [1] used on the
> > > > BeagleV Starlight JH7100 board [2].
> > > > 
> > > > [1] https://github.com/starfive-tech/beaglev_doc/
> > > > [2] https://github.com/beagleboard/beaglev-starlight
> > > > Signed-off-by: Emil Renner Berthing <kernel at esmil.dk>
> > > > Signed-off-by: Huan Feng <huan.feng at starfivetech.com>
> > > > Signed-off-by: Drew Fustini <drew at beagleboard.org>
> > > 
> > > Seems some Co-developed-by are missing.
> > 
> > Thank you for suggesting this.  Huan Feng originally wrote the
> > driver.
> > Emil and I have made some changes to reorganize and clean it up for
> > submission.
> > 
> > Do you think all three of us should list Co-developed-by: for our
> > names
> > in addition to the SOB?
> > 
> > > Brief look into the code brings the Q. Can't you utilize gpio-
> > > regmap
> > > here? Why not?
> > 
> > Michael Walle asked about this yesterday and it was my first time
> > looking at regmap and gpio-regmap.  I've been reading the code and
> > it
> > does look like I should try convert this driver over to using
> > gpio-regmap.
> > 
> > The open question in my mind is how to handle the interrupt type
> > (edge
> > trigged on positive or negative, level triggered on high or low).
> > Hopefully I can find some other examples that can help me think
> > about
> > how to do that correctly.

> regmap_irq_type".
> If you're lucky, you can just supply the corresponding values that
> fits
> your hardware.

I added some level IRQ type-configuration support to regmap_irq back
when I wrote the BD70528 support. You should be able to just fill the
bit-mask indicating IRQ types supported by your GPIO controller
hardware, and then the corresponding type register values. As far as I
remember the supported types and values are given "per IRQ". If my
memory serves me right there was a limitation that the regmap-IRQ does
not distinguish setup where GPIO controller supports rising and falling
edges - but not both. That would have required adding another type
flag.

>  If it doesn't match your hardware at all, then you can
> keep your own functions, or if its slightly different, then maybe you
> can add support for your quirk in regmap-irq. You don't necessarily
> have
> to use regmap-irq together with gpio-regmap. You can also just use
> regmap-irq or gpio-regmap independently.
> 
> A quick grep for "type_rising_" lists drivers/mfd/max77650.c and
> drivers/mfd/rohm-bd70528.c for example.

The BD70528 has not been used too much and is scheduled for removal. It
may have received only limited testing but it *should* be functional
though.

Best Regards
	Matti Vaittinen