linux-kernel - RE: [PATCH] gpio: dwapb: Add support for 32 interrupts

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Date:   Tue, 10 Apr 2018 06:24:24 +0000
From:   Phil Edworthy <phil.edworthy@...esas.com>
To:     Rob Herring <robh@...nel.org>
CC:     Hoan Tran <hotran@....com>,
        Linus Walleij <linus.walleij@...aro.org>,
        "Mark Rutland" <mark.rutland@....com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Michel Pollet <michel.pollet@...renesas.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] gpio: dwapb: Add support for 32 interrupts

Hi Rob,

On 09 April 2018 20:20 Rob Herring wrote:
> On Wed, Mar 28, 2018 at 03:22:30PM +0100, Phil Edworthy wrote:
> > The DesignWare GPIO IP can be configured for either 1 or 32
> > interrupts, but the driver currently only supports 1 interrupt. See
> > the DesignWare DW_apb_gpio Databook description of the
> 'GPIO_INTR_IO' parameter.
> 
> Someday h/w designers will realize this does nothing to optimize interrupt
> handling...
I can imagine some software where the isr is written to handle a specific GPIO
interrupt _could_ be faster, though no sane software would be designed like
that.

> > This change allows the driver to work with up to 32 interrupts, it
> > will get as many interrupts as specified in the DT 'interrupts' property.
> > It doesn't do anything clever with the different interrupts, it just
> > calls the same handler used for single interrupt hardware.
> >
> > Signed-off-by: Phil Edworthy <phil.edworthy@...esas.com>
> > ---
> > Note: There are a few lines over 80 chars, but this is just guidance, right?
> >       Especially as there are already some lines over 80 chars.
> 
> Code, yes, but not for paragraphs of text in DT bindings.
Good, that's what I did.

> > ---
> >  .../devicetree/bindings/gpio/snps-dwapb-gpio.txt   | 10 ++++-
> >  drivers/gpio/gpio-dwapb.c                          | 44 +++++++++++++++++-----
> >  include/linux/platform_data/gpio-dwapb.h           |  3 +-
> >  3 files changed, 45 insertions(+), 12 deletions(-)
> >
> > diff --git
> > a/Documentation/devicetree/bindings/gpio/snps-dwapb-gpio.txt
> > b/Documentation/devicetree/bindings/gpio/snps-dwapb-gpio.txt
> > index 4a75da7..e343581 100644
> > --- a/Documentation/devicetree/bindings/gpio/snps-dwapb-gpio.txt
> > +++ b/Documentation/devicetree/bindings/gpio/snps-dwapb-gpio.txt
> > @@ -26,8 +26,14 @@ controller.
> >    the second encodes the triger flags encoded as described in
> >
> > Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
> >  - interrupt-parent : The parent interrupt controller.
> > -- interrupts : The interrupt to the parent controller raised when
> > GPIOs
> > -  generate the interrupts.
> > +- interrupts : The interrupts to the parent controller raised when
> > +GPIOs
> > +  generate the interrupts. If the controller provides one combined
> > +interrupt
> > +  for all GPIOs, specify a single interrupt. If the controller
> > +provides one
> > +  interrupt for each GPIO, provide a list of interrupts that
> > +correspond to each
> > +  of the GPIO pins. When specifying multiple interrupts, if any of
> > +the GPIOs are
> > +  not connected to an interrupt, use the interrupt-mask property.
> > +- interrupt-mask : a 32-bit bit mask that specifies which interrupts
> > +in the list
> > +  of interrupts is valid, bit is 1 for a valid irq.
> 
> This is not a standard property and would need a vendor prefix. However, I'd
> prefer you just skip any not connected interrupts with an invalid interrupt
> number. Then the GPIO number is the index into "interrupts".
Makes sense, I'll rework it to do this.

> >  - snps,nr-gpios : The number of pins in the port, a single cell.
> 
> This BTW should be deprecated to use "nr-gpios" instead, but that's another
> patch.

Thanks for your comments,
Phil