On Wed, Jan 07, 2026 at 03:35:45PM +0100, Geert Uytterhoeven wrote:
> Hi Stafford,
>
> On Wed, 17 Dec 2025 at 09:15, Stafford Horne <[email protected]> wrote:
> > In FPGA Development boards with GPIOs we use the opencores gpio verilog
> > rtl. This is compatible with the gpio-mmio. Add the compatible string
> > to allow as below.
> >
> > Example:
> >
> > gpio0: gpio@91000000 {
> > compatible = "opencores,gpio", "brcm,bcm6345-gpio";
> > reg = <0x91000000 0x1>, <0x91000001 0x1>;
> > reg-names = "dat", "dirout";
> > gpio-controller;
> > #gpio-cells = <2>;
> > status = "okay";
> > };
> >
> > Link: https://opencores.org/projects/gpio
> > Signed-off-by: Stafford Horne <[email protected]>
>
> Thanks for your patch, which is now commit f48b5e8bc2e1344f
> ("dt-bindings: gpio-mmio: Add compatible string for opencores,gpio")
> in gpio/gpio/for-next.
>
> > --- a/Documentation/devicetree/bindings/gpio/gpio-mmio.yaml
> > +++ b/Documentation/devicetree/bindings/gpio/gpio-mmio.yaml
> > @@ -18,11 +18,16 @@ description:
> >
> > properties:
> > compatible:
> > - enum:
> > - - brcm,bcm6345-gpio
> > - - ni,169445-nand-gpio
> > - - wd,mbl-gpio # Western Digital MyBook Live memory-mapped GPIO
> > controller
> > - - intel,ixp4xx-expansion-bus-mmio-gpio
> > + oneOf:
> > + - enum:
> > + - brcm,bcm6345-gpio
> > + - ni,169445-nand-gpio
> > + - wd,mbl-gpio # Western Digital MyBook Live memory-mapped GPIO
> > controller
> > + - intel,ixp4xx-expansion-bus-mmio-gpio
> > + - items:
> > + - enum:
> > + - opencores,gpio
> > + - const: brcm,bcm6345-gpio
>
> What is the rationale behind using brcm,bcm6345-gpio?
> Given brcm,bcm6345-gpio has 32-bit registers, while opencores,gpio
> has 8-bit registers, I doubt the latter is compatible with the former...
Hello,
I was following what we did for uart, where we have
"opencores,uart16550-rtlsvn105", "ns16550a".
I am using brcm,bcm6345-gpio to match the drivers/gpio/gpio-mmio.c driver.
The opencores,gpio is compatible with the same driver as brcm,bcm6345-gpio but
not 100% the same as the brcm,bcm6345-gpio. Since the device tree allows
configuring the gpio-mmio driver to make it compatible with opencore,gpio I
thought this would be OK.
I switch the size from 32-bit to 8-bit using the reg = <* 0x1>, <* 0x1> setting.
Also the reg addresses of "dat" and "dirout" are different for the real
brcm,bcm6345-gpio.
brcm,bcm6345-gpio. Example:
/* GPIOs 192 .. 223 */
gpio6: gpio@518 {
compatible = "brcm,bcm6345-gpio";
reg = <0x518 0x04>, <0x538 0x04>;
reg-names = "dirout", "dat";
gpio-controller;
#gpio-cells = <2>;
};
vs opencores,gpio Example:
gpio0: gpio@91000000 {
compatible = "opencores,gpio", "brcm,bcm6345-gpio";
reg = <0x91000000 0x1>, <0x91000001 0x1>;
reg-names = "dat", "dirout";
gpio-controller;
#gpio-cells = <2>;
};
The opencores,gpio setup does work.
Now that I think about it, would it have been better to just add opencores,gpio
to gpio-mmio.c compatible list?
If so I will can revise this patch and add patch to gpio-mmio.c.
-Stafford
