Re: [PATCH 1/2] dt-bindings: pinctrl: airoha: Add EN7581 pinctrl controller

[Andrew Lunn <andrew@xxxxxxx>]

On Sun, Aug 18, 2024 at 02:48:05PM +0200, Benjamin Larsson wrote:
> On 17/08/2024 23:39, Andrew Lunn wrote:
> > How messy are the GPIO and PWM registers? Are there N blocks of
> > independent GPIO registers? and M blocks of independent PWM registers?
> > By that, does one block of GPIO registers contain all you need for one
> > GPIO controller? One block of PWM registers give you all you need for
> > one PWM controller? Or are the registers for one GPIO controller
> > scattered all over the place?
> > 
> > Could you point at a public datasheet?
> > 
> >        Andrew
> > 
> Hi, per my understanding there is no public datasheet/register reference
> manual.
> 
> But here is the division of regions of the registers in the gpio block and
> how it is currently divided between the drivers (according to my current
> understanding).
> 
> 1FBF0200, gpio/pinctrl
> 1FBF0204, gpio/pinctrl
> 1FBF0208, gpio/pinctrl
> 1FBF020C, gpio/pinctrl
> 1FBF0210, gpio/pinctrl
> 1FBF0214, gpio/pinctrl

A typical SoC has multiple instances of a GPIO controller. Each GPIO
controller typically has 4 or 5 registers: In, Out, Direction,
Interrupt Enable, Interrupt Status. If these 4 or 5 registers are
contiguous, you could have one DT node per controller, rather than one
node for all GPIO controllers.

If the hardware designer has really messed up and fully interleaved
GPIO and PWM, it might be better to have an MFD. The MFD node has a
single reg covering the entire range. The MFD would then map the whole
range, and provide accessors to the child devices. Hard code the
knowledge of what registers are where. Given how badly the hardware is
designed, it is unlikely it will get reused in the future, so there is
no point putting lots of stuff into DT. Hard code it.

	Andrew