View source for Mainline:Broadcom Kona/Pin control (PADCTRL)

The pin controller in the BCM21664/BCM23550 appears to be ''somewhat'' similar to BCM28155, judging by the mainline driver.

* BCM21664 has '''155''' pins; each pin can also have '''6''' functions.
* BCM28155 has '''268''' pins; each pin can also have '''4''' functions.

The downstream pinmux driver is located at <code>arch/arm/plat-kona/pinmux.c</code>, with per-platform settings defined in <code>arch/arm/mach-{codename}/{codename}_pinmux.c</code>. These files also contain the init function <code>pinmux_chip_init()</code>, which on Java and Hawaii does two things: * unlocks the pinmux * allocates the memory for the pinmux driver to use

The pin controller/pinmux API, as well as a general explaination of how a pin controller works, can be found in the kernel documentation here: https://www.kernel.org/doc/html/latest/driver-api/pin-control.html (ah, if every component had a piece of docs like this...)

== Pin description ==

There are two ways in whicn pins are described in the downstream kernel (<code>arch/arm/mach-{codename}/{codename}_pinmux.c</code>): * using PIN_CFG and PIN_BSC_CFG, as seen in rhea. * using a custom <code>PIN_DESC</code> shorthand, as seen in hawaii/java; this wraps around <code>PIN_CFG</code>.

== Pins ==

There two types of pins: '''standard''' and '''I2C''' (BSC). BCM218XX driver in mainline also has a '''HDMI''' pin type.

== Functions ==

Each pin can have 6 alternative functions. The names (and thus numbers) for these are defined separately in the downstream drivers. They cover a lot more cases than just the base pins, including things like every GPIO. (This is a fairly standard pin muxing setup.)

The currently selected function is saved to the '''selector''' register, which represents the currently selected function in 3 bits. Which bit belongs to which function is described in <code>arch/arm/mach-{codename}/{codename}_pinmux.c</code>.