On 07/08/2013 07:02 AM, Christian Ruppert wrote:
...
> OK, a small drawing of our hardware should make this clear, let's take
> an imaginary example of one port with 10 pins, one i2c interface, one
> spi interface and one GPIO bank:
>
> | mux N-1|
> +........+
> | | 2
> | +--/-- i2c
> | |
> 10 | | 4
> Pins --/--+ mux N +--/-- spi
> | |
> | | 10
> | +--/-- GPIO
> | |
> +........+
> | mux N+1|
>
> This example shows the mux N inside the pin controller. It controls
> all pins associated to port N through a single register value M. Let's
> assume the pins are configured as follows in function of the register
> value:
>
> pin M=0 M=1 M=2 M=3
> 0 GPIO0 SPI_MISO GPIO0 SPI_MISO
> 1 GPIO1 SPI_MOSI GPIO1 SPI_MOSI
> 2 GPIO2 SPI_CK GPIO2 SPI_CK
> 3 GPIO3 SPI_CS GPIO3 SPI_CS
> 4 GPIO4 GPIO4 GPIO4 GPIO4
> 5 GPIO5 GPIO5 GPIO5 GPIO5
> 6 GPIO6 GPIO6 GPIO6 GPIO6
> 7 GPIO7 GPIO7 GPIO7 GPIO7
> 8 GPIO8 GPIO8 I2C_SDA I2C_SDA
> 9 GPIO9 GPIO9 I2C_SCL I2C_SCL
In that scenario, in the language of Linux's pinctrl subsystem, what you
have is:
10 pins, named 0..9
1 pin group, named perhaps "mux N".
4 different functions; values M==0, 1, 2, 3.
> We now have three pin groups defined, corresponding to the chip-side
> ports of the pin controller:
> GPIO = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
> SPI = {0, 1, 2, 3}
> I2C = {8, 9}
You would usually only define pin groups for the pin/ball/package side
of the pinmux HW. IIRC, you're also wanting to define pin groups for the
intra-chip side of the pinmux HW. However, you're not muxing functions
onto those pingroups; they're just there to help with naming the
GPIO<->pinmux mapping. You only mux functions onto the pin/ball/package
side pins/pingroups.
> abilis,pingrp now specifies one of the three pin groups. Note that I2C
> and SPI can be requested independently in a completely orthogonal
> manner: The information if I2C is reqired or not is confined to
> the I2C request and does not leak into the SPI request as would
> be the case if we configured the entire port at the same time.
The pingrp should represent the pin/ball/package side pins/groups. In
this case, it should specify "N".
> abilis,ioport specifies N.
That is replaced be pingrp.
> abilis,ioconf specifies M.
That'd be better named "function" or something like that, in order to
indicate that it specifies which function is mux'd onto the specified
pin(s)/pingroup(s).
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