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diff --git a/doc/README.AVR32-port-muxing b/doc/README.AVR32-port-muxing deleted file mode 100644 index 8c1718cdca..0000000000 --- a/doc/README.AVR32-port-muxing +++ /dev/null @@ -1,208 +0,0 @@ -AVR32 Port multiplexer configuration -==================================== - -On AVR32 chips, most external I/O pins are routed through a port -multiplexer. There are currently two kinds of port multiplexer -hardware around with different register interfaces: - - * PIO (AT32AP700x; this is also used on ARM AT91 chips) - * GPIO (all other AVR32 chips) - -The "PIO" variant supports multiplexing up to two peripherals per pin -in addition to GPIO (software control). Each pin has configurable -pull-up, glitch filter, interrupt and multi-drive capabilities. - -The "GPIO" variant supports multiplexing up to four peripherals per -pin in addition to GPIO. Each pin has configurable -pull-up/pull-down/buskeeper, glitch filter, interrupt, open-drain and -schmitt-trigger capabilities, as well as configurable drive strength -and slew rate control. - -Both controllers are configured using the same API, but the functions -may accept different values for some parameters depending on the -actual portmux implementation, and some parameters may be ignored by -one of the implementation (e.g. the "PIO" implementation will ignore -the drive strength flags since the hardware doesn't support -configurable drive strength.) - -Selecting the portmux implementation ------------------------------------- -Since u-boot is lacking a Kconfig-style configuration engine, the -portmux implementation must be selected manually by defining one of -the following symbols: - - CONFIG_PORTMUX_PIO - CONFIG_PORTMUX_GPIO - -depending on which implementation the chip in question uses. - -Identifying pins ----------------- -The portmux configuration functions described below identify the pins -to act on based on two parameters: A "port" (i.e. a block of pins -that somehow belong together) and a pin mask. Both are defined in an -implementation-specific manner. - -The available ports are defined on the form - - #define PORTMUX_PORT_A (something) - -where "A" matches the identifier given in the chip's data sheet, and -"something" is whatever the portmux implementation needs to identify -the port (usually a memory address). - -The pin mask is a bitmask where each '1' bit indicates a pin to apply -the current operation to. The width of the bitmask may vary from port -to port, but it is never wider than 32 bits (which is the width of -'unsigned long' on avr32). - -Selecting functions -------------------- -Each pin can either be assigned to one of a predefined set of on-chip -peripherals, or it can be set up to be controlled by software. For the -former case, the portmux implementation defines an enum containing all -the possible peripheral functions that can be selected. For example, -the PIO implementation, which allows multiplexing two peripherals per -pin, defines it like this: - - enum portmux_function { - PORTMUX_FUNC_A, - PORTMUX_FUNC_B, - }; - -To configure a set of pins to be connected to a given peripheral -function, the following function is used. - - void portmux_select_peripheral(void *port, unsigned long pin_mask, - enum portmux_function func, unsigned long flags); - -To configure a set of pins to be controlled by software (GPIO), the -following function is used. In this case, no "function" argument is -required since "GPIO" is a function in its own right. - - void portmux_select_gpio(void *port, unsigned int pin_mask, - unsigned long flags); - -Both of these functions take a "flags" parameter which may be used to -alter the default configuration of the pin. This is a bitmask of -various flags defined in an implementation-specific way, but the names -of the flags are the same on all implementations. - - PORTMUX_DIR_OUTPUT - PORTMUX_DIR_INPUT - -These mutually-exclusive flags configure the initial direction of the -pins. PORTMUX_DIR_OUTPUT means that the pins are driven by the CPU, -while PORTMUX_DIR_INPUT means that the pins are tristated by the CPU. -These flags are ignored by portmux_select_peripheral(). - - PORTMUX_INIT_HIGH - PORTMUX_INIT_LOW - -These mutually-exclusive flags configure the initial state of the -pins: High (Vdd) or low (Vss). They are only effective when -portmux_select_gpio() is called with the PORTMUX_DIR_OUTPUT flag set. - - PORTMUX_PULL_UP - PORTMUX_PULL_DOWN - PORTMUX_BUSKEEPER - -These mutually-exclusive flags are used to enable any on-chip CMOS -resistors connected to the pins. PORTMUX_PULL_UP causes the pins to be -pulled up to Vdd, PORTMUX_PULL_DOWN causes the pins to be pulled down -to Vss, and PORTMUX_BUSKEEPER will keep the pins in whatever state -they were left in by whatever was driving them last. If none of the -flags are specified, the pins are left floating if no one are driving -them; this is only recommended for always-output pins (e.g. extern -address and control lines driven by the CPU.) - -Note that the "PIO" implementation will silently ignore the -PORTMUX_PULL_DOWN flag and interpret PORTMUX_BUSKEEPER as -PORTMUX_PULL_UP. - - PORTMUX_DRIVE_MIN - PORTMUX_DRIVE_LOW - PORTMUX_DRIVE_HIGH - PORTMUX_DRIVE_MAX - -These mutually-exclusive flags determine the drive strength of the -pins. PORTMUX_DRIVE_MIN will give low power-consumption, but may cause -corruption of high-speed signals. PORTMUX_DRIVE_MAX will give high -power-consumption, but may be necessary on pins toggling at very high -speeds. PORTMUX_DRIVE_LOW and PORTMUX_DRIVE_HIGH specify something in -between the other two. - -Note that setting the drive strength too high may cause excessive -overshoot and EMI problems, which may in turn cause signal corruption. -Also note that the "PIO" implementation will silently ignore these -flags. - - PORTMUX_OPEN_DRAIN - -This flag will configure the pins as "open drain", i.e. setting the -pin state to 0 will drive it low, while setting it to 1 will leave it -floating (or, in most cases, let it be pulled high by an internal or -external pull-up resistor.) In the data sheet for chips using the -"PIO" variant, this mode is called "multi-driver". - -Enabling specific peripherals ------------------------------ -In addition to the above functions, each chip provides a set of -functions for setting up the port multiplexer to use a given -peripheral. The following are some of the functions available. - -All the functions below take a "drive_strength" parameter, which must -be one of the PORTMUX_DRIVE_x flags specified above. Any other -portmux flags will be silently filtered out. - -To set up the External Bus Interface (EBI), call - - void portmux_enable_ebi(unsigned int bus_width, - unsigned long flags, unsigned long drive_strength) - -where "bus_width" must be either 16 or 32. "flags" can be any -combination of the following flags. - - PORTMUX_EBI_CS(x) /* Enable chip select x */ - PORTMUX_EBI_NAND /* Enable NAND flash interface */ - PORTMUX_EBI_CF(x) /* Enable CompactFlash interface x */ - PORTMUX_EBI_NWAIT /* Enable NWAIT signal */ - -To set up a USART, call - - void portmux_enable_usartX(unsigned long drive_strength); - -where X is replaced by the USART instance to be configured. - -To set up an ethernet MAC: - - void portmux_enable_macbX(unsigned long flags, - unsigned long drive_strength); - -where X is replaced by the MACB instance to be configured. "flags" can -be any combination of the following flags. - - PORTMUX_MACB_RMII /* Just set up the RMII interface */ - PORTMUX_MACB_MII /* Set up full MII interface */ - PORTMUX_MACB_SPEED /* Enable the SPEED pin */ - -To set up the MMC controller: - - void portmux_enable_mmci(unsigned long slot, unsigned long flags - unsigned long drive_strength); - -where "slot" identifies which of the alternative SD card slots to -enable. "flags" can be any combination of the following flags: - - PORTMUX_MMCI_4BIT /* Enable 4-bit SD card interface */ - PORTMUX_MMCI_8BIT /* Enable 8-bit MMC+ interface */ - PORTMUX_MMCI_EXT_PULLUP /* Board has external pull-ups */ - -To set up a SPI controller: - - void portmux_enable_spiX(unsigned long cs_mask, - unsigned long drive_strength); - -where X is replaced by the SPI instance to be configured. "cs_mask" is -a 4-bit bitmask specifying which of the four standard chip select -lines to set up as GPIOs. |