diff options
Diffstat (limited to 'drivers/console/aarch64/skeleton_console.S')
| -rw-r--r-- | drivers/console/aarch64/skeleton_console.S | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/drivers/console/aarch64/skeleton_console.S b/drivers/console/aarch64/skeleton_console.S new file mode 100644 index 0000000..7ea2eec --- /dev/null +++ b/drivers/console/aarch64/skeleton_console.S @@ -0,0 +1,170 @@ +/* + * Copyright (c) 2015-2020, ARM Limited and Contributors. All rights reserved. + * + * SPDX-License-Identifier: BSD-3-Clause + */ +#include <asm_macros.S> +#include <console_macros.S> + + /* + * This file contains a skeleton console driver that can be used as a + * basis for a real console driver. Console drivers in Trusted Firmware + * can be instantiated multiple times. Each instance is described by a + * separate console_t structure which must be registered with the common + * console framework via console_register(). Console drivers should + * define a console_xxx_register() function that initializes a new + * console_t structure passed in from the caller and registers it after + * initializing the console hardware. Drivers may define their own + * structures extending console_t to store private driver information. + * Console drivers *MUST* ensure that the console callbacks they + * implement only change registers allowed in the clobber lists defined + * in this file. (Note that in addition to the explicit clobber lists, + * any function may always clobber the intra-procedure-call registers + * X16 and X17, but may never depend on them retaining their values + * across any function call.) + */ + + .globl console_xxx_register + .globl console_xxx_putc + .globl console_xxx_getc + .globl console_xxx_flush + + /* ----------------------------------------------- + * int console_xxx_register(console_xxx_t *console, + * ...additional parameters as desired...) + * Function to initialize and register the console. + * The caller needs to pass an empty console_xxx_t + * structure in which *MUST* be allocated in + * persistent memory (e.g. a global or static local + * variable, *NOT* on the stack). + * In : x0 - pointer to empty console_t structure + * x1 through x7: additional parameters as desired + * Out: x0 - 1 on success, 0 on error + * Clobber list : x0 - x7 + * ----------------------------------------------- + */ +func console_xxx_register + /* + * Store parameters (e.g. hardware base address) in driver-specific + * console_xxx_t structure field if they will need to be retrieved + * by later console callback (e.g. putc). + * Example: + */ + str x1, [x0, #CONSOLE_T_BASE] + str x2, [x0, #CONSOLE_T_XXX_SOME_OTHER_VALUE] + + /* + * Initialize console hardware, using x1 - x7 parameters as needed. + * Keep console_t pointer in x0 for later. + */ + + /* + * Macro to finish up registration and return (needs valid x0 + x30). + * If any of the argument is unspecified, then the corresponding + * entry in console_t is set to 0. + */ + finish_console_register xxx putc=1, getc=1, flush=1 + + /* Jump here if hardware init fails or parameters are invalid. */ +register_fail: + mov w0, #0 + ret +endfunc console_xxx_register + + /* -------------------------------------------------------- + * int console_xxx_putc(int c, console_xxx_t *console) + * Function to output a character over the console. It + * returns the character printed on success or -1 on error. + * In : w0 - character to be printed + * x1 - pointer to console_t struct + * Out: w0 - printed character on success, < 0 on error. + * Clobber list : x0, x1, x2 + * -------------------------------------------------------- + */ +func console_xxx_putc + /* + * Retrieve values we need (e.g. hardware base address) from + * console_xxx_t structure pointed to by x1. + * Example: + */ + ldr x1, [x1, #CONSOLE_T_BASE] + + /* + * Write w0 to hardware. + */ + + ret + + /* Jump here if output fails for any reason. */ +putc_error: + mov w0, #-1 + ret +endfunc console_xxx_putc + + /* --------------------------------------------- + * int console_xxx_getc(console_xxx_t *console) + * Function to get a character from the console. + * Even though console_getc() is blocking, this + * callback has to be non-blocking and always + * return immediately to allow polling multiple + * drivers concurrently. + * Returns the character grabbed on success, + * ERROR_NO_PENDING_CHAR if no character was + * available at this time, or any value + * between -2 and -127 if there was an error. + * In : x0 - pointer to console_t struct + * Out: w0 - character on success, + * ERROR_NO_PENDING_CHAR if no char, + * < -1 on error + * Clobber list : x0, x1 + * --------------------------------------------- + */ +func console_xxx_getc + /* + * Retrieve values we need (e.g. hardware base address) from + * console_xxx_t structure pointed to by x0. + * Example: + */ + ldr x1, [x0, #CONSOLE_T_BASE] + + /* + * Try to read character into w0 from hardware. + */ + + ret + + /* Jump here if there is no character available at this time. */ +getc_no_char: + mov w0, #ERROR_NO_PENDING_CHAR + ret + + /* Jump here if there was any hardware error. */ +getc_error: + mov w0, #-2 /* may pick error codes between -2 and -127 */ + ret +endfunc console_xxx_getc + + /* --------------------------------------------- + * void console_xxx_flush(console_xxx_t *console) + * Function to force a write of all buffered + * data that hasn't been output. + * In : x0 - pointer to console_xxx_t struct + * Out: void + * Clobber list : x0, x1, x2, x3, x4, x5 + * --------------------------------------------- + */ +func console_xxx_flush + /* + * Retrieve values we need (e.g. hardware base address) from + * console_xxx_t structure pointed to by x0. + * Example: + */ + ldr x1, [x0, #CONSOLE_T_BASE] + + /* + * Flush all remaining output from hardware FIFOs. Do not return until + * all data has been flushed or there was an unrecoverable error. + */ + + ret +endfunc console_xxx_flush |