mirror of
https://github.com/zephyrproject-rtos/zephyr
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5a1313f804
In order to avoid bytes dropping when RTT output buffer is full, RTT session detection algorithm is introduced to the RTT console. If host session is detected console retries after wait state expecting host to empty the buffer. If host session is not detected console drops the byte without retrying. Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>
95 lines
2.1 KiB
C
95 lines
2.1 KiB
C
/* rtt_console.c - Console messages to a RAM buffer that is then read by
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* the Segger J-Link debugger
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*/
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/*
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* Copyright (c) 2016 Nordic Semiconductor ASA
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <kernel.h>
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#include <misc/printk.h>
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#include <device.h>
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#include <init.h>
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#include <rtt/SEGGER_RTT.h>
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extern void __printk_hook_install(int (*fn)(int));
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extern void __stdout_hook_install(int (*fn)(int));
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static bool host_present;
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/** @brief Wait for fixed period.
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*
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*/
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static void wait(void)
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{
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if (k_is_in_isr()) {
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if (IS_ENABLED(CONFIG_RTT_TX_RETRY_IN_INTERRUPT)) {
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k_busy_wait(1000*CONFIG_RTT_TX_RETRY_DELAY_MS);
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}
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} else {
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k_sleep(CONFIG_RTT_TX_RETRY_DELAY_MS);
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}
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}
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static int rtt_console_out(int character)
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{
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unsigned int key;
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char c = (char)character;
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unsigned int cnt;
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int max_cnt = CONFIG_RTT_TX_RETRY_CNT;
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do {
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key = irq_lock();
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cnt = SEGGER_RTT_WriteNoLock(0, &c, 1);
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irq_unlock(key);
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/* There are two possible reasons for not writing any data to
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* RTT:
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* - The host is not connected and not reading the data.
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* - The buffer got full and will be read by the host.
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* These two situations are distinguished using the following
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* algorithm:
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* At the beginning, the module assumes that the host is active,
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* so when no data is read, it busy waits and retries.
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* If, after retrying, the host reads the data, the module
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* assumes that the host is active. If it fails, the module
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* assumes that the host is inactive and stores that
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* information. On next call, only one attempt takes place.
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* The host is marked as active if the attempt is successful.
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*/
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if (cnt) {
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/* byte processed - host is present. */
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host_present = true;
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} else if (host_present) {
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if (max_cnt) {
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wait();
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max_cnt--;
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continue;
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} else {
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host_present = false;
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}
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}
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break;
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} while (1);
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return character;
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}
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static int rtt_console_init(struct device *d)
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{
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ARG_UNUSED(d);
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SEGGER_RTT_Init();
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__printk_hook_install(rtt_console_out);
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__stdout_hook_install(rtt_console_out);
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return 0;
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}
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SYS_INIT(rtt_console_init, PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);
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