1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * POWER Data Stream Control Register (DSCR) explicit test
  4 *
  5 * This test modifies the DSCR value using mtspr instruction and
  6 * verifies the change with mfspr instruction. It uses both the
  7 * privilege state SPR and the problem state SPR for this purpose.
  8 *
  9 * When using the privilege state SPR, the instructions such as
 10 * mfspr or mtspr are privileged and the kernel emulates them
 11 * for us. Instructions using problem state SPR can be executed
 12 * directly without any emulation if the HW supports them. Else
 13 * they also get emulated by the kernel.
 14 *
 15 * Copyright 2012, Anton Blanchard, IBM Corporation.
 16 * Copyright 2015, Anshuman Khandual, IBM Corporation.
 17 */
 18
 19#define _GNU_SOURCE
 20
 21#include "dscr.h"
 22#include "utils.h"
 23
 24#include <pthread.h>
 25#include <sched.h>
 26#include <semaphore.h>
 27
 28void *dscr_explicit_lockstep_thread(void *args)
 29{
 30	sem_t *prev = (sem_t *)args;
 31	sem_t *next = (sem_t *)args + 1;
 32	unsigned long expected_dscr = 0;
 33
 34	set_dscr(expected_dscr);
 35	srand(gettid());
 36
 37	for (int i = 0; i < COUNT; i++) {
 38		FAIL_IF_EXIT(sem_wait(prev));
 39
 40		FAIL_IF_EXIT(expected_dscr != get_dscr());
 41		FAIL_IF_EXIT(expected_dscr != get_dscr_usr());
 42
 43		expected_dscr = (expected_dscr + 1) % DSCR_MAX;
 44		set_dscr(expected_dscr);
 45
 46		FAIL_IF_EXIT(sem_post(next));
 47	}
 48
 49	return NULL;
 50}
 51
 52int dscr_explicit_lockstep_test(void)
 53{
 54	pthread_t thread;
 55	sem_t semaphores[2];
 56	sem_t *prev = &semaphores[1];  /* reversed prev/next than for the other thread */
 57	sem_t *next = &semaphores[0];
 58	unsigned long expected_dscr = 0;
 59
 60	SKIP_IF(!have_hwcap2(PPC_FEATURE2_DSCR));
 61
 62	srand(gettid());
 63	set_dscr(expected_dscr);
 64
 65	FAIL_IF(sem_init(prev, 0, 0));
 66	FAIL_IF(sem_init(next, 0, 1));  /* other thread starts first */
 67	FAIL_IF(bind_to_cpu(BIND_CPU_ANY) < 0);
 68	FAIL_IF(pthread_create(&thread, NULL, dscr_explicit_lockstep_thread, (void *)semaphores));
 69
 70	for (int i = 0; i < COUNT; i++) {
 71		FAIL_IF(sem_wait(prev));
 72
 73		FAIL_IF(expected_dscr != get_dscr());
 74		FAIL_IF(expected_dscr != get_dscr_usr());
 75
 76		expected_dscr = (expected_dscr - 1) % DSCR_MAX;
 77		set_dscr(expected_dscr);
 78
 79		FAIL_IF(sem_post(next));
 80	}
 81
 82	FAIL_IF(pthread_join(thread, NULL));
 83	FAIL_IF(sem_destroy(prev));
 84	FAIL_IF(sem_destroy(next));
 85
 86	return 0;
 87}
 88
 89struct random_thread_args {
 90	pthread_t thread_id;
 91	bool do_yields;
 92	pthread_barrier_t *barrier;
 93};
 94
 95void *dscr_explicit_random_thread(void *in)
 96{
 97	struct random_thread_args *args = (struct random_thread_args *)in;
 98	unsigned long expected_dscr = 0;
 99	int err;
100
101	srand(gettid());
102
103	err = pthread_barrier_wait(args->barrier);
104	FAIL_IF_EXIT(err != 0 && err != PTHREAD_BARRIER_SERIAL_THREAD);
105
106	for (int i = 0; i < COUNT; i++) {
107		expected_dscr = rand() % DSCR_MAX;
108		set_dscr(expected_dscr);
109
110		for (int j = rand() % 5; j > 0; --j) {
111			FAIL_IF_EXIT(get_dscr() != expected_dscr);
112			FAIL_IF_EXIT(get_dscr_usr() != expected_dscr);
113
114			if (args->do_yields && rand() % 2)
115				sched_yield();
116		}
117
118		expected_dscr = rand() % DSCR_MAX;
119		set_dscr_usr(expected_dscr);
120
121		for (int j = rand() % 5; j > 0; --j) {
122			FAIL_IF_EXIT(get_dscr() != expected_dscr);
123			FAIL_IF_EXIT(get_dscr_usr() != expected_dscr);
124
125			if (args->do_yields && rand() % 2)
126				sched_yield();
127		}
128	}
129
130	return NULL;
131}
132
133int dscr_explicit_random_test(void)
134{
135	struct random_thread_args threads[THREADS];
136	pthread_barrier_t barrier;
137
138	SKIP_IF(!have_hwcap2(PPC_FEATURE2_DSCR));
139
140	FAIL_IF(pthread_barrier_init(&barrier, NULL, THREADS));
141
142	for (int i = 0; i < THREADS; i++) {
143		threads[i].do_yields = i % 2 == 0;
144		threads[i].barrier = &barrier;
145
146		FAIL_IF(pthread_create(&threads[i].thread_id, NULL,
147				       dscr_explicit_random_thread, (void *)&threads[i]));
148	}
149
150	for (int i = 0; i < THREADS; i++)
151		FAIL_IF(pthread_join(threads[i].thread_id, NULL));
152
153	FAIL_IF(pthread_barrier_destroy(&barrier));
154
155	return 0;
156}
157
158int main(int argc, char *argv[])
159{
160	unsigned long orig_dscr_default = 0;
161	int err = 0;
162
163	if (have_hwcap2(PPC_FEATURE2_DSCR))
164		orig_dscr_default = get_default_dscr();
165
166	err |= test_harness(dscr_explicit_lockstep_test, "dscr_explicit_lockstep_test");
167	err |= test_harness(dscr_explicit_random_test, "dscr_explicit_random_test");
168
169	if (have_hwcap2(PPC_FEATURE2_DSCR))
170		set_default_dscr(orig_dscr_default);
171
172	return err;
173}