feat: add helper functions for SP sleep
This patch introduces new helper utilities: virtualcounter_read() and
sp_sleep_elapsed_time() which are further used in sp_sleep() utility.
This patch also adds a needed isb when reading the virtual counter,
to prevent reading stale values, as well as reducing the number of
reads of the virtual counter required. Refer Arm ARM D11.2.2
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: Icaf1777e85ee2efc043bfa83d630edf54bf5a099
diff --git a/include/lib/aarch64/arch_helpers.h b/include/lib/aarch64/arch_helpers.h
index 696cd01..8287422 100644
--- a/include/lib/aarch64/arch_helpers.h
+++ b/include/lib/aarch64/arch_helpers.h
@@ -562,4 +562,16 @@
return read_cntpct_el0();
}
+/* Read the value of the Counter-timer virtual count. */
+static inline uint64_t virtualcounter_read(void)
+{
+ /*
+ * The instruction barrier is needed to guarantee that we read an
+ * accurate value. Otherwise, the CPU might speculatively read it and
+ * return a stale value.
+ */
+ isb();
+ return read_cntvct_el0();
+}
+
#endif /* ARCH_HELPERS_H */
diff --git a/spm/cactus/cactus_tests/cactus_test_interrupts.c b/spm/cactus/cactus_tests/cactus_test_interrupts.c
index b675dfc..aa39ef2 100644
--- a/spm/cactus/cactus_tests/cactus_test_interrupts.c
+++ b/spm/cactus/cactus_tests/cactus_test_interrupts.c
@@ -13,18 +13,16 @@
CACTUS_CMD_HANDLER(sleep_cmd, CACTUS_SLEEP_CMD)
{
- uint64_t timer_freq = read_cntfrq_el0();
- uint64_t time1, time2, time_lapsed;
+ uint64_t time_lapsed;
uint32_t sleep_time = cactus_get_sleep_time(*args);
- VERBOSE("Request to sleep %x for %ums.\n", ffa_dir_msg_dest(*args), sleep_time);
+ VERBOSE("Request to sleep %x for %ums.\n", ffa_dir_msg_dest(*args),
+ sleep_time);
- time1 = read_cntvct_el0();
- sp_sleep(sleep_time);
- time2 = read_cntvct_el0();
+ time_lapsed = sp_sleep_elapsed_time(sleep_time);
- /* Lapsed time should be at least equal to sleep time */
- time_lapsed = ((time2 - time1) * 1000) / timer_freq;
+ /* Lapsed time should be at least equal to sleep time. */
+ VERBOSE("Sleep complete: %llu\n", time_lapsed);
return cactus_response(ffa_dir_msg_dest(*args),
ffa_dir_msg_source(*args),
diff --git a/spm/common/sp_helpers.c b/spm/common/sp_helpers.c
index a6b6bc5..77031f8 100644
--- a/spm/common/sp_helpers.c
+++ b/spm/common/sp_helpers.c
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2018, Arm Limited. All rights reserved.
+ * Copyright (c) 2018-2021, Arm Limited. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
@@ -58,16 +58,25 @@
INFO("Test \"%s\" end.\n", test_desc);
}
-void sp_sleep(uint32_t ms)
+uint64_t sp_sleep_elapsed_time(uint32_t ms)
{
uint64_t timer_freq = read_cntfrq_el0();
VERBOSE("%s: Timer frequency = %llu\n", __func__, timer_freq);
VERBOSE("%s: Sleeping for %u milliseconds...\n", __func__, ms);
- uint64_t time1 = read_cntvct_el0();
+
+ uint64_t time1 = virtualcounter_read();
volatile uint64_t time2 = time1;
+
while ((time2 - time1) < ((ms * timer_freq) / 1000U)) {
- time2 = read_cntvct_el0();
+ time2 = virtualcounter_read();
}
+
+ return ((time2 - time1) * 1000) / timer_freq;
+}
+
+void sp_sleep(uint32_t ms)
+{
+ (void)sp_sleep_elapsed_time(ms);
}
diff --git a/spm/common/sp_helpers.h b/spm/common/sp_helpers.h
index 9f5400c..6fe8ec0 100644
--- a/spm/common/sp_helpers.h
+++ b/spm/common/sp_helpers.h
@@ -56,6 +56,9 @@
void announce_test_start(const char *test_desc);
void announce_test_end(const char *test_desc);
+/* Sleep for at least 'ms' milliseconds and return the elapsed time(ms). */
+uint64_t sp_sleep_elapsed_time(uint32_t ms);
+
/* Sleep for at least 'ms' milliseconds. */
void sp_sleep(uint32_t ms);