Introduce timeout_init_us/timeout_elapsed() delay tracking with CNTPCT.

timeout_init_us(some_timeout_us); returns a reference to detect
timeout for the provided microsecond delay value from current time.

timeout_elapsed(reference) return true/false whether the reference
timeout is elapsed.

This change is inspired by the OP-TEE OS timeout resources [1].

 [1] https://github.com/OP-TEE/optee_os/blob/3.4.0/core/arch/arm/include/kernel/delay.h#L45



Change-Id: Id81ff48aa49693f555dc621064878417101d5587
Signed-off-by: Yann Gautier <yann.gautier@st.com>
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>

plat/st/common/include/stm32mp_common.h

 /*
  * Copyright (C) 2018-2019, STMicroelectronics - All Rights Reserved
+ * Copyright (c) 2018-2019, Linaro Limited
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -9,6 +10,8 @@
 
 #include <stdbool.h>
 
+#include <arch_helpers.h>
+
 /* Functions to save and get boot context address given by ROM code */
 void stm32mp_save_boot_ctx_address(uintptr_t address);
 uintptr_t stm32mp_get_boot_ctx_address(void);
@@ -42,4 +45,19 @@ unsigned long stm32mp_clk_get_rate(unsigned long id);
 /* Initialise the IO layer and register platform IO devices */
 void stm32mp_io_setup(void);
 
+static inline uint64_t arm_cnt_us2cnt(uint32_t us)
+{
+	return ((uint64_t)us * (uint64_t)read_cntfrq()) / 1000000ULL;
+}
+
+static inline uint64_t timeout_init_us(uint32_t us)
+{
+	return read_cntpct_el0() + arm_cnt_us2cnt(us);
+}
+
+static inline bool timeout_elapsed(uint64_t expire)
+{
+	return read_cntpct_el0() > expire;
+}
+
 #endif /* STM32MP_COMMON_H */