From 5132570845443767539fc00b502f6eafbfa37ba2 Mon Sep 17 00:00:00 2001 From: Julius Werner Date: Fri, 2 Nov 2018 14:48:24 -0700 Subject: timer: Add wait_us/wait_ms helper macros to wait for conditions A very common pattern in drivers is that we need to wait for a condition to become true (e.g. for a lock bit in a PLL status register to become set), but we still want to have a maximum timeout before we treat it as an error. coreboot uses the stopwatch API for this, but it's still a little verbose for the most simple cases. This patch introduces two new helper macros that wrap this common application of the stopwatch API in a single line: wait_ms(XXX, YYY) waits for up to XXX milliseconds to see if the C condition 'if (YYY)' becomes true. The return value is 0 on failure (i.e. timeout expires without the condition becoming true) and the amount of elapsed time on success, so it can be used both in a boolean context and to log the amount of time waited. Replace the custom version used in an MTK ADC driver with this new generic version. Change-Id: I6de38ee00673c46332ae92b8a11099485de5327a Signed-off-by: Tristan Shieh Signed-off-by: Julius Werner Reviewed-on: https://review.coreboot.org/29315 Tested-by: build bot (Jenkins) Reviewed-by: Aaron Durbin --- src/include/timer.h | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) (limited to 'src/include') diff --git a/src/include/timer.h b/src/include/timer.h index 49eae5ec40..d3afb19646 100644 --- a/src/include/timer.h +++ b/src/include/timer.h @@ -15,6 +15,8 @@ #ifndef TIMER_H #define TIMER_H +#include + #define NSECS_PER_SEC 1000000000 #define USECS_PER_SEC 1000000 #define MSECS_PER_SEC 1000 @@ -195,4 +197,36 @@ static inline long stopwatch_duration_msecs(struct stopwatch *sw) return stopwatch_duration_usecs(sw) / USECS_PER_MSEC; } +/* + * Helper macro to wait until a condition becomes true or a timeout elapses. + * + * condition: a C expression to wait for + * timeout: timeout, in microseconds + * + * Returns: + * 0 if the condition still evaluates to false after the timeout elapsed, + * >0 if the condition evaluates to true. The return value is the amount of + * microseconds waited (at least 1). + */ +#define wait_us(timeout_us, condition) \ +({ \ + long __ret = 0; \ + struct stopwatch __sw; \ + stopwatch_init_usecs_expire(&__sw, timeout_us); \ + do { \ + if (condition) { \ + stopwatch_tick(&__sw); \ + __ret = stopwatch_duration_usecs(&__sw); \ + if (!__ret) /* make sure it evaluates to true */\ + __ret = 1; \ + break; \ + } \ + } while (!stopwatch_expired(&__sw)); \ + __ret; \ +}) + +#define wait_ms(timeout_ms, condition) \ + DIV_ROUND_UP(wait_us((timeout_ms) * USECS_PER_MSEC, condition), \ + USECS_PER_MSEC) + #endif /* TIMER_H */ -- cgit v1.2.3