On 07/30, Arpit Goel wrote:
This patch ports PowerPC implementation of spin_event_timeout() for generic use. Architecture specific implementation can be added to asm/delay.h, which will override the generic linux implementation. Signed-off-by: Arpit Goel <B44344@xxxxxxxxxxxxx> ---
We use something similar internally but it's tied specifically to readl.
+#ifndef spin_event_timeout +/** + * spin_event_timeout - spin until a condition gets true or a timeout elapses + * @condition: a C expression to evalate + * @timeout: timeout, in microseconds + * @delay: the number of microseconds to delay between each evaluation of + * @condition + * + * The process spins until the condition evaluates to true (non-zero) or the + * timeout elapses. The return value of this macro is the value of + * @condition when the loop terminates. This allows you to determine the cause + * of the loop terminates. If the return value is zero, then you know a + * timeout has occurred. + * + * This primary purpose of this macro is to poll on a hardware register + * until a status bit changes. The timeout ensures that the loop still + * terminates even if the bit never changes. The delay is for devices that + * need a delay in between successive reads. + * + * gcc will optimize out the if-statement if @delay is a constant. + * + * This is copied from PowerPC based spin_event_timeout() implementation + * and modified for generic usecase. + */ +#define spin_event_timeout(condition, timeout, delay) \ +({ \ + typeof(condition) __ret; \ + unsigned long __loops = timeout/USECS_PER_JIFFY; \ + unsigned long __start = jiffies; \ + while (!(__ret = (condition)) && \ + time_before(jiffies, __start + __loops + 1)) \ + if (delay) \ + udelay(delay); \ + else \ + schedule(); \ + if (!__ret) \ + __ret = (condition); \ + __ret; \ +})
What do you do here if jiffies aren't incrementing (i.e interrupts are disabled). The time_before() check won't work there and it would be nice if we were able to use this in such situations. I think powerpc gets around this by reading the hardware timer directly? -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe linux-m68k" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html