On 2020-06-17 10:27, Cornelia Huck wrote:
On Mon, 15 Jun 2020 11:31:55 +0200
Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:
The hardware gives us a good definition of the microsecond,
let's keep this information and let the routine accessing
the hardware keep all the information and return microseconds.
Calculate delays in microseconds and take care about wrapping
around zero.
Define values with macros and use inlines to keep the
milliseconds interface.
Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
lib/s390x/asm/time.h | 29 +++++++++++++++++++++++++++--
1 file changed, 27 insertions(+), 2 deletions(-)
diff --git a/lib/s390x/asm/time.h b/lib/s390x/asm/time.h
index 1791380..7f1d891 100644
--- a/lib/s390x/asm/time.h
+++ b/lib/s390x/asm/time.h
@@ -13,14 +13,39 @@
#ifndef ASM_S390X_TIME_H
#define ASM_S390X_TIME_H
-static inline uint64_t get_clock_ms(void)
+#define STCK_SHIFT_US (63 - 51)
+#define STCK_MAX ((1UL << 52) - 1)
+
+static inline uint64_t get_clock_us(void)
{
uint64_t clk;
asm volatile(" stck %0 " : : "Q"(clk) : "memory");
/* Bit 51 is incrememented each microsecond */
That comment may now be a tad non-obvious, because the details are
hidden behind the #define? Anyway, no strong opinion.
You are right.
I find the macro's name is explicit so I remove the comment.
- return (clk >> (63 - 51)) / 1000;
+ return clk >> STCK_SHIFT_US;
+}
+
+static inline void udelay(unsigned long us)
+{
+ unsigned long startclk = get_clock_us();
+ unsigned long c;
+
+ do {
+ c = get_clock_us();
+ if (c < startclk)
+ c += STCK_MAX;
+ } while (c < startclk + us);
+}
+
+static inline void mdelay(unsigned long ms)
+{
+ udelay(ms * 1000);
+}
+
+static inline uint64_t get_clock_ms(void)
+{
+ return get_clock_us() / 1000;
}
#endif
Acked-by: Cornelia Huck <cohuck@xxxxxxxxxx>
Thanks,
Pierre
--
Pierre Morel
IBM Lab Boeblingen
