path: root/arch/s390/include/asm
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authorHeiko Carstens <hca@linux.ibm.com>2020-12-04 12:32:42 +0100
committerHeiko Carstens <hca@linux.ibm.com>2020-12-16 14:55:49 +0100
commitdd6cfe553212b6311cac27ecd2f67621857fb10a (patch)
tree75a5501adcd811dd9647cd7835d98fafdee32b8c /arch/s390/include/asm
parent91c2bad6aec98a51663ce9eec7c4825c1ca0b870 (diff)
s390/delay: simplify udelay
udelay is implemented by using quite subtle details to make it possible to load an idle psw and waiting for an interrupt even in irq context or when interrupts are disabled. Also handling (or better: no handling) of softirqs is taken into account. All this is done to optimize for something which should in normal circumstances never happen: calling udelay to busy wait. Therefore get rid of the whole complexity and just busy loop like other architectures are doing it also. It could have been possible to use diag 0x44 instead of cpu_relax() in the busy loop, however we have seen too many bad things happen with diag 0x44 that it seems to be better to simply busy loop. Also note that with this new implementation kernel preemption does work when within the udelay loop. This did not work before. To get a feeling what the former code optimizes for: IPL'ing a kernel with 'defconfig' and afterwards compiling a kernel ends with a total of zero udelay calls. Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Diffstat (limited to 'arch/s390/include/asm')
2 files changed, 6 insertions, 8 deletions
diff --git a/arch/s390/include/asm/delay.h b/arch/s390/include/asm/delay.h
index 4a08379cd1eb..b566be6f13f3 100644
--- a/arch/s390/include/asm/delay.h
+++ b/arch/s390/include/asm/delay.h
@@ -14,13 +14,13 @@
#define _S390_DELAY_H
void udelay_enable(void);
-void __ndelay(unsigned long long nsecs);
-void __udelay(unsigned long long usecs);
-void udelay_simple(unsigned long long usecs);
+void __ndelay(unsigned long nsecs);
+void __udelay(unsigned long usecs);
+void udelay_simple(unsigned long usecs);
void __delay(unsigned long loops);
-#define ndelay(n) __ndelay((unsigned long long) (n))
-#define udelay(n) __udelay((unsigned long long) (n))
-#define mdelay(n) __udelay((unsigned long long) (n) * 1000)
+#define ndelay(n) __ndelay((unsigned long)(n))
+#define udelay(n) __udelay((unsigned long)(n))
+#define mdelay(n) __udelay((unsigned long)(n) * 1000)
#endif /* defined(_S390_DELAY_H) */
diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 6b7269f51f83..85dfbb20467e 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -16,14 +16,12 @@
#define CIF_NOHZ_DELAY 2 /* delay HZ disable for a tick */
#define CIF_FPU 3 /* restore FPU registers */
-#define CIF_IGNORE_IRQ 4 /* ignore interrupt (for udelay) */
#define CIF_ENABLED_WAIT 5 /* in enabled wait state */
#define CIF_MCCK_GUEST 6 /* machine check happening in guest */
#define CIF_DEDICATED_CPU 7 /* this CPU is dedicated */

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