78d81f2f84
When udelay() gets called with a delay that would expire before the next clock event it reprograms the clock comparator. When the interrupt happens the clock comparator won't be resetted therefore the interrupt condition doesn't get cleared. The result is an endless timer interrupt loop until the next clock event would expire (stored in lowcore). So udelay() usually would wait much longer for small delays than it should. Fix this by disabling the local tick which makes sure that the clock comparator will be resetted when a timer interrupt happens. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
117 lines
2.8 KiB
C
117 lines
2.8 KiB
C
/*
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* Precise Delay Loops for S390
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*
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* Copyright IBM Corp. 1999,2008
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* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
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* Heiko Carstens <heiko.carstens@de.ibm.com>,
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*/
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#include <linux/sched.h>
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#include <linux/delay.h>
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#include <linux/timex.h>
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#include <linux/module.h>
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#include <linux/irqflags.h>
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#include <linux/interrupt.h>
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void __delay(unsigned long loops)
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{
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/*
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* To end the bloody studid and useless discussion about the
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* BogoMips number I took the liberty to define the __delay
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* function in a way that that resulting BogoMips number will
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* yield the megahertz number of the cpu. The important function
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* is udelay and that is done using the tod clock. -- martin.
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*/
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asm volatile("0: brct %0,0b" : : "d" ((loops/2) + 1));
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}
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static void __udelay_disabled(unsigned long usecs)
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{
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unsigned long mask, cr0, cr0_saved;
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u64 clock_saved;
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clock_saved = local_tick_disable();
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set_clock_comparator(get_clock() + ((u64) usecs << 12));
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__ctl_store(cr0_saved, 0, 0);
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cr0 = (cr0_saved & 0xffff00e0) | 0x00000800;
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__ctl_load(cr0 , 0, 0);
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mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
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lockdep_off();
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trace_hardirqs_on();
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__load_psw_mask(mask);
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local_irq_disable();
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lockdep_on();
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__ctl_load(cr0_saved, 0, 0);
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local_tick_enable(clock_saved);
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set_clock_comparator(S390_lowcore.clock_comparator);
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}
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static void __udelay_enabled(unsigned long usecs)
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{
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unsigned long mask;
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u64 clock_saved;
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u64 end;
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mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT | PSW_MASK_IO;
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end = get_clock() + ((u64) usecs << 12);
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do {
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clock_saved = 0;
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if (end < S390_lowcore.clock_comparator) {
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clock_saved = local_tick_disable();
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set_clock_comparator(end);
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}
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trace_hardirqs_on();
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__load_psw_mask(mask);
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local_irq_disable();
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if (clock_saved)
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local_tick_enable(clock_saved);
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} while (get_clock() < end);
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set_clock_comparator(S390_lowcore.clock_comparator);
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}
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/*
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* Waits for 'usecs' microseconds using the TOD clock comparator.
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*/
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void __udelay(unsigned long usecs)
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{
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unsigned long flags;
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preempt_disable();
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local_irq_save(flags);
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if (in_irq()) {
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__udelay_disabled(usecs);
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goto out;
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}
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if (in_softirq()) {
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if (raw_irqs_disabled_flags(flags))
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__udelay_disabled(usecs);
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else
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__udelay_enabled(usecs);
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goto out;
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}
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if (raw_irqs_disabled_flags(flags)) {
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local_bh_disable();
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__udelay_disabled(usecs);
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_local_bh_enable();
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goto out;
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}
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__udelay_enabled(usecs);
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out:
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local_irq_restore(flags);
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preempt_enable();
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}
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EXPORT_SYMBOL(__udelay);
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/*
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* Simple udelay variant. To be used on startup and reboot
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* when the interrupt handler isn't working.
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*/
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void udelay_simple(unsigned long usecs)
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{
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u64 end;
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end = get_clock() + ((u64) usecs << 12);
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while (get_clock() < end)
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cpu_relax();
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}
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