Hello,
In a real time module using the parallel port to measure interrupt
time difference, it seems that the ISR is called twice. I use a
signal generator at 1Hz to generate an interrupt at pin10, nAck of
the SPP. Using the code
unsigned int spp_isr( unsigned int irq_number, struct pt_regs *p )
{
DPRINTK( "Starting spp_isr\n" );
spp_byte = inb( RT_MCM_SPP_BASE+RT_MCM_SPP_STA );
spp_irqs++;
spp_irqs %= FRAME_LENGTH;
DPRINTK( "spp_irqs = %d\n", (int)(spp_irqs) );
spp_now = gethrtime();
spp_dT = (int)(spp_now - spp_past);
spp_past = spp_now;
if ( spp_dT < 0 )
spp_dT = spp_dT_past;
else
spp_dT_past = spp_dT;
DPRINTK( "spp_dT = %d\n", spp_dT );
rtl_hard_enable_irq( RT_MCM_SPP_IRQ );
DPRINTK( "Leaving spp_isr\n\n" );
return 0;
}
I get periodically at 1Hz with "cat /proc/kmsg":
<4>
<4>Starting rt_mcm_spp_isr
<4>rt_mcm_spp_irqs = 2
<4>rt_mcm_spp_dT = 1409260352
<4>Starting rt_mcm_spp_isr
<4>rt_mcm_spp_irqs = 3
<4>rt_mcm_spp_dT = 52064
<4>Leaving rt_mcm_spp_isr
<4>
<4>Leaving rt_mcm_spp_isr
<4>
Is it necessary to set something on the SPP in the ISR?
peterw
--
Dr. Peter Wurmsdobler
CTM - Centre de Transfert des Microtechniques
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