Re: [PATCH 1/3] NCR5380: Use probe_irq_*() for IRQ probing

[Ondrej Zary <linux@rainbow-software.org>]

On Monday 31 October 2016, Finn Thain wrote:
> On Sun, 30 Oct 2016, Ondrej Zary wrote:
> > Use standard probe_irq_on() and probe_irq_off() functions instead of own
> > implementation.
>
> Thanks for doing this.
>
> > This prevents warning messages like this in the kernel log:
> > genirq: Flags mismatch irq 1. 00000000 (NCR-probe) vs. 00000080 (i8042)
> >
> > Move the IRQ trigger code to a separate function so it can be used for
> > other purposes (testing if the IRQ works).
> >
> > Also add missing IRQ reset after probe.
> >
> > Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
> > ---
> >  drivers/scsi/NCR5380.c   |   72
> > +++++++++++++++++----------------------------- drivers/scsi/NCR5380.h   |
> >    3 +-
> >  drivers/scsi/g_NCR5380.c |    2 +-
> >  3 files changed, 29 insertions(+), 48 deletions(-)
> >
> > diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c
> > index d849ffa..01c0027 100644
> > --- a/drivers/scsi/NCR5380.c
> > +++ b/drivers/scsi/NCR5380.c
> > @@ -351,50 +351,13 @@ static void NCR5380_print_phase(struct Scsi_Host
> > *instance) }
> >  #endif
> >
> > -
> > -static int probe_irq;
> > -
> > -/**
> > - * probe_intr	-	helper for IRQ autoprobe
> > - * @irq: interrupt number
> > - * @dev_id: unused
> > - * @regs: unused
> > - *
> > - * Set a flag to indicate the IRQ in question was received. This is
> > - * used by the IRQ probe code.
> > - */
> > -
> > -static irqreturn_t probe_intr(int irq, void *dev_id)
> > -{
> > -	probe_irq = irq;
> > -	return IRQ_HANDLED;
> > -}
> > -
> > -/**
> > - * NCR5380_probe_irq	-	find the IRQ of an NCR5380
> > - * @instance: NCR5380 controller
> > - * @possible: bitmask of ISA IRQ lines
> > - *
> > - * Autoprobe for the IRQ line used by the NCR5380 by triggering an IRQ
> > - * and then looking to see what interrupt actually turned up.
> > - */
> > -
> > -static int __maybe_unused NCR5380_probe_irq(struct Scsi_Host *instance,
> > -						int possible)
> > +static void NCR5380_trigger_irq(struct Scsi_Host *instance)
> >  {
> >  	struct NCR5380_hostdata *hostdata = shost_priv(instance);
> > -	unsigned long timeout;
> > -	int trying_irqs, i, mask;
> > -
> > -	for (trying_irqs = 0, i = 1, mask = 2; i < 16; ++i, mask <<= 1)
> > -		if ((mask & possible) && (request_irq(i, &probe_intr, 0, "NCR-probe",
> > NULL) == 0)) -			trying_irqs |= mask;
> > -
> > -	timeout = jiffies + msecs_to_jiffies(250);
> > -	probe_irq = NO_IRQ;
> > +	unsigned long timeout = jiffies + msecs_to_jiffies(2500);
> >
> >  	/*
> > -	 * A interrupt is triggered whenever BSY = false, SEL = true
> > +	 * An interrupt is triggered whenever BSY = false, SEL = true
> >  	 * and a bit set in the SELECT_ENABLE_REG is asserted on the
> >  	 * SCSI bus.
> >  	 *
> > @@ -402,23 +365,40 @@ static int __maybe_unused NCR5380_probe_irq(struct
> > Scsi_Host *instance, * (I/O, C/D, and MSG) match those in the TCR, so we
> > must reset that * to zero.
> >  	 */
> > -
> >  	NCR5380_write(TARGET_COMMAND_REG, 0);
> >  	NCR5380_write(SELECT_ENABLE_REG, hostdata->id_mask);
> >  	NCR5380_write(OUTPUT_DATA_REG, hostdata->id_mask);
> >  	NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE | ICR_ASSERT_DATA |
> > ICR_ASSERT_SEL);
> >
> > -	while (probe_irq == NO_IRQ && time_before(jiffies, timeout))
> > +	while (!(NCR5380_read(BUS_AND_STATUS_REG) & BASR_IRQ) &&
> > +	       time_before(jiffies, timeout))
> >  		schedule_timeout_uninterruptible(1);
>
> You don't need a 2.5 second timeout here. To raise the interrupt the chip
> should not need more than a bus settle delay (400ns). Calling msleep(1)
> should be plenty.

Yes, 2.5s is a mistake (leftover from testing), sorry.

> Better still, please drop the loop, the delay and the BASR_IRQ test here,
> and if need be, put the delay in the caller. This routine discards the
> result of that sequence anyway.

Will if work if the following lines are executed before the delay?

>
> >  	NCR5380_write(SELECT_ENABLE_REG, 0);
> >  	NCR5380_write(INITIATOR_COMMAND_REG, ICR_BASE);
> > +}
> >
> > -	for (i = 1, mask = 2; i < 16; ++i, mask <<= 1)
> > -		if (trying_irqs & mask)
> > -			free_irq(i, NULL);
> > +/**
> > + * NCR5380_probe_irq	-	find the IRQ of an NCR5380
> > + * @instance: NCR5380 controller
> > + *
> > + * Autoprobe for the IRQ line used by the NCR5380 by triggering an IRQ
> > + * and then looking to see what interrupt actually turned up.
> > + */
> > +
> > +static int NCR5380_probe_irq(struct Scsi_Host *instance)
> > +{
> > +	struct NCR5380_hostdata *hostdata = shost_priv(instance);
> > +	int irqs, irq;
> > +
>
> Please rename irqs to irq_mask.
>
> Other drivers like tty/cyclades.c begin with,
>
> 	/* forget possible initially masked and pending IRQ */
> 	irq = probe_irq_off(probe_irq_on());
>
> Perhaps we need that here too?

Only cyclades and 8250_port do that, other drivers don't.
Don't know what exact problem should that solve.

>
> > +	irqs = probe_irq_on();
>
> You should clear any pending interrupt on the chip before you try to
> trigger another one.
>
> > +	NCR5380_trigger_irq(instance);
>
> Please do the msleep(1) here.
>
> > +	irq = probe_irq_off(irqs);
> > +	NCR5380_read(RESET_PARITY_INTERRUPT_REG);
> > +	if (irq < 0)
> > +		irq = 0;
>
> Please use NO_IRQ instead of 0.
>
> > -	return probe_irq;
> > +	return irq;
> >  }
> >
> >  /**
> > diff --git a/drivers/scsi/NCR5380.h b/drivers/scsi/NCR5380.h
> > index 3c6ce54..b2fca52 100644
> > --- a/drivers/scsi/NCR5380.h
> > +++ b/drivers/scsi/NCR5380.h
> > @@ -290,7 +290,8 @@ static inline struct scsi_cmnd
> > *NCR5380_to_scmd(struct NCR5380_cmd *ncmd_ptr) #define
> > NCR5380_dprint_phase(flg, arg) do {} while (0)
> >  #endif
> >
> > -static int NCR5380_probe_irq(struct Scsi_Host *instance, int possible);
> > +static void NCR5380_trigger_irq(struct Scsi_Host *instance);
> > +static int NCR5380_probe_irq(struct Scsi_Host *instance);
> >  static int NCR5380_init(struct Scsi_Host *instance, int flags);
> >  static int NCR5380_maybe_reset_bus(struct Scsi_Host *);
> >  static void NCR5380_exit(struct Scsi_Host *instance);
>
> Please move NCR5380_probe_irq and NCR5380_trigger_irq implementations and
> prototypes out of the core driver and into g_NCR5380.c. The reason is, ISA
> cards are probably the only 5380 cards ever likely to need manual IRQ
> configuration. It would better to have g_NCR5380 support more ISA cards
> than to add more ISA drivers, therefore this code isn't likely to be
> needed in the core driver.
>
> Thanks.



-- 
Ondrej Zary