Date:   Mon, 31 Oct 2016 20:40:23 +1100 (AEDT)
From:   Finn Thain <fthain@...egraphics.com.au>
To:     Ondrej Zary <linux@...nbow-software.org>
cc:     Christoph Hellwig <hch@...radead.org>, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] NCR5380: Use probe_irq_*() for IRQ probing


On Mon, 31 Oct 2016, Ondrej Zary wrote:

> 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@...nbow-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?

I think so... but you're right, it is better if the delay remains here.

> 
> >
> > >  	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.

OK. I'm no expert on ISA so I'll leave it up to you.

-- 

> 
> >
> > > +	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.
> 
> 
> 
> 

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