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

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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@xxxxxxxxxxxxxxxxxxxx>
> ---
>  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.

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.

>  
>  	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?

> +	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.

-- 

> diff --git a/drivers/scsi/g_NCR5380.c b/drivers/scsi/g_NCR5380.c
> index 7299ad9..3790ed5 100644
> --- a/drivers/scsi/g_NCR5380.c
> +++ b/drivers/scsi/g_NCR5380.c
> @@ -265,7 +265,7 @@ static int generic_NCR5380_init_one(struct scsi_host_template *tpnt,
>  	if (irq != IRQ_AUTO)
>  		instance->irq = irq;
>  	else
> -		instance->irq = NCR5380_probe_irq(instance, 0xffff);
> +		instance->irq = NCR5380_probe_irq(instance);
>  
>  	/* Compatibility with documented NCR5380 kernel parameters */
>  	if (instance->irq == 255)
> 

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