linux-kernel - Re: [PATCH] irqchip: bcm2835: Add FIQ support

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Message-ID: <87d1zj6fq2.fsf@eliezer.anholt.net>
Date:	Wed, 22 Jul 2015 14:32:21 -0700
From:	Eric Anholt <eric@...olt.net>
To:	Noralf Trønnes <noralf@...nnes.org>,
	tglx@...utronix.de, jason@...edaemon.net
Cc:	linux-rpi-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Noralf Trønnes <noralf@...nnes.org>
Subject: Re: [PATCH] irqchip: bcm2835: Add FIQ support

Noralf Trønnes <noralf@...nnes.org> writes:

> Add a duplicate irq range with an offset on the hwirq's so the
> driver can detect that enable_fiq() is used.
> Tested with downstream dwc_otg USB controller driver.
>
> Signed-off-by: Noralf Trønnes <noralf@...nnes.org>
> ---
>  arch/arm/mach-bcm/Kconfig     |  1 +
>  drivers/irqchip/irq-bcm2835.c | 53 ++++++++++++++++++++++++++++++++++++++-----
>  2 files changed, 48 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm/mach-bcm/Kconfig b/arch/arm/mach-bcm/Kconfig
> index 8b11f44..7cfef7b 100644
> --- a/arch/arm/mach-bcm/Kconfig
> +++ b/arch/arm/mach-bcm/Kconfig
> @@ -114,6 +114,7 @@ config ARCH_BCM2835
>  	select ARM_ERRATA_411920
>  	select ARM_TIMER_SP804
>  	select CLKSRC_OF
> +	select FIQ
>  	select PINCTRL
>  	select PINCTRL_BCM2835
>  	help
> diff --git a/drivers/irqchip/irq-bcm2835.c b/drivers/irqchip/irq-bcm2835.c
> index 5916d6c..db66246 100644
> --- a/drivers/irqchip/irq-bcm2835.c
> +++ b/drivers/irqchip/irq-bcm2835.c
> @@ -56,7 +56,7 @@
>  #include "irqchip.h"
>  
>  /* Put the bank and irq (32 bits) into the hwirq */
> -#define MAKE_HWIRQ(b, n)	((b << 5) | (n))
> +#define MAKE_HWIRQ(b, n)	(((b) << 5) | (n))
>  #define HWIRQ_BANK(i)		(i >> 5)
>  #define HWIRQ_BIT(i)		BIT(i & 0x1f)
>  
> @@ -72,9 +72,13 @@
>  					| SHORTCUT1_MASK | SHORTCUT2_MASK)
>  
>  #define REG_FIQ_CONTROL		0x0c
> +#define REG_FIQ_ENABLE		0x80
> +#define REG_FIQ_DISABLE		0
>  
>  #define NR_BANKS		3
>  #define IRQS_PER_BANK		32
> +#define NUMBER_IRQS		MAKE_HWIRQ(NR_BANKS, 0)
> +#define FIQ_START		(NR_IRQS_BANK0 + MAKE_HWIRQ(NR_BANKS - 1, 0))
>  
>  static int reg_pending[] __initconst = { 0x00, 0x04, 0x08 };
>  static int reg_enable[] __initconst = { 0x18, 0x10, 0x14 };
> @@ -98,14 +102,38 @@ static struct armctrl_ic intc __read_mostly;
>  static void __exception_irq_entry bcm2835_handle_irq(
>  	struct pt_regs *regs);
>  
> +static inline unsigned int hwirq_to_fiq(unsigned long hwirq)
> +{
> +	hwirq -= NUMBER_IRQS;
> +	/*
> +	 * The hwirq numbering used in this driver is:
> +	 *   BASE (0-7) GPU1 (32-63) GPU2 (64-95).
> +	 * This differ from the one used in the FIQ register:
> +	 *   GPU1 (0-31) GPU2 (32-63) BASE (64-71)
> +	 */
> +	if (hwirq >= 32)
> +		return hwirq - 32;
> +
> +	return hwirq + 64;
> +}
> +
>  static void armctrl_mask_irq(struct irq_data *d)
>  {
> -	writel_relaxed(HWIRQ_BIT(d->hwirq), intc.disable[HWIRQ_BANK(d->hwirq)]);
> +	if (d->hwirq >= NUMBER_IRQS)
> +		writel_relaxed(REG_FIQ_DISABLE, intc.base + REG_FIQ_CONTROL);
> +	else
> +		writel_relaxed(HWIRQ_BIT(d->hwirq),
> +			       intc.disable[HWIRQ_BANK(d->hwirq)]);
>  }
>  
>  static void armctrl_unmask_irq(struct irq_data *d)
>  {
> -	writel_relaxed(HWIRQ_BIT(d->hwirq), intc.enable[HWIRQ_BANK(d->hwirq)]);
> +	if (d->hwirq >= NUMBER_IRQS)
> +		writel_relaxed(REG_FIQ_ENABLE | hwirq_to_fiq(d->hwirq),
> +			       intc.base + REG_FIQ_CONTROL);
> +	else
> +		writel_relaxed(HWIRQ_BIT(d->hwirq),
> +			       intc.enable[HWIRQ_BANK(d->hwirq)]);
>  }

I found it nice for the 2836 controller to declare a new irqchip when
both the mask/unmask hooks needed to be changed for that class of
interrupt.  However, it looks like these functions aren't going to be
called regularly, so it doesn't matter much.

As far as interaction with my 2836 series, it looks like the only thing
downstream does is make the FIQ get handled on CPU1 instead of CPU0.  I
think we'll be fine fixing this up later.

Reviewed-by: Eric Anholt <eric@...olt.net>

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