Re: [PATCH] irqchip: bcm2835: Add FIQ support

Russell King - ARM Linux
2015-09-14T09:09:15Z

On Sun, Sep 13, 2015 at 09:24:48PM +0200, Noralf Trønnes wrote:
>
> Den 22.07.2015 23:32, skrev Eric Anholt:
> >Noralf Trønnes <noralf@tronnes.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@tronnes.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@anholt.net>
>
> It seems that this has slipped through the cracks, at least it didn't
> enter in the 4.3 merge window.

... to which I'm glad.

What's the use-case for FIQs on this SMP platform? Where's the code that
makes use of the provided FIQs?

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