Re: [PATCH 01/18] irqchip: vf610-gpc: add Vybrid GPC IRQ controller

[Marc Zyngier]

On Fri, 11 Mar 2016 10:11:43 -0800
Stefan Agner <stefan@xxxxxxxx> wrote:

> Hi Marc,
> 
> On 2016-03-10 19:41, Marc Zyngier wrote:
> > On Wed,  9 Mar 2016 18:16:42 -0800
> > Stefan Agner <stefan@xxxxxxxx> wrote:
> > 
> > Hi Stefan,
> > 
> >> This patch introduces a driver for Vybrids GPC (Global Power
> >> Controller). Vybrids GPC IP is simpler than the one found in
> >> i.MX 6: There is no power gating control (GPC) and the GPC INTC
> >> does not need to clear IRQ masks for an interrupt to get routed
> >> to the GIC (the mask only applys for wake-up control).
> >>
> >> Signed-off-by: Stefan Agner <stefan@xxxxxxxx>
> >> ---
> >>  drivers/irqchip/Makefile        |   1 +
> >>  drivers/irqchip/irq-vf610-gpc.c | 138 ++++++++++++++++++++++++++++++++++++++++
> >>  2 files changed, 139 insertions(+)
> >>  create mode 100644 drivers/irqchip/irq-vf610-gpc.c
> >>
> >> diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
> >> index 18caacb..0a77ac6 100644
> >> --- a/drivers/irqchip/Makefile
> >> +++ b/drivers/irqchip/Makefile
> >> @@ -45,6 +45,7 @@ obj-$(CONFIG_TS4800_IRQ)		+= irq-ts4800.o
> >>  obj-$(CONFIG_XTENSA)			+= irq-xtensa-pic.o
> >>  obj-$(CONFIG_XTENSA_MX)			+= irq-xtensa-mx.o
> >>  obj-$(CONFIG_IRQ_CROSSBAR)		+= irq-crossbar.o
> >> +obj-$(CONFIG_SOC_VF610)			+= irq-vf610-gpc.o
> >>  obj-$(CONFIG_SOC_VF610)			+= irq-vf610-mscm-ir.o
> >>  obj-$(CONFIG_BCM7038_L1_IRQ)		+= irq-bcm7038-l1.o
> >>  obj-$(CONFIG_BCM7120_L2_IRQ)		+= irq-bcm7120-l2.o
> >> diff --git a/drivers/irqchip/irq-vf610-gpc.c b/drivers/irqchip/irq-vf610-gpc.c
> >> new file mode 100644
> >> index 0000000..2c6a043
> >> --- /dev/null
> >> +++ b/drivers/irqchip/irq-vf610-gpc.c
> >> @@ -0,0 +1,138 @@
> >> +/*
> >> + * Copyright (C) 2016 Toradex AG
> >> + * Author: Stefan Agner <stefan@xxxxxxxx>
> >> + *
> >> + * This program is free software; you can redistribute it and/or modify
> >> + * it under the terms of the GNU General Public License version 2 as
> >> + * published by the Free Software Foundation.
> >> + *
> >> + *
> >> + * The GPC (General Power Controller) irqchip driver takes care of the
> >> + * interrupt wakeup functionality.
> >> + *
> >> + * o All peripheral interrupts of the Vybrid SoC can be used as wakeup
> >> + *   source from STOP mode. In LPSTOP mode however, the GPC is unpowered
> >> + *   too and cannot be used to as a wakeup source. The WKPU (Wakeup Unit)
> >> + *   is responsible for wakeups from LPSTOP modes.
> >> + */
> >> +
> >> +#include <linux/cpu_pm.h>
> >> +#include <linux/io.h>
> >> +#include <linux/irq.h>
> >> +#include <linux/irqchip.h>
> >> +#include <linux/irqdomain.h>
> >> +#include <linux/mfd/syscon.h>
> >> +#include <dt-bindings/interrupt-controller/arm-gic.h>
> >> +#include <linux/of.h>
> >> +#include <linux/of_address.h>
> >> +#include <linux/slab.h>
> >> +#include <linux/regmap.h>
> >> +
> >> +#define IMR_NUM			4
> >> +#define VF610_GPC_IMR1		0x044
> >> +#define VF610_GPC_MAX_IRQS	(IMR_NUM * 32)
> >> +
> >> +static void __iomem *gpc_base;
> >> +
> >> +static int vf610_gpc_irq_set_wake(struct irq_data *d, unsigned int on)
> >> +{
> >> +	unsigned int idx = d->hwirq / 32;
> >> +	void __iomem *reg_imr = gpc_base + VF610_GPC_IMR1 + (idx * 4);
> >> +	u32 mask = 1 << d->hwirq % 32;
> >> +
> >> +	if (on)
> >> +		writel_relaxed(readl_relaxed(reg_imr) & ~mask, reg_imr);
> >> +	else
> >> +		writel_relaxed(readl_relaxed(reg_imr) | mask, reg_imr);
> >> +
> >> +	/*
> >> +	 * Do *not* call into the parent, as the GIC doesn't have any
> >> +	 * wake-up facility...
> >> +	 */
> >> +	return 0;
> >> +}
> >> +
> >> +static struct irq_chip vf610_gpc_chip = {
> >> +	.name			= "vf610-gpc",
> >> +	.irq_mask		= irq_chip_mask_parent,
> >> +	.irq_unmask		= irq_chip_unmask_parent,
> >> +	.irq_enable		= irq_chip_enable_parent,
> >> +	.irq_disable		= irq_chip_disable_parent,
> > 
> > Any reason why you are providing enable/disable methods? This driver
> > seems to be GIC specific (various comments in the code), but the GIC
> > doesn't implement those.
> 
> There is another IRQ controller between the CPU's IRQ controller and the
> peripherals: the MSCM Interrupt Router
> (drivers/irqchip/irq-vf610-mscm-ir.c).
> 
> This router allows to select to which CPU an interrupt gets routed
> (VF6xx variants of Vybrid with a Cortex-A5 and Cortex-M4 core).
> 
> > 
> >> +	.irq_eoi		= irq_chip_eoi_parent,
> >> +	.irq_retrigger		= irq_chip_retrigger_hierarchy,
> >> +	.irq_set_wake		= vf610_gpc_irq_set_wake,
> >> +};
> >> +
> >> +static int vf610_gpc_domain_alloc(struct irq_domain *domain, unsigned int virq,
> >> +				  unsigned int nr_irqs, void *arg)
> >> +{
> >> +	int i;
> >> +	irq_hw_number_t hwirq;
> >> +	struct irq_fwspec *fwspec = arg;
> >> +	struct irq_fwspec parent_fwspec;
> >> +
> >> +	if (!irq_domain_get_of_node(domain->parent))
> >> +		return -EINVAL;
> >> +
> >> +	if (fwspec->param_count != 2)
> >> +		return -EINVAL;
> >> +
> >> +	hwirq = fwspec->param[0];
> >> +	for (i = 0; i < nr_irqs; i++)
> >> +		irq_domain_set_hwirq_and_chip(domain, virq + i, hwirq + i,
> >> +					      &vf610_gpc_chip, NULL);
> >> +
> >> +	parent_fwspec = *fwspec;
> > 
> > Now I'm confused. The next irqchip in the hierarchy cannot be the GIC,
> > because that's the wrong fwspec format (the GIC expect 3 parameters).
> > Glancing at patch #2, I can see that this points to the mscm, so maybe
> > it is that the comments are just wrong?
> 
> The above should explain that...
> 
> So with this driver the domain hierarchy stacks 3 IRQ controllers
> 
> GPC -> MSCM-IR -> NVIC/GIC (depending on CPU)
> 

In which case, can you drop the references to the GIC in the various
comments (in the commit message and in the set_wake function)? This
irqchip never "see" the GIC directly, and the MSCM-IR always acts as an
"impedance matcher".

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny.