Date:	Thu, 14 Nov 2013 14:12:25 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	Sricharan R <r.sricharan@...com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linus.walleij@...aro.org" <linus.walleij@...aro.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"tony@...mide.com" <tony@...mide.com>,
	"rnayak@...com" <rnayak@...com>,
	Marc Zyngier <Marc.Zyngier@....com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"robherring2@...il.com" <robherring2@...il.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"nm@...com" <nm@...com>,
	"bcousson@...libre.com" <bcousson@...libre.com>
Subject: Re: [PATCH V4 2/4] DRIVERS: IRQCHIP: CROSSBAR: Add support for
 Crossbar IP

On Thu, Nov 14, 2013 at 12:18:48PM +0000, Sricharan R wrote:
> Some socs have a large number of interrupts requests to service
> the needs of its many peripherals and subsystems. All of the
> interrupt lines from the subsystems are not needed at the same
> time, so they have to be muxed to the irq-controller appropriately.
> In such places a interrupt controllers are preceded by an CROSSBAR
> that provides flexibility in muxing the device requests to the controller
> inputs.
> 
> This driver takes care a allocating a free irq and then configuring the
> crossbar IP as a part of the mpu's irqchip callbacks. crossbar_init should
> be called right before the irqchip_init, so that it is setup to handle the
> irqchip callbacks.
> 
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Linus Walleij <linus.walleij@...aro.org>
> Cc: Santosh Shilimkar <santosh.shilimkar@...com>
> Cc: Russell King <linux@....linux.org.uk>
> Cc: Tony Lindgren <tony@...mide.com>
> Cc: Rajendra Nayak <rnayak@...com>
> Cc: Marc Zyngier <marc.zyngier@....com>
> Cc: Grant Likely <grant.likely@...aro.org>
> Cc: Rob Herring <rob.herring@...xeda.com>
> Signed-off-by: Sricharan R <r.sricharan@...com>
> Acked-by: Kumar Gala <galak@...eaurora.org> (for DT binding portion)
> Acked-by: Santosh Shilimkar <santosh.shilimkar@...com>
> ---
>  [V2] Addressed Thomas Gleixner <tglx@...utronix.de> comments
>       and renamed the bindings as per Kumar Gala <galak@...eaurora.org>
>       comments.
>  [V3] Changed static inline const to static inline int and removed
>       unnecessary variable initialization as per
>       Thomas Gleixner <tglx@...utronix.de>. Updated commit tags
>  [V4] Renamed crossbar_init as irqcrossbar_init as per
>       Rajendra Nayak <rnayak@...com> suggestion.
> 
>  .../devicetree/bindings/arm/omap/crossbar.txt      |   27 +++
>  drivers/irqchip/Kconfig                            |    8 +
>  drivers/irqchip/Makefile                           |    1 +
>  drivers/irqchip/irq-crossbar.c                     |  206 ++++++++++++++++++++
>  include/linux/irqchip/irq-crossbar.h               |   11 ++
>  5 files changed, 253 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/omap/crossbar.txt
>  create mode 100644 drivers/irqchip/irq-crossbar.c
>  create mode 100644 include/linux/irqchip/irq-crossbar.h
> 
> diff --git a/Documentation/devicetree/bindings/arm/omap/crossbar.txt b/Documentation/devicetree/bindings/arm/omap/crossbar.txt
> new file mode 100644
> index 0000000..fb88585
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/omap/crossbar.txt
> @@ -0,0 +1,27 @@
> +Some socs have a large number of interrupts requests to service
> +the needs of its many peripherals and subsystems. All of the
> +interrupt lines from the subsystems are not needed at the same
> +time, so they have to be muxed to the irq-controller appropriately.
> +In such places a interrupt controllers are preceded by an CROSSBAR
> +that provides flexibility in muxing the device requests to the controller
> +inputs.
> +
> +Required properties:
> +- compatible : Should be "ti,irq-crossbar"
> +- reg: Base address and the size of the crossbar registers.
> +- ti,max-irqs: Total number of irqs available at the interrupt controller.
> +- ti,reg-size: Size of a individual register in bytes. Every individual
> +	    register is assumed to be of same size. Valid sizes are 1, 2, 4.
> +- ti,irqs-reserved: List of the reserved irq lines that are not muxed using
> +		 crossbar. These interrupt lines are reserved in the soc,
> +		 so crossbar bar driver should not consider them as free
> +		 lines.

The combination of the ti,max-irqs and ti,irqs-reserved properties seems
backwards to me. Why can we not describe the set of IRQs that _can_ be
used?

> +
> +Examples:
> +		crossbar_mpu: @4a020000 {
> +			compatible = "ti,irq-crossbar";
> +			reg = <0x4a002a48 0x130>;
> +			ti,max-irqs = <160>;
> +			ti,reg-size = <2>;
> +			ti,irqs-reserved = <0 1 2 3 5 6 131 132 139 140>;
> +		};

[...]

> +	/* Get and mark reserved irqs */
> +	irqsr = of_get_property(node, "ti,irqs-reserved", &size);
> +	if (irqsr) {
> +		size /= sizeof(__be32);
> +
> +		for (i = 0; i < size; i++) {
> +			entry = be32_to_cpup(irqsr + i);
> +			if (entry > max) {
> +				pr_err("Invalid reserved entry\n");
> +				goto err3;
> +			}
> +			cb->irq_map[entry] = 0;
> +		}
> +	}

Don't deal with the raw DTB. Use of_property_read_u32_index.

> +
> +	cb->register_offsets = kzalloc(max * sizeof(int), GFP_KERNEL);
> +	if (!cb->register_offsets)
> +		goto err3;
> +
> +	of_property_read_u32(node, "ti,reg-size", &size);

If "ti,reg-size" isn't present, size is uninitialized. Please check the
return value of of_property_read_u32.

Thanks,
Mark.
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