linux-kernel - Re: [PATCH V3 16/16] irqchip: crossbar: allow for quirky hardware with direct hardwiring of GIC

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Message-ID: <20140621025723.GF21711@titan.lakedaemon.net>
Date:	Fri, 20 Jun 2014 22:57:23 -0400
From:	Jason Cooper <jason@...edaemon.net>
To:	Sricharan R <r.sricharan@...com>
Cc:	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	tony@...mide.com, santosh.shilimkar@...com, nm@...com,
	rnayak@...com, linux@....linux.org.uk, tglx@...utronix.de,
	joe@...ches.com
Subject: Re: [PATCH V3 16/16] irqchip: crossbar: allow for quirky hardware
 with direct hardwiring of GIC

On Mon, Jun 16, 2014 at 04:53:16PM +0530, Sricharan R wrote:
> From: Nishanth Menon <nm@...com>
> 
> On certain platforms such as DRA7, SPIs 0, 1, 2, 3, 5, 6, 10, 131,
> 132, 133 are direct wired to hardware blocks bypassing crossbar.
> This quirky implementation is *NOT* supposed to be the expectation
> of crossbar hardware usage. However, these are already marked in our
> description of the hardware with SKIP and RESERVED where appropriate.
> 
> Unfortunately, we need to be able to refer to these hardwired IRQs.
> So, to request these, crossbar driver can use the existing information
> from it's table that these SKIP/RESERVED maps are direct wired sources
> and generic allocation/programming of crossbar should be avoided.
> 
> Signed-off-by: Nishanth Menon <nm@...com>
> Signed-off-by: Sricharan R <r.sricharan@...com>
> ---
>  .../devicetree/bindings/arm/omap/crossbar.txt      |   12 ++++++++++--
>  drivers/irqchip/irq-crossbar.c                     |   20 ++++++++++++++++++--
>  2 files changed, 28 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/arm/omap/crossbar.txt b/Documentation/devicetree/bindings/arm/omap/crossbar.txt
> index 8210ea4..438ccab 100644
> --- a/Documentation/devicetree/bindings/arm/omap/crossbar.txt
> +++ b/Documentation/devicetree/bindings/arm/omap/crossbar.txt
> @@ -42,8 +42,10 @@ Documentation/devicetree/bindings/arm/gic.txt for further details.
>  
>  An interrupt consumer on an SoC using crossbar will use:
>  	interrupts = <GIC_SPI request_number interrupt_level>
> -request number shall be between 0 to that described by
> -"ti,max-crossbar-sources"
> +When the request number is between 0 to that described by
> +"ti,max-crossbar-sources", it is assumed to be a crossbar mapping. If the
> +request_number is greater than "ti,max-crossbar-sources", then it is mapped as a
> +quirky hardware mapping direct to GIC.
>  
>  Example:
>  	device_x@...a023000 {
> @@ -51,3 +53,9 @@ Example:
>  		interrupts = <GIC_SPI 8 IRQ_TYPE_LEVEL_HIGH>;
>  		...
>  	};
> +
> +	device_y@...a033000 {
> +		/* Direct mapped GIC SPI 1 used */
> +		interrupts = <GIC_SPI 401 IRQ_TYPE_LEVEL_HIGH>;

Ideally, I'd like to see a macro here so that it's clear that we crossed
a magic threshold. eg:

#define MAX_SOURCES     400
#define DIRECT_IRQ(irq) (MAX_SOURCES + irq)
...
		interrupts = <GIC_SPI DIRECT_IRQ(1) IRQ_TYPE_LEVEL_HIGH>;

and, then:

		ti,max-crossbar-sources = <MAX_SOURCES>;

> +		...
> +	};
> diff --git a/drivers/irqchip/irq-crossbar.c b/drivers/irqchip/irq-crossbar.c
> index ef613c4..fff6218 100644
> --- a/drivers/irqchip/irq-crossbar.c
> +++ b/drivers/irqchip/irq-crossbar.c
> @@ -86,8 +86,13 @@ static inline int allocate_free_irq(int cb_no)
>  
>  static inline bool needs_crossbar_write(irq_hw_number_t hw)
>  {
> -	if (hw > GIC_IRQ_START)
> -		return true;
> +	int cb_no;
> +
> +	if (hw > GIC_IRQ_START) {
> +		cb_no = cb->irq_map[hw - GIC_IRQ_START];
> +		if (cb_no != IRQ_RESERVED && cb_no != IRQ_SKIP)
> +			return true;
> +	}
>  
>  	return false;
>  }
> @@ -130,8 +135,19 @@ static int crossbar_domain_xlate(struct irq_domain *d,
>  {
>  	int ret;
>  	int req_num = intspec[1];
> +	int direct_map_num;
>  
>  	if (req_num >= cb->max_crossbar_sources) {
> +		direct_map_num = req_num - cb->max_crossbar_sources;
> +		if (direct_map_num < cb->int_max) {
> +			ret = cb->irq_map[direct_map_num];
> +			if (ret == IRQ_RESERVED || ret == IRQ_SKIP) {
> +				/* We use the interrupt num as h/w irq num */
> +				ret = direct_map_num;
> +				goto found;
> +			}
> +		}
> +
>  		pr_err("%s: requested crossbar number %d > max %d\n",
>  		       __func__, req_num, cb->max_crossbar_sources);
>  		return -EINVAL;

thx,

Jason.
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