linux-kernel - Re: [PATCH 1/6] irqchip: add the Alpine MSIX interrupt controller

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Date:	Mon, 8 Feb 2016 11:26:56 +0100
From:	Antoine Tenart <antoine.tenart@...e-electrons.com>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	Antoine Tenart <antoine.tenart@...e-electrons.com>,
	tglx@...utronix.de, jason@...edaemon.net, tsahee@...apurnalabs.com,
	rshitrit@...apurnalabs.com, thomas.petazzoni@...e-electrons.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] irqchip: add the Alpine MSIX interrupt controller

Hi Marc,

On Mon, Feb 08, 2016 at 09:44:49AM +0000, Marc Zyngier wrote:
> On 08/02/16 09:16, Antoine Tenart wrote:
> > +
> > +/* MSIX message address format: local GIC target */
> > +#define ALPINE_MSIX_SPI_TARGET_CLUSTER0		BIT(16)
> > +
> > +struct alpine_msix_data {
> > +	spinlock_t msi_map_lock;
> > +	u32 addr_high;
> > +	u32 addr_low;
> 
> As this looks to be a physical address, please consider using phys_addr_t.

Sure.

[…]

> > +static int alpine_msix_init(struct device_node *node,
> > +			    struct device_node *parent)
> > +{
> > +	struct alpine_msix_data *priv;
> > +	struct resource res;
> > +	int ret;
> > +
> > +	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
> > +	if (!priv)
> > +		return -ENOMEM;
> > +
> > +	spin_lock_init(&priv->msi_map_lock);
> > +
> > +	ret = of_address_to_resource(node, 0, &res);
> > +	if (ret) {
> > +		pr_err("Failed to allocate resource\n");
> > +		goto err_priv;
> > +	}
> > +
> > +	priv->addr_high = upper_32_bits((u64)res.start);
> > +	priv->addr_low = lower_32_bits(res.start) + ALPINE_MSIX_SPI_TARGET_CLUSTER0;
> 
> This is a bit odd. If you always set bit 16, why isn't that reflected in
> the base address coming from the DT?

The 20 least significant bits of addr_low provide direct information
regarding the interrupt destination, so I thought it would be clearer
to have this explicitly in the driver so that we know what those bits
mean.

What do you think?


Thanks for the review!

Antoine

-- 
Antoine Ténart, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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