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

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Message-ID: <56B86EA8.9070306@arm.com>
Date:	Mon, 8 Feb 2016 10:32:08 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Antoine Tenart <antoine.tenart@...e-electrons.com>
Cc:	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

On 08/02/16 10:26, Antoine Tenart wrote:
>>> +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.

So what is this information? TARGET_CLUSTER0 is not very expressive, and
doesn't show what the alternatives are. Could you please elaborate a bit
on that front?

Thanks,

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