linux-kernel - Re: [PATCH RFC 04/10] base: power: Add generic OF-based power domain look-up

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Message-ID: <20140123001802.GF13785@codeaurora.org>
Date:	Wed, 22 Jan 2014 16:18:02 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Tomasz Figa <tomasz.figa@...il.com>
Cc:	linux-pm@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
	devicetree@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
	Russell King <linux@....linux.org.uk>,
	Pawel Moll <pawel.moll@....com>,
	Len Brown <len.brown@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Tomasz Figa <t.figa@...sung.com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Pavel Machek <pavel@....cz>, Kumar Gala <galak@...eaurora.org>,
	Stephen Warren <swarren@...dotorg.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH RFC 04/10] base: power: Add generic OF-based power
 domain look-up

On 01/11, Tomasz Figa wrote:
> +
> +/**
> + * of_genpd_lock() - Lock access to of_genpd_providers list
> + */
> +static void of_genpd_lock(void)
> +{
> +	mutex_lock(&of_genpd_mutex);
> +}
> +
> +/**
> + * of_genpd_unlock() - Unlock access to of_genpd_providers list
> + */
> +static void of_genpd_unlock(void)
> +{
> +	mutex_unlock(&of_genpd_mutex);
> +}

Why do we need these functions? Can't we just call
mutex_lock/unlock directly?

> +
> +/**
> + * of_genpd_add_provider() - Register a domain provider for a node
> + * @np: Device node pointer associated with domain provider
> + * @genpd_src_get: callback for decoding domain
> + * @data: context pointer for @genpd_src_get callback.

These look a little outdated.

> + */
> +int of_genpd_add_provider(struct device_node *np, genpd_xlate_t xlate,
> +			  void *data)
> +{
> +	struct of_genpd_provider *cp;
> +
> +	cp = kzalloc(sizeof(struct of_genpd_provider), GFP_KERNEL);

Please use sizeof(*cp) instead.

> +	if (!cp)
> +		return -ENOMEM;
> +
> +	cp->node = of_node_get(np);
> +	cp->data = data;
> +	cp->xlate = xlate;
> +
> +	of_genpd_lock();
> +	list_add(&cp->link, &of_genpd_providers);
> +	of_genpd_unlock();
> +	pr_debug("Added domain provider from %s\n", np->full_name);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(of_genpd_add_provider);
> +
[...]
> +
> +/* See of_genpd_get_from_provider(). */
> +static struct generic_pm_domain *__of_genpd_get_from_provider(
> +					struct of_phandle_args *genpdspec)
> +{
> +	struct of_genpd_provider *provider;
> +	struct generic_pm_domain *genpd = ERR_PTR(-ENOENT);

Can this be -EPROBE_DEFER so that we can defer probe until a
later time if the power domain provider hasn't registered yet?

> +
> +	/* Check if we have such a provider in our array */
> +	list_for_each_entry(provider, &of_genpd_providers, link) {
> +		if (provider->node == genpdspec->np)
> +			genpd = provider->xlate(genpdspec, provider->data);
> +		if (!IS_ERR(genpd))
> +			break;
> +	}
> +
> +	return genpd;
> +}
> +
[...]
> +static int of_genpd_notifier_call(struct notifier_block *nb,
> +				  unsigned long event, void *data)
> +{
> +	struct device *dev = data;
> +	int ret;
> +
> +	if (!dev->of_node)
> +		return NOTIFY_DONE;
> +
> +	switch (event) {
> +	case BUS_NOTIFY_BIND_DRIVER:
> +		ret = of_genpd_add_to_domain(dev);
> +		break;
> +
> +	case BUS_NOTIFY_UNBOUND_DRIVER:
> +		ret = of_genpd_del_from_domain(dev);
> +		break;
> +
> +	default:
> +		return NOTIFY_DONE;
> +	}
> +
> +	return notifier_from_errno(ret);
> +}
> +
> +static struct notifier_block of_genpd_notifier_block = {
> +	.notifier_call = of_genpd_notifier_call,
> +};
> +
> +static int of_genpd_init(void)
> +{
> +	return bus_register_notifier(&platform_bus_type,
> +					&of_genpd_notifier_block);
> +}
> +core_initcall(of_genpd_init);

Would it be possible to call the of_genpd_add_to_domain() and
of_genpd_del_from_domain() functions directly in the driver core,
similar to how the pinctrl framework has a hook in there? That
way we're not relying on any initcall ordering for this.

-- 
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