linux-kernel - Re: [PATCH v2,2/5] powerpc/rcpm: add RCPM driver

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Date:	Wed, 26 Aug 2015 15:35:39 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Chenhui Zhao <chenhui.zhao@...escale.com>
CC:	<linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
	<Jason.Jin@...escale.com>
Subject: Re: [PATCH v2,2/5] powerpc/rcpm: add RCPM driver

On Wed, Aug 26, 2015 at 08:09:45PM +0800, Chenhui Zhao wrote:
> +#ifdef CONFIG_PPC_BOOK3E
> +static void qoriq_disable_thread(int cpu)
> +{
> +	int hw_cpu = get_hard_smp_processor_id(cpu);
> +	int thread = cpu_thread_in_core(hw_cpu);
> +
> +	mtspr(SPRN_TENC, TEN_THREAD(thread));
> +}
> +#endif

This file is always used on book3e.  If the intent is to only build this
on 64-bit, use CONFIG_PPC64 rather than relying on the fact that this one
of the confusing mess of BOOKE/BOOK3E symbols is 64-bit-only.

> +static void rcpm_v2_cpu_die(int cpu)
> +{
> +#ifdef CONFIG_PPC_BOOK3E
> +	int primary;
> +
> +	if (threads_per_core == 2) {
> +		primary = cpu_first_thread_sibling(cpu);
> +		if (cpu_is_offline(primary) && cpu_is_offline(primary + 1)) {
> +			/* if both threads are offline, put the cpu in PH20 */
> +			rcpm_v2_cpu_enter_state(cpu, E500_PM_PH20);
> +		} else {
> +			/* if only one thread is offline, disable the thread */
> +			qoriq_disable_thread(cpu);
> +		}
> +	}
> +#endif
> +
> +	if (threads_per_core == 1) {
> +		rcpm_v2_cpu_enter_state(cpu, E500_PM_PH20);
> +		return;
> +	}
> +}

That "return;" adds nothing, and it's even more awkward having it on the
one-thread case but not the two-thread case.

> +static void rcpm_v1_cpu_up_prepare(int cpu)
> +{
> +	rcpm_v1_cpu_exit_state(cpu, E500_PM_PH15);
> +	rcpm_v1_irq_unmask(cpu);
> +}
> +
> +static void rcpm_v2_cpu_exit_state(int cpu, int state)
> +{
> +	int hw_cpu = get_hard_smp_processor_id(cpu);
> +	u32 mask = 1 << cpu_core_index_of_thread(hw_cpu);

Are you sure cpu_core_index_of_thread() is supposed to take a hardware
cpu id?  The only current user, pseries_energy.c, has the comment
"Convert logical cpu number to core number".

> +static const struct of_device_id rcpm_matches[] = {
> +	{
> +		.compatible = "fsl,qoriq-rcpm-1.0",
> +		.data = (void *)&qoriq_rcpm_v1_ops,
> +	},
> +	{
> +		.compatible = "fsl,qoriq-rcpm-2.0",
> +		.data = (void *)&qoriq_rcpm_v2_ops,
> +	},
> +	{
> +		.compatible = "fsl,qoriq-rcpm-2.1",
> +		.data = (void *)&qoriq_rcpm_v2_ops,
> +	},
> +	{},
> +};

Unnecessary (and const-unsafe) casts.

> +
> +int __init fsl_rcpm_init(void)
> +{
> +	struct device_node *np;
> +	const struct of_device_id *match;
> +	void __iomem *base;
> +
> +	np = of_find_matching_node_and_match(NULL, rcpm_matches, &match);
> +	if (!np) {
> +		pr_err("can't find the rcpm node.\n");
> +		return -ENODEV;
> +	}

It's not an error for the device tree node to not have this.

-Scott
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