linux-kernel - Re: [PATCH 1/3] ARM: imx: Add common imx cpuidle init functionality.

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Date:	Tue, 17 Apr 2012 09:43:01 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Robert Lee <rob.lee@...aro.org>
Cc:	kernel@...gutronix.de, linaro-dev@...ts.linaro.org,
	patches@...aro.org, daniel.lezcano@...aro.org,
	linux-kernel@...r.kernel.org, amit.kucheria@...aro.org,
	shawn.guo@...aro.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/3] ARM: imx: Add common imx cpuidle init functionality.

On Mon, Apr 16, 2012 at 06:50:12PM -0500, Robert Lee wrote:
> Add common cpuidle init functionality that can be used by various
> imx platforms.
> 
> Signed-off-by: Robert Lee <rob.lee@...aro.org>
> ---
> diff --git a/arch/arm/plat-mxc/Makefile b/arch/arm/plat-mxc/Makefile
> index e81290c..7c9e05f 100644
> --- a/arch/arm/plat-mxc/Makefile
> +++ b/arch/arm/plat-mxc/Makefile
> @@ -16,6 +16,8 @@ obj-$(CONFIG_MXC_ULPI) += ulpi.o
>  obj-$(CONFIG_MXC_USE_EPIT) += epit.o
>  obj-$(CONFIG_MXC_DEBUG_BOARD) += 3ds_debugboard.o
>  obj-$(CONFIG_CPU_FREQ_IMX)    += cpufreq.o
> +obj-$(CONFIG_CPU_IDLE)    += cpuidle.o
> +
>  ifdef CONFIG_SND_IMX_SOC
>  obj-y += ssi-fiq.o
>  obj-y += ssi-fiq-ksym.o
> diff --git a/arch/arm/plat-mxc/cpuidle.c b/arch/arm/plat-mxc/cpuidle.c
> new file mode 100644
> index 0000000..d1c9301
> --- /dev/null
> +++ b/arch/arm/plat-mxc/cpuidle.c
> @@ -0,0 +1,89 @@
> +/*
> + * Copyright 2012 Freescale Semiconductor, Inc.
> + * Copyright 2012 Linaro Ltd.
> + *
> + * The code contained herein is licensed under the GNU General Public
> + * License. You may obtain a copy of the GNU General Public License
> + * Version 2 or later at the following locations:
> + *
> + * http://www.opensource.org/licenses/gpl-license.html
> + * http://www.gnu.org/copyleft/gpl.html
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/io.h>
> +#include <linux/cpuidle.h>
> +#include <linux/hrtimer.h>
> +#include <linux/err.h>
> +#include <linux/slab.h>
> +
> +static struct cpuidle_device __percpu * imx_cpuidle_devices;
> +static struct cpuidle_driver *drv;
> +
> +void __init imx_cpuidle_set_driver(struct cpuidle_driver *p)
> +{
> +	drv = p;
> +}

You like it complicated, eh? Why do you introduce a function which sets
a variable...

> +
> +void imx_cpuidle_devices_uninit(void)
> +{
> +	int cpu_id;
> +	struct cpuidle_device *dev;
> +
> +	for_each_possible_cpu(cpu_id) {
> +		dev = per_cpu_ptr(imx_cpuidle_devices, cpu_id);
> +		cpuidle_unregister_device(dev);
> +	}
> +
> +	free_percpu(imx_cpuidle_devices);
> +}
> +
> +static int __init imx_cpuidle_init(void)

... instead of passing it directly to the function which uses it?

> +{
> +	struct cpuidle_device *dev;
> +	int cpu_id, ret;
> +
> +	if (!drv || drv->state_count > CPUIDLE_STATE_MAX) {
> +		pr_err("%s: Invalid Input\n", __func__);

You introduce a pointless error message on SoCs not setting a cpuidle
driver. When will people learn that initcalls do not only run on
machines they have on their desk?

> +		return -EINVAL;
> +	}
> +
> +	ret = cpuidle_register_driver(drv);
> +
> +	if (ret) {
> +		pr_err("%s: Failed to register cpuidle driver\n", __func__);

It's always nice to add the return value to the error message to get a
clue *what* went wrong. The function name though is rather
uninteresting.

Sascha


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