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    SubjectRe: [PATCH 1/3] ARM: imx: Add common imx cpuidle init functionality.
    On Tue, Apr 17, 2012 at 2:43 AM, Sascha Hauer <s.hauer@pengutronix.de> wrote:
    > 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@linaro.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...
    >

    This complication is used to deal with the timing of various levels of
    init calls. More explanation below.

    >> +
    >> +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?
    >

    If I called imx_cpuidle_init directly from imx5 or imx6q init
    routines, it would be getting called before the coreinit_call of core
    cpuidle causing a failure. There were various other directions to
    take and all seemed less desirable than this one.

    One alternative would be to add a function to return the pointer to
    the cpuidle driver object based on the machine type. Functionality
    exists to identify imx5 as a machine type but not imx6q, so I couldn't
    use that machine based method without adding that extra code.

    Another alternative would be to add a general platform lateinit_call
    function to each platforms that support cpuidle.

    >> +{
    >> +     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?
    >

    Will fix in next version.

    >> +             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.

    Will add the return value in the next version.

    >
    > Sascha
    >
    >
    > --
    > Pengutronix e.K.                           |                             |
    > Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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