[PATCH v3 6/6] arm: exynos: Add /dev/bL_status user interface on Exynos5420

[Abhilash Kesavan]

On Mon, Apr 28, 2014 at 4:55 PM, Daniel Lezcano
<daniel.lezcano at linaro.org> wrote:
> On 04/26/2014 06:05 PM, Abhilash Kesavan wrote:
>>
>> Add a user interface to check the core and cluster status on
>> Exynos5420. This can be utilized while debugging mcpm issues.
>> cat /dev/bL_status will show the current power status of all
>> the 8 cores along with the cluster.
>>
>> Signed-off-by: Thomas Abraham <thomas.ab at samsung.com>
>> Signed-off-by: Inderpal Singh <inderpal.s at samsung.com>
>> Signed-off-by: Andrew Bresticker <abrestic at chromium.org>
>> Signed-off-by: Abhilash Kesavan <a.kesavan at samsung.com>
>> ---
>
>
> Hi Abhilash,

Hi Daniel,
>
> I don't think you should add this file.
>
> 1. big Little is not exynos specific
But the core control/status bits that I am accessing are exynos
specific and currently it is being enabled only on 5420.
> 2. /dev is not for the purpose of your patch
OK.
>
> So I would recommend:
>
> 1. create a generic infra-structure for all the big.Little
> 2. and/or use debugfs
>
> Furthermore, how is it usable ? Will you read the file every 2ms to check
> the cluster status, knowing it will be woken up by the read operation ?
This was just a quick way to check the power status of the
cores/cluster during cpufreq controlled core switching. Maybe not as
useful in case of cpuidle.
>
> Frankly speaking, it would make sense to add traces in mcpm.c (if they
> aren't already there - did not check).
Fair enough, the core bL_switcher code does have code for trace
events. I can check more on that.

Regards,
Abhilash
>
>
>>   arch/arm/mach-exynos/mcpm-exynos.c | 64
>> ++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 64 insertions(+)
>>
>> diff --git a/arch/arm/mach-exynos/mcpm-exynos.c
>> b/arch/arm/mach-exynos/mcpm-exynos.c
>> index f9977bf..83428b0 100644
>> --- a/arch/arm/mach-exynos/mcpm-exynos.c
>> +++ b/arch/arm/mach-exynos/mcpm-exynos.c
>> @@ -269,6 +269,53 @@ static void __init exynos_mcpm_usage_count_init(void)
>>         cpu_use_count[cpu][cluster] = 1;
>>   }
>>
>> +static size_t bL_check_status(char *info)
>> +{
>> +       size_t len = 0;
>> +       int i;
>> +
>> +       len += sprintf(&info[len], "\t0 1 2 3 L2\n");
>> +       len += sprintf(&info[len], "[A15]   ");
>> +       for (i = 0; i < 4; i++) {
>> +               len += sprintf(&info[len], "%d ",
>> +                       (readl(EXYNOS_ARM_CORE_STATUS(i)) & 0x3) == 3 ? 1
>> : 0);
>> +       }
>> +       len += sprintf(&info[len], "%d\n",
>> +                       (readl(EXYNOS_COMMON_STATUS(0)) & 0x3) == 3 ? 1 :
>> 0);
>> +
>> +       len += sprintf(&info[len], "[A7]    ");
>> +       for (i = 4; i < 8; i++)
>> +               len += sprintf(&info[len], "%d ",
>> +                       (readl(EXYNOS_ARM_CORE_STATUS(i)) & 0x3) == 3 ? 1
>> : 0);
>> +       len += sprintf(&info[len], "%d\n\n",
>> +                       (readl(EXYNOS_COMMON_STATUS(1)) & 0x3) == 3 ? 1 :
>> 0);
>> +
>> +       return len;
>> +}
>> +
>> +static ssize_t bL_status_read(struct file *file, char __user *buf,
>> +                       size_t len, loff_t *pos)
>> +{
>> +       size_t count = 0;
>> +       char info[100];
>> +
>> +       count = bL_check_status(info);
>> +       if (count < 0)
>> +               return -EINVAL;
>> +
>> +       return simple_read_from_buffer(buf, len, pos, info, count);
>> +}
>> +
>> +static const struct file_operations bL_status_fops = {
>> +       .read           = bL_status_read,
>> +};
>> +
>> +static struct miscdevice bL_status_device = {
>> +       MISC_DYNAMIC_MINOR,
>> +       "bL_status",
>> +       &bL_status_fops
>> +};
>> +
>>   /*
>>    * Enable cluster-level coherency, in preparation for turning on the
>> MMU.
>>    */
>> @@ -319,3 +366,20 @@ static int __init exynos_mcpm_init(void)
>>   }
>>
>>   early_initcall(exynos_mcpm_init);
>> +
>> +static int __init exynos_bl_status_init(void)
>> +{
>> +       int ret;
>> +
>> +       if (!soc_is_exynos5420())
>> +               return -ENODEV;
>> +
>> +       ret = misc_register(&bL_status_device);
>> +       if (ret) {
>> +               pr_info("bl_status not available\n");
>> +               return ret;
>> +       }
>> +       return 0;
>> +}
>> +
>> +late_initcall(exynos_bl_status_init);
>>
>
>
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