Re: [PATCH v13 1/2] leds: core: Introduce LED pattern trigger
From: Baolin Wang
Date: Mon Oct 01 2018 - 09:19:02 EST
Hi Jacek,
On 30 September 2018 at 23:33, Jacek Anaszewski
<jacek.anaszewski@xxxxxxxxx> wrote:
> Hi Baolin,
>
> Thank you for adding the dimming support.
>
> I've tested it and detected severe problem when
> delta_t is lower than 50, i.e. UPDATE_INTERVAL.
>
> echo "10 49 20 49" > pattern
>
> results after a while in a system wide freeze, see the following
> kernel log:
>
> [ 210.593592] rcu: INFO: rcu_sched self-detected stall on CPU
> [ 210.593601] rcu: 4-....: (21134 ticks this GP) idle=5b6/0/0x3
> softirq=4843/4843 fqs=5250
> [ 210.593602] rcu: (t=21000 jiffies g=25697 q=79)
> [ 210.593605] NMI backtrace for cpu 4
> [ 210.593608] CPU: 4 PID: 0 Comm: swapper/4 Not tainted 4.19.0-rc1+ #156
> [ 210.593609] Hardware name: Gigabyte Technology Co., Ltd.
> Z97-HD3/Z97-HD3, BIOS F6 06/11/2014
> [ 210.593609] Call Trace:
> [ 210.593612] <IRQ>
> [ 210.593618] dump_stack+0x46/0x5b
> [ 210.593621] nmi_cpu_backtrace+0x90/0xa0
> [ 210.593625] ? lapic_can_unplug_cpu+0x90/0x90
> [ 210.593627] nmi_trigger_cpumask_backtrace+0x8d/0xc0
> [ 210.593630] rcu_dump_cpu_stacks+0x83/0xb3
> [ 210.593632] rcu_check_callbacks+0x5aa/0x710
> [ 210.593636] ? tick_sched_do_timer+0x50/0x50
> [ 210.593638] update_process_times+0x23/0x50
> [ 210.593640] tick_sched_handle+0x2f/0x40
> [ 210.593642] tick_sched_timer+0x32/0x70
> [ 210.593644] __hrtimer_run_queues+0xf7/0x270
> [ 210.593646] hrtimer_interrupt+0x11d/0x270
> [ 210.593649] smp_apic_timer_interrupt+0x5d/0x130
> [ 210.593651] apic_timer_interrupt+0xf/0x20
> [ 210.593655] RIP: 0010:pattern_trig_timer_function+0x23/0x100
> [ 210.593657] Code: ff ff eb f6 0f 1f 00 41 54 4c 8d a7 b0 df ff ff 55
> 53 48 89 fb 49 8d ac 24 18 20 00 00 48 89 ef e8 f2 d3 29 00 eb 16 8b 53
> f4 <8b> 08 39 ca 77 05 83 f9 31 77 6d 4c 89 e7 e8 aa f9 ff ff 80 7b f8
> [ 210.593658] RSP: 0018:ffff8d1017903eb8 EFLAGS: 00000216 ORIG_RAX:
> ffffffffffffff13
> [ 210.593659] RAX: ffff8d0fe7330010 RBX: ffff8d0fe7332050 RCX:
> 0000000000000031
> [ 210.593660] RDX: 0000000000000000 RSI: 0000000000000014 RDI:
> 000000000000000a
> [ 210.593661] RBP: ffff8d0fe7332018 R08: ffff8d1017903f08 R09:
> ffff8d1017903f08
> [ 210.593662] R10: 0000002c1cd5e92f R11: 0000000000000000 R12:
> ffff8d0fe7330000
> [ 210.593663] R13: ffffffffaa738a70 R14: 0000000000000000 R15:
> 0000000000000001
> [ 210.593665] ? apic_timer_interrupt+0xa/0x20
> [ 210.593666] ? pattern_trig_activate+0xc0/0xc0
> [ 210.593669] ? pattern_trig_timer_function+0x36/0x100
> [ 210.593671] call_timer_fn+0x26/0x130
> [ 210.593672] run_timer_softirq+0x1cc/0x400
> [ 210.593674] ? enqueue_hrtimer+0x35/0x90
> [ 210.593676] ? __hrtimer_run_queues+0x127/0x270
> [ 210.593679] ? recalibrate_cpu_khz+0x10/0x10
> [ 210.593681] __do_softirq+0x104/0x2a5
> [ 210.593685] irq_exit+0x9d/0xa0
> [ 210.593687] smp_apic_timer_interrupt+0x67/0x130
> [ 210.593688] apic_timer_interrupt+0xf/0x20
> [ 210.593689] </IRQ>
> [ 210.593693] RIP: 0010:cpuidle_enter_state+0xf8/0x2a0
> [ 210.593694] Code: c7 0f 1f 44 00 00 31 ff e8 65 69 95 ff 80 7c 24 03
> 00 74 12 9c 58 f6 c4 02 0f 85 8c 01 00 00 31 ff e8 7c 41 9a ff fb 4d 29
> e7 <48> ba cf f7 53 e3 a5 9b c4 20 4c 89 f8 4c 89 fd 48 f7 ea 48 c1 fd
> [ 210.593695] RSP: 0018:ffffb0fc00cf7e88 EFLAGS: 00000206 ORIG_RAX:
> ffffffffffffff13
> [ 210.593696] RAX: ffff8d1017920dc0 RBX: ffff8d1014b49c00 RCX:
> 000000000000001f
> [ 210.593697] RDX: 0000000000000000 RSI: 000000c1514cc3a0 RDI:
> 0000000000000000
> [ 210.593698] RBP: 0000000000000001 R08: fffffffbcf10adc2 R09:
> 000000000000afc7
> [ 210.593699] R10: 000000000000003c R11: ffff8d101791fe68 R12:
> 0000002c1d11a32d
> [ 210.593700] R13: 0000000000000001 R14: 0000000000000004 R15:
> 0000000000011a82
> [ 210.593703] ? cpuidle_enter_state+0xdb/0x2a0
> [ 210.593705] do_idle+0x1f5/0x250
> [ 210.593707] cpu_startup_entry+0x6a/0x70
> [ 210.593709] start_secondary+0x183/0x1b0
> [ 210.593711] secondary_startup_64+0xa4/0xb0
>
> Probably the best solution would be to avoid the dimming if
> delta_t is lower than UPDATE_INTERVAL.
Thanks for your testing. Yes, I will valid the delta_t value when user
use the gradual dimming, and add some comments in ABI to make it
clear, that we should not set delta_t lower than UPDATE_INTERVAL for
gradual dimming.
>
> Besides the above, please refer also to my comments below.
>
> On 09/27/2018 07:04 AM, Baolin Wang wrote:
>> This patch adds one new led trigger that LED device can configure
>> the software or hardware pattern and trigger it.
>>
>> Consumers can write 'pattern' file to enable the software pattern
>> which alters the brightness for the specified duration with one
>> software timer.
>>
>> Moreover consumers can write 'hw_pattern' file to enable the hardware
>> pattern for some LED controllers which can autonomously control
>> brightness over time, according to some preprogrammed hardware
>> patterns.
>>
>> Signed-off-by: Raphael Teysseyre <rteysseyre@xxxxxxxxx>
>> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
>> ---
>> Changes from v12:
>> - Add gradual dimming support for software pattern.
>>
>> Changes from v11:
>> - Change -1 means repeat indefinitely.
>>
>> Changes from v10:
>> - Change 'int' to 'u32' for delta_t field.
>>
>> Changes from v9:
>> - None.
>>
>> Changes from v8:
>> - None.
>>
>> Changes from v7:
>> - Move the SC27XX hardware patterns description into its own ABI file.
>>
>> Changes from v6:
>> - Improve commit message.
>> - Optimize the description of the hw_pattern file.
>> - Simplify some logics.
>>
>> Changes from v5:
>> - Add one 'hw_pattern' file for hardware patterns.
>>
>> Changes from v4:
>> - Change the repeat file to return the originally written number.
>> - Improve comments.
>> - Fix some build warnings.
>>
>> Changes from v3:
>> - Reset pattern number to 0 if user provides incorrect pattern string.
>> - Support one pattern.
>>
>> Changes from v2:
>> - Remove hardware_pattern boolen.
>> - Chnage the pattern string format.
>>
>> Changes from v1:
>> - Use ATTRIBUTE_GROUPS() to define attributes.
>> - Introduce hardware_pattern flag to determine if software pattern
>> or hardware pattern.
>> - Re-implement pattern_trig_store_pattern() function.
>> - Remove pattern_get() interface.
>> - Improve comments.
>> - Other small optimization.
>> ---
>> .../ABI/testing/sysfs-class-led-trigger-pattern | 74 ++++
>> drivers/leds/trigger/Kconfig | 7 +
>> drivers/leds/trigger/Makefile | 1 +
>> drivers/leds/trigger/ledtrig-pattern.c | 406 ++++++++++++++++++++
>> include/linux/leds.h | 15 +
>> 5 files changed, 503 insertions(+)
>> create mode 100644 Documentation/ABI/testing/sysfs-class-led-trigger-pattern
>> create mode 100644 drivers/leds/trigger/ledtrig-pattern.c
>>
>> diff --git a/Documentation/ABI/testing/sysfs-class-led-trigger-pattern b/Documentation/ABI/testing/sysfs-class-led-trigger-pattern
>> new file mode 100644
>> index 0000000..e84d42a
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-class-led-trigger-pattern
>> @@ -0,0 +1,74 @@
>> +What: /sys/class/leds/<led>/pattern
>> +Date: September 2018
>> +KernelVersion: 4.20
>> +Description:
>> + Specify a software pattern for the LED, that supports altering
>> + the brightness for the specified duration with one software
>> + timer. It can do gradual dimming and constant brightness.
>> +
>> + The pattern is given by a series of tuples, of brightness and
>> + duration (ms). The LED is expected to traverse the series and
>> + each brightness value for the specified duration. Duration of
>> + 0 means brightness should immediately change to new value.
>> +
>> + 1. The gradual dimming format of the software pattern values
>> + should be:
>> + "brightness_1 duration_1 brightness_2 duration_2 brightness_3
>> + duration_3 ...". For example:
>> +
>> + echo 0 1000 255 2000 > pattern
>> +
>> + It will make the LED go gradually from zero-intensity to max (255)
>> + intensity in 1000 milliseconds, then back to zero intensity in 2000
>> + milliseconds:
>> +
>> + LED brightness
>> + ^
>> + 255-| / \ / \ /
>> + | / \ / \ /
>> + | / \ / \ /
>> + | / \ / \ /
>> + 0-| / \/ \/
>> + +---0----1----2----3----4----5----6------------> time (s)
>> +
>> + 2. To make the LED go instantly from one brigntess value to another,
>> + we should use use zero-time lengths. So the format should be:
>> + "brightness_1 duration_1 brightness_1 0 brightness_2 duration_2
>> + brightness_2 0 ...". For example:
>> +
>> + echo 0 1000 0 0 255 2000 255 0 > pattern
>> +
>> + It will make the LED stay off for one second, then stay at max brightness
>> + for two seconds:
>> +
>> + LED brightness
>> + ^
>> + 255-| +---------+ +---------+
>> + | | | | |
>> + | | | | |
>> + | | | | |
>> + 0-| -----+ +----+ +----
>> + +---0----1----2----3----4----5----6------------> time (s)
>> +
>> +What: /sys/class/leds/<led>/hw_pattern
>> +Date: September 2018
>> +KernelVersion: 4.20
>> +Description:
>> + Specify a hardware pattern for the LED, for LED hardware that
>> + supports autonomously controlling brightness over time, according
>> + to some preprogrammed hardware patterns.
>> +
>> + Since different LED hardware can have different semantics of
>> + hardware patterns, each driver is expected to provide its own
>> + description for the hardware patterns in their ABI documentation
>> + file.
>> +
>> +What: /sys/class/leds/<led>/repeat
>> +Date: September 2018
>> +KernelVersion: 4.20
>> +Description:
>> + Specify a pattern repeat number. -1 means repeat indefinitely,
>> + other negative numbers and number 0 are invalid.
>> +
>> + This file will always return the originally written repeat
>> + number.
>> diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
>> index 4018af7..b76fc3c 100644
>> --- a/drivers/leds/trigger/Kconfig
>> +++ b/drivers/leds/trigger/Kconfig
>> @@ -129,4 +129,11 @@ config LEDS_TRIGGER_NETDEV
>> This allows LEDs to be controlled by network device activity.
>> If unsure, say Y.
>>
>> +config LEDS_TRIGGER_PATTERN
>> + tristate "LED Pattern Trigger"
>> + help
>> + This allows LEDs to be controlled by a software or hardware pattern
>> + which is a series of tuples, of brightness and duration (ms).
>> + If unsure, say N
>> +
>> endif # LEDS_TRIGGERS
>> diff --git a/drivers/leds/trigger/Makefile b/drivers/leds/trigger/Makefile
>> index f3cfe19..9bcb64e 100644
>> --- a/drivers/leds/trigger/Makefile
>> +++ b/drivers/leds/trigger/Makefile
>> @@ -13,3 +13,4 @@ obj-$(CONFIG_LEDS_TRIGGER_TRANSIENT) += ledtrig-transient.o
>> obj-$(CONFIG_LEDS_TRIGGER_CAMERA) += ledtrig-camera.o
>> obj-$(CONFIG_LEDS_TRIGGER_PANIC) += ledtrig-panic.o
>> obj-$(CONFIG_LEDS_TRIGGER_NETDEV) += ledtrig-netdev.o
>> +obj-$(CONFIG_LEDS_TRIGGER_PATTERN) += ledtrig-pattern.o
>> diff --git a/drivers/leds/trigger/ledtrig-pattern.c b/drivers/leds/trigger/ledtrig-pattern.c
>> new file mode 100644
>> index 0000000..7aba30e
>> --- /dev/null
>> +++ b/drivers/leds/trigger/ledtrig-pattern.c
>> @@ -0,0 +1,406 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +
>> +/*
>> + * LED pattern trigger
>> + *
>> + * Idea discussed with Pavel Machek. Raphael Teysseyre implemented
>> + * the first version, Baolin Wang simplified and improved the approach.
>> + */
>> +
>> +#include <linux/kernel.h>
>> +#include <linux/leds.h>
>> +#include <linux/module.h>
>> +#include <linux/mutex.h>
>> +#include <linux/slab.h>
>> +#include <linux/timer.h>
>> +
>> +#define MAX_PATTERNS 1024
>> +/*
>> + * When doing gradual dimming, the led brightness will be updated
>> + * every 50 milliseconds.
>> + */
>> +#define UPDATE_INTERVAL 50
>> +
>> +struct pattern_trig_data {
>> + struct led_classdev *led_cdev;
>> + struct led_pattern patterns[MAX_PATTERNS];
>> + struct led_pattern *curr;
>> + struct led_pattern *next;
>> + struct mutex lock;
>> + u32 npatterns;
>> + int repeat;
>> + int last_repeat;
>> + int delta_t;
>> + bool is_indefinite;
>> + bool is_hw_pattern;
>> + struct timer_list timer;
>> +};
>> +
>> +static void pattern_trig_update_patterns(struct pattern_trig_data *data)
>> +{
>> + data->curr = data->next;
>> + if (!data->is_indefinite && data->curr == data->patterns)
>> + data->repeat--;
>> +
>> + if (data->next == data->patterns + data->npatterns - 1)
>> + data->next = data->patterns;
>> + else
>> + data->next++;
>> +
>> + data->delta_t = 0;
>> +}
>> +
>> +static int pattern_trig_compute_brightness(struct pattern_trig_data *data)
>> +{
>> + int step_brightness;
>> +
>> + if (data->delta_t == 0)
>> + return data->curr->brightness;
>> +
>> + step_brightness = abs(data->next->brightness - data->curr->brightness);
>> + step_brightness = data->delta_t * step_brightness / data->curr->delta_t;
>> +
>> + if (data->next->brightness > data->curr->brightness)
>> + return data->curr->brightness + step_brightness;
>> + else
>> + return data->curr->brightness - step_brightness;
>> +}
>> +
>> +static void pattern_trig_timer_function(struct timer_list *t)
>> +{
>> + struct pattern_trig_data *data = from_timer(data, t, timer);
>> +
>> + mutex_lock(&data->lock);
>> +
>> +try_again:
>> + if (!data->is_indefinite && !data->repeat) {
>> + mutex_unlock(&data->lock);
>> + return;
>> + }
>
> Let's change try_again label to "for (;;) {" here (it seems that
> above condition needs to be evaluated only on enter to this function).
Sure.
>
>> + if (data->curr->brightness == data->next->brightness) {
>> + /* Constant brightness */
>> + led_set_brightness(data->led_cdev, data->curr->brightness);
>> + mod_timer(&data->timer,
>> + jiffies + msecs_to_jiffies(data->curr->delta_t));
>> +
>> + /* Skip the step with zero duration */
>> + pattern_trig_update_patterns(data);
>> + /* Select next step */
>> + pattern_trig_update_patterns(data);
>> + } else {
>> + /* Gradual dimming */
>> +
>> + /*
>> + * If the accumulation time is larger than current step
>> + * duration, we should go next one and re-check if we
>> + * repeated done.
>> + */
>> + if (data->delta_t > data->curr->delta_t) {
>> + pattern_trig_update_patterns(data);
>> + goto try_again;
>
> When in for (;;) loop, we can "continue" here instead.
Yes.
>
>> + }
>> +
>> + /*
>> + * If current step duration is less than UPDATE_INTERVAL, we
>> + * should go next one and re-check if we repeated done.
>> + */
>> + if (data->curr->delta_t < UPDATE_INTERVAL) {
>> + pattern_trig_update_patterns(data);
>> + goto try_again;
>
> Ditto.
>
>> + }
>> +
>> + led_set_brightness(data->led_cdev,
>> + pattern_trig_compute_brightness(data));
>> + mod_timer(&data->timer,
>> + jiffies + msecs_to_jiffies(UPDATE_INTERVAL));
>> + /* Accumulate the gradual dimming time */
>> + data->delta_t += UPDATE_INTERVAL;
>> + }
>
> When in for (;;) loop we should "break" here.
Yes.
>
>> + mutex_unlock(&data->lock);
>> +}
>> +
>> +static int pattern_trig_start_pattern(struct led_classdev *led_cdev)
>> +{
>> + struct pattern_trig_data *data = led_cdev->trigger_data;
>> +
>> + if (!data->npatterns)
>> + return 0;
>> +
>> + if (data->is_hw_pattern) {
>> + return led_cdev->pattern_set(led_cdev, data->patterns,
>> + data->npatterns, data->repeat);
>> + }
>> +
>> + data->delta_t = 0;
>> + data->curr = data->patterns;
>> + data->next = data->npatterns > 1 ? data->patterns + 1 : data->patterns;
>> + data->timer.expires = jiffies;
>> + add_timer(&data->timer);
>> +
>> + return 0;
>> +}
>> +
>> +static ssize_t repeat_show(struct device *dev, struct device_attribute *attr,
>> + char *buf)
>> +{
>> + struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> + struct pattern_trig_data *data = led_cdev->trigger_data;
>> + int repeat;
>> +
>> + mutex_lock(&data->lock);
>> +
>> + repeat = data->last_repeat;
>
> I'm not sure if we discussed it earlier, but currently repeat_show
> always reports initially requested repeat number, instead of the
> number of remaining iterations. IMHO the latter approach would be
> more useful.
That's what we discussed before and had a consensus about this. Please see:
https://lore.kernel.org/patchwork/patch/971746/
Thanks.
--
Baolin Wang
Best Regards