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Message-id: <576A3DB5.4080703@samsung.com>
Date: Wed, 22 Jun 2016 09:26:45 +0200
From: Jacek Anaszewski <j.anaszewski@...sung.com>
To: Florian Vaussard <florian.vaussard@...g-vd.ch>
Cc: Florian Vaussard <florian.vaussard@...il.com>,
devicetree@...r.kernel.org, Richard Purdie <rpurdie@...ys.net>,
Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>,
linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] leds: Add driver for NCP5623 3-channel I2C LED driver
Hi Florian,
On 06/22/2016 08:08 AM, Florian Vaussard wrote:
> Hi Jacek,
>
> Le 21. 06. 16 à 17:29, Jacek Anaszewski a écrit :
>> Hi Florian,
>>
>> Thanks for the patch. Please refer to my comments in the code.
>>
>
> Thanks for your review. I completely agree with you, I will address your
> comments in V2. I just have one small question below.
>
>> On 06/21/2016 09:29 AM, Florian Vaussard wrote:
>>> The NCP5623 is a 3-channel LED driver from On Semiconductor controlled
>>> through I2C. The PWM of each channel can be independently set with 32
>>> distinct levels. In addition, the intensity of the current source can be
>>> globally set using an external bias resistor fixing the reference
>>> current (Iref) and a dedicated register (ILED), following the
>>> relationship:
>>>
>>> I = 2400*Iref/(31-ILED)
>>>
>>> with Iref = Vref/Rbias, and Vref = 0.6V.
>>>
>>> Signed-off-by: Florian Vaussard <florian.vaussard@...g-vd.ch>
>>> ---
>>> drivers/leds/Kconfig | 11 ++
>>> drivers/leds/Makefile | 1 +
>>> drivers/leds/leds-ncp5623.c | 265 ++++++++++++++++++++++++++++++++++++++++++++
>>> 3 files changed, 277 insertions(+)
>>> create mode 100644 drivers/leds/leds-ncp5623.c
>>>
>>> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
>>> index 5ae2834..6d3e44d 100644
>>> --- a/drivers/leds/Kconfig
>>> +++ b/drivers/leds/Kconfig
>>> @@ -588,6 +588,17 @@ config LEDS_BLINKM
>>> This option enables support for the BlinkM RGB LED connected
>>> through I2C. Say Y to enable support for the BlinkM LED.
>>>
>>> +config LEDS_NCP5623
>>> + tristate "LED Support for NCP5623 I2C chip"
>>> + depends on LEDS_CLASS
>>> + depends on I2C
>>> + help
>>> + This option enables support for LEDs connected to NCP5623
>>> + LED driver chips accessed via the I2C bus.
>>> + Driver supports brightness control.
>>> +
>>> + Say Y to enable this driver.
>>> +
>>> config LEDS_POWERNV
>>> tristate "LED support for PowerNV Platform"
>>> depends on LEDS_CLASS
>>> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
>>> index cb2013d..a2f0e10 100644
>>> --- a/drivers/leds/Makefile
>>> +++ b/drivers/leds/Makefile
>>> @@ -67,6 +67,7 @@ obj-$(CONFIG_LEDS_KTD2692) += leds-ktd2692.o
>>> obj-$(CONFIG_LEDS_POWERNV) += leds-powernv.o
>>> obj-$(CONFIG_LEDS_SEAD3) += leds-sead3.o
>>> obj-$(CONFIG_LEDS_IS31FL32XX) += leds-is31fl32xx.o
>>> +obj-$(CONFIG_LEDS_NCP5623) += leds-ncp5623.o
>>>
>>> # LED SPI Drivers
>>> obj-$(CONFIG_LEDS_DAC124S085) += leds-dac124s085.o
>>> diff --git a/drivers/leds/leds-ncp5623.c b/drivers/leds/leds-ncp5623.c
>>> new file mode 100644
>>> index 0000000..a341e4a
>>> --- /dev/null
>>> +++ b/drivers/leds/leds-ncp5623.c
>>> @@ -0,0 +1,265 @@
>>> +/*
>>> + * Copyright 2016 Florian Vaussard <florian.vaussard@...g-vd.ch>
>>> + *
>>> + * Based on leds-tlc591xx.c
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License as published by
>>> + * the Free Software Foundation; version 2 of the License.
>>> + */
>>> +
>>> +#include <linux/bitops.h>
>>> +#include <linux/i2c.h>
>>> +#include <linux/kernel.h>
>>> +#include <linux/leds.h>
>>> +#include <linux/module.h>
>>> +#include <linux/of.h>
>>> +#include <linux/of_device.h>
>>> +#include <linux/slab.h>
>>> +#include <linux/workqueue.h>
>>> +
>>> +#define NCP5623_MAX_LEDS 3
>>> +#define NCP5623_MAX_STEPS 32
>>> +#define NCP5623_MAX_CURRENT 31
>>> +#define NCP5623_MAX_CURRENT_UA 30000
>>> +
>>> +#define NCP5623_CMD_SHIFT 5
>>> +#define CMD_SHUTDOWN (0x00 << NCP5623_CMD_SHIFT)
>>> +#define CMD_ILED (0x01 << NCP5623_CMD_SHIFT)
>>> +#define CMD_PWM1 (0x02 << NCP5623_CMD_SHIFT)
>>> +#define CMD_PWM2 (0x03 << NCP5623_CMD_SHIFT)
>>> +#define CMD_PWM3 (0x04 << NCP5623_CMD_SHIFT)
>>> +#define CMD_UPWARD_DIM (0x05 << NCP5623_CMD_SHIFT)
>>> +#define CMD_DOWNWARD_DIM (0x06 << NCP5623_CMD_SHIFT)
>>> +#define CMD_DIM_STEP (0x07 << NCP5623_CMD_SHIFT)
>>> +
>>> +#define NCP5623_DATA_MASK GENMASK(NCP5623_CMD_SHIFT - 1, 0)
>>> +
>>> +#define NCP5623_CMD(cmd, data) (cmd | (data & NCP5623_DATA_MASK))
>>> +
>
> [snip]
>
>>> +
>>> +static int ncp5623_configure(struct device *dev,
>>> + struct ncp5623_priv *priv)
>>> +{
>>> + unsigned int i;
>>> + unsigned int n;
>>> + struct ncp5623_led *led;
>>> + int err;
>>> +
>>> + /* Compute the value of ILED register to honor led_max_current */
>>> + n = 2400 * priv->led_iref / priv->led_max_current + 1;
>>> + if (n > NCP5623_MAX_CURRENT)
>>> + n = NCP5623_MAX_CURRENT;
>>> + n = NCP5623_MAX_CURRENT - n;
>>> +
>>> + dev_dbg(dev, "setting maximum current to %u uA\n",
>>> + 2400 * priv->led_iref / (NCP5623_MAX_CURRENT - n));
>>> +
>>> + err = ncp5623_send_cmd(priv, CMD_ILED, n);
>>> + if (err < 0) {
>>> + dev_err(dev, "cannot set the current\n");
>>> + return err;
>>> + }
>>> +
>>> + /* Setup each individual LED */
>>> + for (i = 0; i < NCP5623_MAX_LEDS; i++) {
>>> + led = &priv->leds[i];
>>> +
>>> + if (!led->active)
>>> + continue;
>>> +
>>> + led->priv = priv;
>>> + led->led_no = i;
>>> + led->ldev.brightness_set = ncp5623_brightness_set;
>>> + led->ldev.max_brightness = NCP5623_MAX_STEPS - 1;
>>
>> max_brightness should be asserted according to led-max-microamp
>> property.
>>
>
> We can set two parameters on this chip:
>
> - The intensity of the current source (common to all LEDs) from 0 to
> NCP5623_MAX_CURRENT (31)
> - The PWM for each LED independently from 0 to NCP5623_MAX_STEPS-1 (31)
>
> My understanding was to use the led-max-microamp property to set up the current
> source so that even with a duty cycle of 100% (PWM=31) the LED cannot be
> damaged. In this case, I think that is unnecessary to assert max_brightness, as
> we are guaranteed by design that led-max-microamp will not be surpassed for any
> value of the PWM. Would you suggest another approach?
Yes, if step 31 reflects led-max-microamp value, then max_brightness
should be 31, regardless of led-max-microamp value.
>>> + INIT_WORK(&led->work, ncp5623_led_work);
>>
>> Please remove it and use brightness_set_blocking op.
>>
>>> + err = led_classdev_register(dev, &led->ldev);
>>
>> Use devm prefixed version.
>>
>>> + if (err < 0) {
>>> + dev_err(dev, "couldn't register LED %s\n",
>>> + led->ldev.name);
>>> + goto exit;
>>> + }
>>> + }
>>> +
>>> + return 0;
>>> +
>>> +exit:
>>> + ncp5623_destroy_devices(priv);
>>> + return err;
>>> +}
>>> +
>
>
--
Best regards,
Jacek Anaszewski
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