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Date: Wed, 22 Jun 2016 08:08:08 +0200
From: Florian Vaussard <florian.vaussard@...g-vd.ch>
To: Jacek Anaszewski <j.anaszewski@...sung.com>,
Florian Vaussard <florian.vaussard@...il.com>
CC: <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 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?
>> + 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;
>> +}
>> +
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