linux-kernel - Re: [PATCH v17 RESEND 2/3] leds: flash: mt6370: Add MediaTek MT6370 flashlight support

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Message-ID: <20230308135433.GL9667@google.com>
Date:   Wed, 8 Mar 2023 13:54:33 +0000
From:   Lee Jones <lee@...nel.org>
To:     ChiYuan Huang <cy_huang@...htek.com>
Cc:     ChiaEn Wu <chiaen_wu@...htek.com>, corbet@....net, pavel@....cz,
        matthias.bgg@...il.com, andriy.shevchenko@...ux.intel.com,
        jacek.anaszewski@...il.com,
        angelogioacchino.delregno@...labora.com, linux-doc@...r.kernel.org,
        peterwu.pub@...il.com, linux-leds@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        szunichen@...il.com
Subject: Re: [PATCH v17 RESEND 2/3] leds: flash: mt6370: Add MediaTek MT6370
 flashlight support

On Tue, 07 Mar 2023, ChiYuan Huang wrote:

> Hi, Lee:
>    Reply below the comments.
>
> On Sun, Mar 05, 2023 at 10:06:08AM +0000, Lee Jones wrote:
> > On Thu, 23 Feb 2023, ChiaEn Wu wrote:
> >
> > > From: ChiYuan Huang <cy_huang@...htek.com>
> > >
> > > The MediaTek MT6370 is a highly-integrated smart power management IC,
> > > which includes a single cell Li-Ion/Li-Polymer switching battery
> > > charger, a USB Type-C & Power Delivery (PD) controller, dual Flash
> > > LED current sources, a RGB LED driver, a backlight WLED driver,
> > > a display bias driver and a general LDO for portable devices.
> > >
> > > Add support for the MT6370 Flash LED driver. Flash LED in MT6370
> > > has 2 channels and support torch/strobe mode.
> > >
> > > Acked-by: Jacek Anaszewski <jacek.anaszewski@...il.com>
> > > Co-developed-by: Alice Chen <alice_chen@...htek.com>
> > > Signed-off-by: Alice Chen <alice_chen@...htek.com>
> > > Signed-off-by: ChiYuan Huang <cy_huang@...htek.com>
> > > Signed-off-by: ChiaEn Wu <chiaen_wu@...htek.com>
> > > ---
> > > v17
> > > - Update the year of Copyright from 2022 to 2023
> > >
> > > ---
> > >  drivers/leds/flash/Kconfig             |  13 +
> > >  drivers/leds/flash/Makefile            |   1 +
> > >  drivers/leds/flash/leds-mt6370-flash.c | 596 +++++++++++++++++++++++++++++++++
> > >  3 files changed, 610 insertions(+)
> > >  create mode 100644 drivers/leds/flash/leds-mt6370-flash.c

[...]

> > > +static int _mt6370_flash_brightness_set(struct led_classdev_flash *fl_cdev,
> > > +					u32 brightness)
> > > +{
> > > +	struct mt6370_led *led = to_mt6370_led(fl_cdev, flash);
> > > +	struct mt6370_priv *priv = led->priv;
> > > +	struct led_flash_setting *setting = &fl_cdev->brightness;
> > > +	u32 val = (brightness - setting->min) / setting->step;
> > > +	int ret, i;
> > > +
> > > +	if (led->led_no == MT6370_LED_JOINT) {
> >
> > What is a "JOINT"?
> >
> Since MT6370 has two flash led channels. Per channel can drive the current up to 1.5A.
> 'JOINT' case is used if 1.5A driving current is not enough, like as flash current 2A.
> They can use two channels to drive 'one' flash led by the HW application.
> This will make the driving current larger than the capability of one channel.

Is "joint" the term used in the datasheet?

Please make this definition clear in the code.

If I'm asking, others are likely to too.

[...]

> > > +static int mt6370_init_flash_properties(struct device *dev,
> > > +					struct mt6370_led *led,
> > > +					struct fwnode_handle *fwnode)
> > > +{
> > > +	struct led_classdev_flash *flash = &led->flash;
> > > +	struct led_classdev *lcdev = &flash->led_cdev;
> > > +	struct mt6370_priv *priv = led->priv;
> > > +	struct led_flash_setting *s;
> > > +	u32 sources[MT6370_MAX_LEDS];
> > > +	u32 max_ua, val;
> > > +	int i, ret, num;
> > > +
> > > +	num = fwnode_property_count_u32(fwnode, "led-sources");
> > > +	if (num < 1)
> > > +		return dev_err_probe(dev, -EINVAL,
> > > +				     "Not specified or wrong number of led-sources\n");
> > > +
> > > +	ret = fwnode_property_read_u32_array(fwnode, "led-sources", sources, num);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	for (i = 0; i < num; i++) {
> > > +		if (sources[i] >= MT6370_MAX_LEDS)
> > > +			return -EINVAL;
> > > +		if (priv->leds_active & BIT(sources[i]))
> > > +			return -EINVAL;
> > > +		priv->leds_active |= BIT(sources[i]);
> > > +	}
> > > +
> > > +	led->led_no = num == 2 ? MT6370_LED_JOINT : sources[0];
> > > +
> > > +	max_ua = num == 2 ? MT6370_ITORCH_DOUBLE_MAX_uA : MT6370_ITORCH_MAX_uA;
> > > +	val = MT6370_ITORCH_MIN_uA;
> >
> > In what scenario does this not get overwritten?
> >
> Only if the property is missing. This will make the value keep in minimum.

If the property is missing, fwnode_property_read_u32() returns an errno, no?

If that's the case, val will be over-written in the if() clause?

--
Lee Jones [李琼斯]