linux-kernel - Re: [PATCH v6 2/4] leds: Add driver for Qualcomm LPG

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Date:   Thu, 29 Oct 2020 19:13:57 +0100
From:   Pavel Machek <pavel@....cz>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Dan Murphy <dmurphy@...com>, Rob Herring <robh+dt@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Lee Jones <lee.jones@...aro.org>,
        Martin Botka <martin.botka1@...il.com>,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-pwm@...r.kernel.org
Subject: Re: [PATCH v6 2/4] leds: Add driver for Qualcomm LPG

Hi!

> The Light Pulse Generator (LPG) is a PWM-block found in a wide range of
> PMICs from Qualcomm. It can operate on fixed parameters or based on a
> lookup-table, altering the duty cycle over time - which provides the
> means for e.g. hardware assisted transitions of LED brightness.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---
> 
> Changes since v5:
> - Make sure to not used the state of the last channel in a group to determine
>   if the current sink should be active for all channels in the group.
> - Replacement of unsigned -1 with UINT_MAX
> - Work around potential overflow by using larger data types, instead of separate code paths
> - Use cpu_to_l16() rather than hand rolling them
> - Minor style cleanups
> 
>  drivers/leds/Kconfig         |    9 +
>  drivers/leds/Makefile        |    1 +
>  drivers/leds/leds-qcom-lpg.c | 1190 ++++++++++++++++++++++++++++++++++
>  3 files changed, 1200 insertions(+)
>  create mode 100644 drivers/leds/leds-qcom-lpg.c

Let's put this into drivers/leds/rgb/. You may need to create it.


> +static int lpg_lut_store(struct lpg *lpg, struct led_pattern *pattern,
> +			 size_t len, unsigned int *lo_idx, unsigned int *hi_idx)
> +{
> +	unsigned int idx;
> +	__le16 val;

No need for __XX variants outside of headers meant for userspace.

> +#define LPG_ENABLE_GLITCH_REMOVAL	BIT(5)
> +
> +static void lpg_enable_glitch(struct lpg_channel *chan)
> +{
> +	struct lpg *lpg = chan->lpg;
> +
> +	regmap_update_bits(lpg->map, chan->base + PWM_TYPE_CONFIG_REG,
> +			   LPG_ENABLE_GLITCH_REMOVAL, 0);
> +}
> +
> +static void lpg_disable_glitch(struct lpg_channel *chan)
> +{
> +	struct lpg *lpg = chan->lpg;
> +
> +	regmap_update_bits(lpg->map, chan->base + PWM_TYPE_CONFIG_REG,
> +			   LPG_ENABLE_GLITCH_REMOVAL,
> +			   LPG_ENABLE_GLITCH_REMOVAL);
> +}

Helper functions for single register write is kind of overkill...

> +static int lpg_blink_set(struct lpg_led *led,
> +			 unsigned long delay_on, unsigned long delay_off)
> +{
> +	struct lpg_channel *chan;
> +	unsigned int period_us;
> +	unsigned int duty_us;
> +	int i;
> +
> +	if (!delay_on && !delay_off) {
> +		delay_on = 500;
> +		delay_off = 500;
> +	}

Aren't you supposed to modify the values passed to you, so that
userspace knows what the default rate is?


> +	ret = lpg_lut_store(lpg, pattern, len, &lo_idx, &hi_idx);
> +	if (ret < 0)
> +		goto out;

Just do direct return.

> +out:
> +	return ret;
> +}

> +static const struct pwm_ops lpg_pwm_ops = {
> +	.request = lpg_pwm_request,
> +	.apply = lpg_pwm_apply,
> +	.owner = THIS_MODULE,
> +};
> +
> +static int lpg_add_pwm(struct lpg *lpg)
> +{
> +	int ret;
> +
> +	lpg->pwm.base = -1;
> +	lpg->pwm.dev = lpg->dev;
> +	lpg->pwm.npwm = lpg->num_channels;
> +	lpg->pwm.ops = &lpg_pwm_ops;
> +
> +	ret = pwmchip_add(&lpg->pwm);
> +	if (ret)
> +		dev_err(lpg->dev, "failed to add PWM chip: ret %d\n", ret);
> +
> +	return ret;
> +}

Do we need to do this? I'd rather have LED driver, than LED+PWM
driver...

Best regards,
							Pavel
-- 
http://www.livejournal.com/~pavelmachek

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