linux-kernel - Re: [PATCH v7 2/6] leds: Add driver for Qualcomm LPG

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Message-ID: <20210502211542.GE2484@yoga>
Date:   Sun, 2 May 2021 16:15:42 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Marijn Suijten <marijn.suijten@...ainline.org>
Cc:     Pavel Machek <pavel@....cz>, Rob Herring <robh+dt@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-K?nig <u.kleine-koenig@...gutronix.de>,
        Lee Jones <lee.jones@...aro.org>, 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,
        Yassine Oudjana <y.oudjana@...tonmail.com>,
        Luca Weiss <luca@...tu.xyz>,
        Subbaraman Narayanamurthy <subbaram@...eaurora.org>
Subject: Re: [PATCH v7 2/6] leds: Add driver for Qualcomm LPG

On Sat 01 May 16:09 CDT 2021, Marijn Suijten wrote:

> Hi Bjorn,
> 
> On 4/29/21 11:15 PM, Bjorn Andersson wrote:
> > 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 v6:
> > - Moved code into drivers/leds/rgb/
> > - Reverted to earlier qcom,dtest handling to support routing pwm signals
> >    through dtest lines.
> > - Remember the duration of each step of the pattern, rather than adding up and
> >    then dividing when the value is used.
> > - Added missing error prints on DT parse errors.
> > - Added sm8150[lb] and made led source and atc presence optional
> > - Added missing parenthesis around (len + 1) / 2 in search for hi_pause in the
> >    pattern.
> > 
> >   drivers/leds/Kconfig             |    3 +
> >   drivers/leds/Makefile            |    3 +
> >   drivers/leds/rgb/leds-qcom-lpg.c | 1286 ++++++++++++++++++++++++++++++
> >   3 files changed, 1292 insertions(+)
> >   create mode 100644 drivers/leds/rgb/leds-qcom-lpg.c
> > 
> > diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
> > index 49d99cb084db..8ab06b3f162d 100644
> > --- a/drivers/leds/Kconfig
> > +++ b/drivers/leds/Kconfig
> > @@ -933,6 +933,9 @@ source "drivers/leds/blink/Kconfig"
> >   comment "Flash and Torch LED drivers"
> >   source "drivers/leds/flash/Kconfig"
> > +comment "RGB LED drivers"
> > +source "drivers/leds/rgb/Kconfig"
> 
> 
> It looks like this file is not included in any of the patches.
> 

Sorry about that, seems like I missed adding them to the commit :(

> > +
> >   comment "LED Triggers"
> >   source "drivers/leds/trigger/Kconfig"
> > diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
> > index 7e604d3028c8..8cad0465aae0 100644
> > --- a/drivers/leds/Makefile
> > +++ b/drivers/leds/Makefile
> > @@ -106,6 +106,9 @@ obj-$(CONFIG_LEDS_USER)			+= uleds.o
> >   # Flash and Torch LED Drivers
> >   obj-$(CONFIG_LEDS_CLASS_FLASH)		+= flash/
> > +# RGB LED Drivers
> > +obj-$(CONFIG_LEDS_CLASS_MULTICOLOR)	+= rgb/
> 
> 
> This file appears to be missing from this patch(set), too.
> 

Right, missed both the new files.

> > +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;
> > +	u16 val;
> > +	int i;
> > +
> > +	/* Hardware does not behave when LO_IDX == HI_IDX */
> > +	if (len == 1)
> > +		return -EINVAL;
> > +
> > +	idx = bitmap_find_next_zero_area(lpg->lut_bitmap, lpg->lut_size,
> > +					 0, len, 0);
> > +	if (idx >= lpg->lut_size)
> > +		return -ENOMEM;
> > +
> > +	for (i = 0; i < len; i++) {
> > +		val = pattern[i].brightness;
> > +
> > +		regmap_bulk_write(lpg->map, lpg->lut_base + LPG_LUT_REG(idx + i), &val, 1);
> 
> 
> This and the other regmap_bulk_write in lpg_apply_pwm_value used sizeof(val)
> before.  As far as I'm aware qcom-spmi-pmic specifies 16-bit addresses
> (.reg_bits) but 8-bit register sizes (.val_bits).  Writing one register
> means only 8 out of 16 bits in u16 val are written?
> 

You're right and I should have used test pattern that shown that I lost
that 9th bit...

I'll restore the sizeof()

> > +static void lpg_apply_lut_control(struct lpg_channel *chan)
> > +{
> > +	struct lpg *lpg = chan->lpg;
> > +	unsigned int hi_pause;
> > +	unsigned int lo_pause;
> > +	unsigned int step;
> > +	unsigned int conf = 0;
> > +	unsigned int lo_idx = chan->pattern_lo_idx;
> > +	unsigned int hi_idx = chan->pattern_hi_idx;
> > +	int pattern_len;
> > +
> > +	if (!chan->ramp_enabled || chan->pattern_lo_idx == chan->pattern_hi_idx)
> > +		return;
> > +
> > +	pattern_len = hi_idx - lo_idx + 1 > +
> > +	step = chan->ramp_tick_ms;
> 
> 
> Since this is not dividing a full pattern duration by pattern_len anymore,
> that variable is now never read and best removed.
> 

Ok

> > +static int lpg_parse_channel(struct lpg *lpg, struct device_node *np,
> > +			     struct lpg_channel **channel)
> > +{
> > +	struct lpg_channel *chan;
> > +	u32 color = LED_COLOR_ID_GREEN;
> > +	u32 reg;
> > +	int ret;
> > +
> > +	ret = of_property_read_u32(np, "reg", &reg);
> > +	if (ret || !reg || reg > lpg->num_channels) {
> > +		dev_err(lpg->dev, "invalid reg of %pOFn\n", np);
> 
> 
> Like \"color\" below, escape reg with \"reg\"?
> 

Sounds good.

> > +static int lpg_add_led(struct lpg *lpg, struct device_node *np)
> > +{
> > +	struct led_classdev *cdev;
> > +	struct device_node *child;
> > +	struct mc_subled *info;
> > +	struct lpg_led *led;
> > +	const char *state;
> > +	int num_channels;
> > +	u32 color = 0;
> > +	int ret;
> > +	int i;
> > +
> > +	ret = of_property_read_u32(np, "color", &color);
> > +	if (ret < 0 && ret != -EINVAL) {
> > +		dev_err(lpg->dev, "failed to parse \"color\" of %pOF\n", np);
> > +		return ret;
> > +	}
> > +
> > +	if (color == LED_COLOR_ID_MULTI)
> 
> 
> Since this driver now lives under rgb/, and is specifically for RGB leds
> (afaik), should this and the rest of the code use LED_COLOR_ID_RGB instead?
> There was a patch floating around on (if I remember correctly) ##linux-msm
> by Luca Weiss that performs the conversion, with some related changes.
> 

I thought MULTICOLOR was the right color, but reading the comment on the
defines it seems RGB is the color I actually want. Will check out
z3ntu's changes as well.

> > +static int lpg_init_lut(struct lpg *lpg)
> > +{
> > +	const struct lpg_data *data = lpg->data;
> > +	size_t bitmap_size;
> > +
> > +	if (!data->lut_base)
> > +		return 0;
> > +
> > +	lpg->lut_base = data->lut_base;
> > +	lpg->lut_size = data->lut_size;
> > +
> > +	bitmap_size = BITS_TO_BYTES(lpg->lut_size);
> > +	lpg->lut_bitmap = devm_kzalloc(lpg->dev, bitmap_size, GFP_KERNEL);
> > +	if (!lpg->lut_bitmap)
> > +		return -ENOMEM;
> > +
> > +	bitmap_clear(lpg->lut_bitmap, 0, lpg->lut_size);
> 
> 
> devm_kzalloc already zeroes the bitmap.  Is it necessary to clear it again
> (assuming a "cleared" bitmap is implementation-dependent and does not imply
> zeroed memory) or could the memory be allocated with devm_kalloc instead?
> 

You're right, I can drop the explicit clear of the bitmap.

Thanks,
Bjorn