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Date: Sun, 18 Oct 2020 23:12:59 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Bjorn Andersson <bjorn.andersson@...aro.org>
Cc: Pavel Machek <pavel@....cz>, 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 LED Subsystem <linux-leds@...r.kernel.org>,
devicetree <devicetree@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-arm-msm@...r.kernel.org, linux-pwm@...r.kernel.org
Subject: Re: [PATCH v5 2/4] leds: Add driver for Qualcomm LPG
On Sat, Oct 17, 2020 at 8:41 AM Bjorn Andersson
<bjorn.andersson@...aro.org> 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.
> +config LEDS_QCOM_LPG
> + tristate "LED support for Qualcomm LPG"
> + depends on LEDS_CLASS_MULTICOLOR
> + depends on OF
> + depends on SPMI
> +#include <linux/of.h>
> +#include <linux/of_device.h>
...
> +struct lpg {
> + struct device *dev;
> + struct regmap *map;
Can't you derive the former from the latter?
> +
> + struct pwm_chip pwm;
> +
> + const struct lpg_data *data;
> +
> + u32 lut_base;
> + u32 lut_size;
> + unsigned long *lut_bitmap;
> +
> + u32 triled_base;
> + u32 triled_src;
> +
> + struct lpg_channel *channels;
> + unsigned int num_channels;
> +};
...
> +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;
> + u8 val[2];
__be16 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[0] = pattern[i].brightness & 0xff;
> + val[1] = pattern[i].brightness >> 8;
cpu_to_be16();
> +
> + regmap_bulk_write(lpg->map,
> + lpg->lut_base + LPG_LUT_REG(idx + i), val, 2);
> + }
> +
> + bitmap_set(lpg->lut_bitmap, idx, len);
> +
> + *lo_idx = idx;
> + *hi_idx = idx + len - 1;
> +
> + return 0;
> +}
...
> +static void lpg_calc_freq(struct lpg_channel *chan, unsigned int period_us)
> +{
> + int n, m, clk, div;
> + int best_m, best_div, best_clk;
> + unsigned int last_err, cur_err, min_err;
> + unsigned int tmp_p, period_n;
> +
> + if (period_us == chan->period_us)
> + return;
> +
> + /* PWM Period / N */
> + if (period_us < ((unsigned int)(-1) / NSEC_PER_USEC)) {
Please, replace all these -1 with castings to unsigned types with
corresponding limits, like
UINT_MAX here.
> + period_n = (period_us * NSEC_PER_USEC) >> 6;
> + n = 6;
> + } else {
> + period_n = (period_us >> 9) * NSEC_PER_USEC;
> + n = 9;
> + }
Why inconsistency in branches? Can you rather derive n and calculate
only once like
period_n = (period_us >> n) * NSEC_PER_USEC;
?
> + min_err = (unsigned int)(-1);
> + last_err = (unsigned int)(-1);
> + best_m = 0;
> + best_clk = 0;
> + best_div = 0;
> + for (clk = 0; clk < NUM_PWM_CLK; clk++) {
> + for (div = 0; div < NUM_PWM_PREDIV; div++) {
> + /* period_n = (PWM Period / N) */
> + /* tmp_p = (Pre-divide * Clock Period) * 2^m */
> + tmp_p = lpg_clk_table[div][clk];
> + for (m = 0; m <= NUM_EXP; m++) {
> + if (period_n > tmp_p)
> + cur_err = period_n - tmp_p;
> + else
> + cur_err = tmp_p - period_n;
> +
> + if (cur_err < min_err) {
> + min_err = cur_err;
> + best_m = m;
> + best_clk = clk;
> + best_div = div;
> + }
> +
> + if (m && cur_err > last_err)
> + /* Break for bigger cur_err */
> + break;
> +
> + last_err = cur_err;
> + tmp_p <<= 1;
> + }
> + }
> + }
> +
> + /* Use higher resolution */
> + if (best_m >= 3 && n == 6) {
> + n += 3;
> + best_m -= 3;
> + }
> +
> + chan->clk = best_clk;
> + chan->pre_div = best_div;
> + chan->pre_div_exp = best_m;
> + chan->pwm_size = n;
> +
> + chan->period_us = period_us;
> +}
> +
> +static void lpg_calc_duty(struct lpg_channel *chan, unsigned int duty_us)
> +{
> + unsigned long max = (1 << chan->pwm_size) - 1;
BIT() ?
> + unsigned long val;
> +
> + /* Figure out pwm_value with overflow handling */
> + if (duty_us < 1 << (sizeof(val) * 8 - chan->pwm_size))
BITS_PER_TYPE, but actually BITS_PER_LONG here.
BIT(BITS_PER_LONG - ...)
> + val = (duty_us << chan->pwm_size) / chan->period_us;
> + else
> + val = duty_us / (chan->period_us >> chan->pwm_size);
> +
> + if (val > max)
> + val = max;
> +
> + chan->pwm_value = val;
> +}
...
> +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);
> +}
Here and everywhere else when function declared as void there is no
possibility to know if we do something useful or already screwed up
the things.
> +static void lpg_apply_pwm_value(struct lpg_channel *chan)
> +{
> + u8 val[] = { chan->pwm_value & 0xff, chan->pwm_value >> 8 };
__le16 and cpu_to_le16()
> + struct lpg *lpg = chan->lpg;
> +
> + if (!chan->enabled)
> + return;
> +
> + regmap_bulk_write(lpg->map, chan->base + PWM_VALUE_REG, val, 2);
> +}
> +#define LPG_PATTERN_CONFIG_LO_TO_HI BIT(4)
> +#define LPG_PATTERN_CONFIG_REPEAT BIT(3)
> +#define LPG_PATTERN_CONFIG_TOGGLE BIT(2)
> +#define LPG_PATTERN_CONFIG_PAUSE_HI BIT(1)
> +#define LPG_PATTERN_CONFIG_PAUSE_LO BIT(0)
Did I miss bits.h inclusion at the beginning of the file?
...
> +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;
> + }
Homegrown duty cycle?
I mean, why simply not to pass the duty cycle in percentage in the first place?
> + duty_us = delay_on * USEC_PER_MSEC;
> + period_us = (delay_on + delay_off) * USEC_PER_MSEC;
> +
> + for (i = 0; i < led->num_channels; i++) {
> + chan = led->channels[i];
> +
> + lpg_calc_freq(chan, period_us);
> + lpg_calc_duty(chan, duty_us);
> +
> + chan->enabled = true;
> + chan->ramp_enabled = false;
> +
> + lpg_apply(chan);
> + }
> +
> + return 0;
> +}
> +#define interpolate(x1, y1, x2, y2, x) \
> + ((y1) + ((y2) - (y1)) * ((x) - (x1)) / ((x2) - (x1)))
Can you rather create a generic one under lib/ or start include/linux/math.h ?
https://elixir.bootlin.com/linux/latest/A/ident/interpolate
...
> +out:
Useless label.
> + return ret;
...
> + ret = of_property_read_u32(np, "color", &color);
> + if (ret < 0 && ret != -EINVAL)
This check is fishy. Either you have optional property or not, in the
latter case return any error code.
> + return ret;
> +
> + chan->color = color;
So, it may be -EINVAL?!
> + ret = of_property_read_u32_array(np, "qcom,dtest", dtest, 2);
> + if (ret < 0 && ret != -EINVAL) {
> + dev_err(lpg->dev, "malformed qcom,dtest of %pOFn\n", np);
> + return ret;
> + } else if (!ret) {
> + chan->dtest_line = dtest[0];
> + chan->dtest_value = dtest[1];
> + }
Ditto.
...
> + ret = of_property_read_u32(np, "color", &color);
> + if (ret < 0 && ret != -EINVAL)
> + return ret;
Ditto.
...
> + size = sizeof(*led) + num_channels * sizeof(struct lpg_channel *);
Use respective helpers from overflow.h.
> + led = devm_kzalloc(lpg->dev, size, GFP_KERNEL);
> + if (!led)
> + return -ENOMEM;
...
> +static const struct of_device_id lpg_of_table[] = {
> + { .compatible = "qcom,pm8916-pwm", .data = &pm8916_pwm_data },
> + { .compatible = "qcom,pm8941-lpg", .data = &pm8941_lpg_data },
> + { .compatible = "qcom,pm8994-lpg", .data = &pm8994_lpg_data },
> + { .compatible = "qcom,pmi8994-lpg", .data = &pmi8994_lpg_data },
> + { .compatible = "qcom,pmi8998-lpg", .data = &pmi8998_lpg_data },
> + {},
No comma needed for terminator lines.
> +};
--
With Best Regards,
Andy Shevchenko
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