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leds: qcom-lpg: Require pattern to follow documentation

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The leds-trigger-pattern documentation describes how the brightness of
the LED should transition linearly from one brightness value to the
next, over the given delta_t.

But the pattern engine in the Qualcomm LPG hardware only supports
holding the brightness for each entry for the period.
This subset of patterns can be represented in the leds-trigger-pattern
by injecting zero-time transitions after each entry in the pattern,
resulting in a pattern that pattern that can be rendered by the LPG.

Rework LPG pattern interface to require these zero-time transitions, to
make it comply with this subset of patterns and reject the patterns it
can't render.

Fixes: 24e2d05d1b ("leds: Add driver for Qualcomm LPG")
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>
This commit is contained in:
Bjorn Andersson 2022-05-23 16:37:19 -07:00 committed by Pavel Machek
parent 73bce575ed
commit e98a860f65
2 changed files with 43 additions and 8 deletions
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8
Documentation/leds/leds-qcom-lpg.rst
View File

@ -35,11 +35,13 @@ Specify a hardware pattern for a Qualcomm LPG LED.
The pattern is a series of brightness and hold-time pairs, with the hold-time
expressed in milliseconds. The hold time is a property of the pattern and must
therefor be identical for each element in the pattern (except for the pauses
described below).
described below). As the LPG hardware is not able to perform the linear
transitions expected by the leds-trigger-pattern format, each entry in the
pattern must be followed a zero-length entry of the same brightness.
Simple pattern::
"255 500 0 500"
"255 500 255 0 0 500 0 0"
^
|
@ -54,7 +56,7 @@ in the pattern, the so called "low pause" and "high pause".
Low-pause pattern::
"255 1000 0 500 255 500 0 500"
"255 1000 255 0 0 500 0 0 255 500 255 0 0 500 0 0"
^
|

43
drivers/leds/rgb/leds-qcom-lpg.c
View File

@ -704,11 +704,12 @@ static int lpg_blink_mc_set(struct led_classdev *cdev,
return ret;
}
static int lpg_pattern_set(struct lpg_led *led, struct led_pattern *pattern,
static int lpg_pattern_set(struct lpg_led *led, struct led_pattern *led_pattern,
u32 len, int repeat)
{
struct lpg_channel *chan;
struct lpg *lpg = led->lpg;
struct led_pattern *pattern;
unsigned int brightness_a;
unsigned int brightness_b;
unsigned int actual_len;
@ -719,18 +720,48 @@ static int lpg_pattern_set(struct lpg_led *led, struct led_pattern *pattern,
unsigned int hi_idx;
unsigned int i;
bool ping_pong = true;
int ret;
int ret = -EINVAL;
/* Hardware only support oneshot or indefinite loops */
if (repeat != -1 && repeat != 1)
return -EINVAL;
/*
* The standardized leds-trigger-pattern format defines that the
* brightness of the LED follows a linear transition from one entry
* in the pattern to the next, over the given delta_t time. It
* describes that the way to perform instant transitions a zero-length
* entry should be added following a pattern entry.
*
* The LPG hardware is only able to perform the latter (no linear
* transitions), so require each entry in the pattern to be followed by
* a zero-length transition.
*/
if (len % 2)
return -EINVAL;
pattern = kcalloc(len / 2, sizeof(*pattern), GFP_KERNEL);
if (!pattern)
return -ENOMEM;
for (i = 0; i < len; i += 2) {
if (led_pattern[i].brightness != led_pattern[i + 1].brightness)
goto out_free_pattern;
if (led_pattern[i + 1].delta_t != 0)
goto out_free_pattern;
pattern[i / 2].brightness = led_pattern[i].brightness;
pattern[i / 2].delta_t = led_pattern[i].delta_t;
}
len /= 2;
/*
* Specifying a pattern of length 1 causes the hardware to iterate
* through the entire LUT, so prohibit this.
*/
if (len < 2)
return -EINVAL;
goto out_free_pattern;
/*
* The LPG plays patterns with at a fixed pace, a "low pause" can be
@ -781,13 +812,13 @@ static int lpg_pattern_set(struct lpg_led *led, struct led_pattern *pattern,
* specify hi pause. Reject other variations.
*/
if (i != actual_len - 1)
return -EINVAL;
goto out_free_pattern;
}
}
/* LPG_RAMP_DURATION_REG is a 9bit */
if (delta_t >= BIT(9))
return -EINVAL;
goto out_free_pattern;
/* Find "low pause" and "high pause" in the pattern */
lo_pause = pattern[0].delta_t;
@ -814,6 +845,8 @@ static int lpg_pattern_set(struct lpg_led *led, struct led_pattern *pattern,
out_unlock:
mutex_unlock(&lpg->lock);
out_free_pattern:
kfree(pattern);
return ret;
}