u-boot/drivers/pwm/sandbox_pwm.c
Alper Nebi Yasak fefa713b18 video: backlight: Support PWMs without a known period_ns
The PWM device provided by Chrome OS EC doesn't really support anything
other than setting a relative duty cycle. To support it as a backlight,
this patch makes the PWM period optional in the device tree and pretends
the valid brightness range is its period_ns.

Also adds a sandbox test for a PWM channel that has a fixed period,
checking that the resulting duty_cycle matches on a set_config() even if
the requested period_ns can't be set.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2021-04-10 16:07:12 +02:00

120 lines
2.6 KiB
C

// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright (c) 2015 Google, Inc
* Written by Simon Glass <sjg@chromium.org>
*/
#include <common.h>
#include <dm.h>
#include <errno.h>
#include <pwm.h>
#include <asm/test.h>
enum {
NUM_CHANNELS = 3,
};
/**
* struct sandbox_pwm_chan - a sandbox PWM channel
*
* @period_ns: Period of the PWM in nanoseconds
* @duty_ns: Current duty cycle of the PWM in nanoseconds
* @enable: true if the PWM is enabled
* @polarity: true if the PWM polarity is active high
*/
struct sandbox_pwm_chan {
uint period_ns;
uint duty_ns;
bool enable;
bool polarity;
};
struct sandbox_pwm_priv {
struct sandbox_pwm_chan chan[NUM_CHANNELS];
};
int sandbox_pwm_get_config(struct udevice *dev, uint channel, uint *period_nsp,
uint *duty_nsp, bool *enablep, bool *polarityp)
{
struct sandbox_pwm_priv *priv = dev_get_priv(dev);
struct sandbox_pwm_chan *chan;
if (channel >= NUM_CHANNELS)
return -ENOSPC;
chan = &priv->chan[channel];
*period_nsp = chan->period_ns;
*duty_nsp = chan->duty_ns;
*enablep = chan->enable;
*polarityp = chan->polarity;
return 0;
}
static int sandbox_pwm_set_config(struct udevice *dev, uint channel,
uint period_ns, uint duty_ns)
{
struct sandbox_pwm_priv *priv = dev_get_priv(dev);
struct sandbox_pwm_chan *chan;
if (channel >= NUM_CHANNELS)
return -ENOSPC;
chan = &priv->chan[channel];
if (channel == 2) {
/* Pretend to have some fixed period */
chan->period_ns = 4096;
chan->duty_ns = duty_ns * 4096 / period_ns;
} else {
chan->period_ns = period_ns;
chan->duty_ns = duty_ns;
}
return 0;
}
static int sandbox_pwm_set_enable(struct udevice *dev, uint channel,
bool enable)
{
struct sandbox_pwm_priv *priv = dev_get_priv(dev);
struct sandbox_pwm_chan *chan;
if (channel >= NUM_CHANNELS)
return -ENOSPC;
chan = &priv->chan[channel];
chan->enable = enable;
return 0;
}
static int sandbox_pwm_set_invert(struct udevice *dev, uint channel,
bool polarity)
{
struct sandbox_pwm_priv *priv = dev_get_priv(dev);
struct sandbox_pwm_chan *chan;
if (channel >= NUM_CHANNELS)
return -ENOSPC;
chan = &priv->chan[channel];
chan->polarity = polarity;
return 0;
}
static const struct pwm_ops sandbox_pwm_ops = {
.set_config = sandbox_pwm_set_config,
.set_enable = sandbox_pwm_set_enable,
.set_invert = sandbox_pwm_set_invert,
};
static const struct udevice_id sandbox_pwm_ids[] = {
{ .compatible = "sandbox,pwm" },
{ }
};
U_BOOT_DRIVER(warm_pwm_sandbox) = {
.name = "pwm_sandbox",
.id = UCLASS_PWM,
.of_match = sandbox_pwm_ids,
.ops = &sandbox_pwm_ops,
.priv_auto = sizeof(struct sandbox_pwm_priv),
};