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![Nicolas Saenz Julienne](/assets/img/avatar_default.png)
Adds support to control the PWM bus available in official Raspberry Pi PoE HAT. Only RPi's co-processor has access to it, so commands have to be sent through RPi's firmware mailbox interface. Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Acked-by: Thierry Reding <thierry.reding@gmail.com>
206 lines
5 KiB
C
206 lines
5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright 2021 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
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* For more information on Raspberry Pi's PoE hat see:
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* https://www.raspberrypi.org/products/poe-hat/
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*
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* Limitations:
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* - No disable bit, so a disabled PWM is simulated by duty_cycle 0
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* - Only normal polarity
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* - Fixed 12.5 kHz period
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*
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* The current period is completed when HW is reconfigured.
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*/
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#include <linux/module.h>
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#include <linux/of.h>
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#include <linux/platform_device.h>
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#include <linux/pwm.h>
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#include <soc/bcm2835/raspberrypi-firmware.h>
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#include <dt-bindings/pwm/raspberrypi,firmware-poe-pwm.h>
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#define RPI_PWM_MAX_DUTY 255
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#define RPI_PWM_PERIOD_NS 80000 /* 12.5 kHz */
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#define RPI_PWM_CUR_DUTY_REG 0x0
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struct raspberrypi_pwm {
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struct rpi_firmware *firmware;
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struct pwm_chip chip;
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unsigned int duty_cycle;
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};
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struct raspberrypi_pwm_prop {
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__le32 reg;
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__le32 val;
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__le32 ret;
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} __packed;
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static inline
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struct raspberrypi_pwm *raspberrypi_pwm_from_chip(struct pwm_chip *chip)
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{
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return container_of(chip, struct raspberrypi_pwm, chip);
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}
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static int raspberrypi_pwm_set_property(struct rpi_firmware *firmware,
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u32 reg, u32 val)
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{
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struct raspberrypi_pwm_prop msg = {
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.reg = cpu_to_le32(reg),
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.val = cpu_to_le32(val),
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};
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int ret;
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ret = rpi_firmware_property(firmware, RPI_FIRMWARE_SET_POE_HAT_VAL,
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&msg, sizeof(msg));
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if (ret)
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return ret;
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if (msg.ret)
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return -EIO;
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return 0;
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}
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static int raspberrypi_pwm_get_property(struct rpi_firmware *firmware,
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u32 reg, u32 *val)
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{
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struct raspberrypi_pwm_prop msg = {
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.reg = reg
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};
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int ret;
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ret = rpi_firmware_property(firmware, RPI_FIRMWARE_GET_POE_HAT_VAL,
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&msg, sizeof(msg));
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if (ret)
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return ret;
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if (msg.ret)
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return -EIO;
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*val = le32_to_cpu(msg.val);
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return 0;
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}
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static void raspberrypi_pwm_get_state(struct pwm_chip *chip,
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struct pwm_device *pwm,
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struct pwm_state *state)
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{
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struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);
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state->period = RPI_PWM_PERIOD_NS;
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state->duty_cycle = DIV_ROUND_UP(rpipwm->duty_cycle * RPI_PWM_PERIOD_NS,
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RPI_PWM_MAX_DUTY);
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state->enabled = !!(rpipwm->duty_cycle);
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state->polarity = PWM_POLARITY_NORMAL;
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}
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static int raspberrypi_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
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const struct pwm_state *state)
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{
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struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);
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unsigned int duty_cycle;
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int ret;
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if (state->period < RPI_PWM_PERIOD_NS ||
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state->polarity != PWM_POLARITY_NORMAL)
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return -EINVAL;
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if (!state->enabled)
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duty_cycle = 0;
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else if (state->duty_cycle < RPI_PWM_PERIOD_NS)
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duty_cycle = DIV_ROUND_DOWN_ULL(state->duty_cycle * RPI_PWM_MAX_DUTY,
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RPI_PWM_PERIOD_NS);
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else
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duty_cycle = RPI_PWM_MAX_DUTY;
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if (duty_cycle == rpipwm->duty_cycle)
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return 0;
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ret = raspberrypi_pwm_set_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
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duty_cycle);
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if (ret) {
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dev_err(chip->dev, "Failed to set duty cycle: %pe\n",
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ERR_PTR(ret));
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return ret;
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}
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rpipwm->duty_cycle = duty_cycle;
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return 0;
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}
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static const struct pwm_ops raspberrypi_pwm_ops = {
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.get_state = raspberrypi_pwm_get_state,
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.apply = raspberrypi_pwm_apply,
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.owner = THIS_MODULE,
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};
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static int raspberrypi_pwm_probe(struct platform_device *pdev)
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{
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struct device_node *firmware_node;
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struct device *dev = &pdev->dev;
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struct rpi_firmware *firmware;
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struct raspberrypi_pwm *rpipwm;
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int ret;
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firmware_node = of_get_parent(dev->of_node);
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if (!firmware_node) {
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dev_err(dev, "Missing firmware node\n");
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return -ENOENT;
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}
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firmware = devm_rpi_firmware_get(&pdev->dev, firmware_node);
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of_node_put(firmware_node);
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if (!firmware)
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return dev_err_probe(dev, -EPROBE_DEFER,
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"Failed to get firmware handle\n");
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rpipwm = devm_kzalloc(&pdev->dev, sizeof(*rpipwm), GFP_KERNEL);
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if (!rpipwm)
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return -ENOMEM;
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rpipwm->firmware = firmware;
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rpipwm->chip.dev = dev;
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rpipwm->chip.ops = &raspberrypi_pwm_ops;
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rpipwm->chip.base = -1;
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rpipwm->chip.npwm = RASPBERRYPI_FIRMWARE_PWM_NUM;
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platform_set_drvdata(pdev, rpipwm);
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ret = raspberrypi_pwm_get_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
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&rpipwm->duty_cycle);
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if (ret) {
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dev_err(dev, "Failed to get duty cycle: %pe\n", ERR_PTR(ret));
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return ret;
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}
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return pwmchip_add(&rpipwm->chip);
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}
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static int raspberrypi_pwm_remove(struct platform_device *pdev)
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{
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struct raspberrypi_pwm *rpipwm = platform_get_drvdata(pdev);
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return pwmchip_remove(&rpipwm->chip);
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}
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static const struct of_device_id raspberrypi_pwm_of_match[] = {
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{ .compatible = "raspberrypi,firmware-poe-pwm", },
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{ }
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};
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MODULE_DEVICE_TABLE(of, raspberrypi_pwm_of_match);
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static struct platform_driver raspberrypi_pwm_driver = {
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.driver = {
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.name = "raspberrypi-poe-pwm",
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.of_match_table = raspberrypi_pwm_of_match,
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},
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.probe = raspberrypi_pwm_probe,
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.remove = raspberrypi_pwm_remove,
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};
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module_platform_driver(raspberrypi_pwm_driver);
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MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
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MODULE_DESCRIPTION("Raspberry Pi Firmware Based PWM Bus Driver");
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MODULE_LICENSE("GPL v2");
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