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    Subject[PATCH v4 11/11] pwm: Add Raspberry Pi Firmware based PWM bus
    Date
    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>
    ---

    Changes since v2:
    - Use devm_rpi_firmware_get()
    - Rename driver
    - Small cleanups

    Changes since v1:
    - Use default pwm bindings and get rid of xlate() function
    - Correct spelling errors
    - Correct apply() function
    - Round values
    - Fix divisions in arm32 mode
    - Small cleanups

    drivers/pwm/Kconfig | 9 ++
    drivers/pwm/Makefile | 1 +
    drivers/pwm/pwm-raspberrypi-poe.c | 216 ++++++++++++++++++++++++++++++
    3 files changed, 226 insertions(+)
    create mode 100644 drivers/pwm/pwm-raspberrypi-poe.c

    diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
    index b2a87fd7e8fb..3445984a5a50 100644
    --- a/drivers/pwm/Kconfig
    +++ b/drivers/pwm/Kconfig
    @@ -409,6 +409,15 @@ config PWM_PXA
    To compile this driver as a module, choose M here: the module
    will be called pwm-pxa.

    +config PWM_RASPBERRYPI_POE
    + tristate "Raspberry Pi Firwmware PoE Hat PWM support"
    + # Make sure not 'y' when RASPBERRYPI_FIRMWARE is 'm'. This can only
    + # happen when COMPILE_TEST=y, hence the added !RASPBERRYPI_FIRMWARE.
    + depends on RASPBERRYPI_FIRMWARE || (COMPILE_TEST && !RASPBERRYPI_FIRMWARE)
    + help
    + Enable Raspberry Pi firmware controller PWM bus used to control the
    + official RPI PoE hat
    +
    config PWM_RCAR
    tristate "Renesas R-Car PWM support"
    depends on ARCH_RENESAS || COMPILE_TEST
    diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
    index 18b89d7fd092..ed28d7bd4c64 100644
    --- a/drivers/pwm/Makefile
    +++ b/drivers/pwm/Makefile
    @@ -38,6 +38,7 @@ obj-$(CONFIG_PWM_MXS) += pwm-mxs.o
    obj-$(CONFIG_PWM_OMAP_DMTIMER) += pwm-omap-dmtimer.o
    obj-$(CONFIG_PWM_PCA9685) += pwm-pca9685.o
    obj-$(CONFIG_PWM_PXA) += pwm-pxa.o
    +obj-$(CONFIG_PWM_RASPBERRYPI_POE) += pwm-raspberrypi-poe.o
    obj-$(CONFIG_PWM_RCAR) += pwm-rcar.o
    obj-$(CONFIG_PWM_RENESAS_TPU) += pwm-renesas-tpu.o
    obj-$(CONFIG_PWM_ROCKCHIP) += pwm-rockchip.o
    diff --git a/drivers/pwm/pwm-raspberrypi-poe.c b/drivers/pwm/pwm-raspberrypi-poe.c
    new file mode 100644
    index 000000000000..91cd826a36f3
    --- /dev/null
    +++ b/drivers/pwm/pwm-raspberrypi-poe.c
    @@ -0,0 +1,216 @@
    +// SPDX-License-Identifier: GPL-2.0
    +/*
    + * Copyright 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
    + * For more information on Raspberry Pi's PoE hat see:
    + * https://www.raspberrypi.org/products/poe-hat/
    + *
    + * Limitations:
    + * - No disable bit, so a disabled PWM is simulated by duty_cycle 0
    + * - Only normal polarity
    + * - Fixed 12.5 kHz period
    + *
    + * The current period is completed when HW is reconfigured.
    + */
    +
    +#include <linux/module.h>
    +#include <linux/of.h>
    +#include <linux/platform_device.h>
    +#include <linux/pwm.h>
    +
    +#include <soc/bcm2835/raspberrypi-firmware.h>
    +#include <dt-bindings/pwm/raspberrypi,firmware-pwm.h>
    +
    +#define RPI_PWM_MAX_DUTY 255
    +#define RPI_PWM_PERIOD_NS 80000 /* 12.5 kHz */
    +
    +#define RPI_PWM_CUR_DUTY_REG 0x0
    +#define RPI_PWM_DEF_DUTY_REG 0x1
    +
    +struct raspberrypi_pwm {
    + struct rpi_firmware *firmware;
    + struct pwm_chip chip;
    + unsigned int duty_cycle;
    +};
    +
    +struct raspberrypi_pwm_prop {
    + __le32 reg;
    + __le32 val;
    + __le32 ret;
    +} __packed;
    +
    +static inline struct raspberrypi_pwm *to_raspberrypi_pwm(struct pwm_chip *chip)
    +{
    + return container_of(chip, struct raspberrypi_pwm, chip);
    +}
    +
    +static int raspberrypi_pwm_set_property(struct rpi_firmware *firmware,
    + u32 reg, u32 val)
    +{
    + struct raspberrypi_pwm_prop msg = {
    + .reg = cpu_to_le32(reg),
    + .val = cpu_to_le32(val),
    + };
    + int ret;
    +
    + ret = rpi_firmware_property(firmware, RPI_FIRMWARE_SET_POE_HAT_VAL,
    + &msg, sizeof(msg));
    + if (ret)
    + return ret;
    + if (msg.ret)
    + return -EIO;
    +
    + return 0;
    +}
    +
    +static int raspberrypi_pwm_get_property(struct rpi_firmware *firmware,
    + u32 reg, u32 *val)
    +{
    + struct raspberrypi_pwm_prop msg = {
    + .reg = reg
    + };
    + int ret;
    +
    + ret = rpi_firmware_property(firmware, RPI_FIRMWARE_GET_POE_HAT_VAL,
    + &msg, sizeof(msg));
    + if (ret)
    + return ret;
    + if (msg.ret)
    + return -EIO;
    +
    + *val = le32_to_cpu(msg.val);
    +
    + return 0;
    +}
    +
    +static void raspberrypi_pwm_get_state(struct pwm_chip *chip,
    + struct pwm_device *pwm,
    + struct pwm_state *state)
    +{
    + struct raspberrypi_pwm *rpipwm = to_raspberrypi_pwm(chip);
    +
    + state->period = RPI_PWM_PERIOD_NS;
    + state->duty_cycle = DIV_ROUND_CLOSEST(rpipwm->duty_cycle * RPI_PWM_PERIOD_NS,
    + RPI_PWM_MAX_DUTY);
    + state->enabled = !!(rpipwm->duty_cycle);
    + state->polarity = PWM_POLARITY_NORMAL;
    +}
    +
    +static int raspberrypi_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
    + const struct pwm_state *state)
    +{
    + struct raspberrypi_pwm *rpipwm = to_raspberrypi_pwm(chip);
    + unsigned int duty_cycle;
    + int ret;
    +
    + if (state->period < RPI_PWM_PERIOD_NS ||
    + state->polarity != PWM_POLARITY_NORMAL)
    + return -EINVAL;
    +
    + if (!state->enabled)
    + duty_cycle = 0;
    + else if (state->duty_cycle < RPI_PWM_PERIOD_NS)
    + duty_cycle = DIV_ROUND_CLOSEST_ULL(state->duty_cycle * RPI_PWM_MAX_DUTY,
    + RPI_PWM_PERIOD_NS);
    + else
    + duty_cycle = RPI_PWM_MAX_DUTY;
    +
    + if (duty_cycle == rpipwm->duty_cycle)
    + return 0;
    +
    + ret = raspberrypi_pwm_set_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
    + duty_cycle);
    + if (ret) {
    + dev_err(chip->dev, "Failed to set duty cycle: %d\n", ret);
    + return ret;
    + }
    +
    + /*
    + * This sets the default duty cycle after resetting the board, we
    + * updated it every time to mimic Raspberry Pi's downstream's driver
    + * behaviour.
    + */
    + ret = raspberrypi_pwm_set_property(rpipwm->firmware, RPI_PWM_DEF_DUTY_REG,
    + duty_cycle);
    + if (ret) {
    + dev_err(chip->dev, "Failed to set default duty cycle: %d\n", ret);
    + return ret;
    + }
    +
    + rpipwm->duty_cycle = duty_cycle;
    +
    + return 0;
    +}
    +
    +static const struct pwm_ops raspberrypi_pwm_ops = {
    + .get_state = raspberrypi_pwm_get_state,
    + .apply = raspberrypi_pwm_apply,
    + .owner = THIS_MODULE,
    +};
    +
    +static int raspberrypi_pwm_probe(struct platform_device *pdev)
    +{
    + struct device_node *firmware_node;
    + struct device *dev = &pdev->dev;
    + struct rpi_firmware *firmware;
    + struct raspberrypi_pwm *rpipwm;
    + int ret;
    +
    + firmware_node = of_get_parent(dev->of_node);
    + if (!firmware_node) {
    + dev_err(dev, "Missing firmware node\n");
    + return -ENOENT;
    + }
    +
    + firmware = devm_rpi_firmware_get(&pdev->dev, firmware_node);
    + of_node_put(firmware_node);
    + if (!firmware)
    + return -EPROBE_DEFER;
    +
    + rpipwm = devm_kzalloc(&pdev->dev, sizeof(*rpipwm), GFP_KERNEL);
    + if (!rpipwm)
    + return -ENOMEM;
    +
    + rpipwm->firmware = firmware;
    + rpipwm->chip.dev = dev;
    + rpipwm->chip.ops = &raspberrypi_pwm_ops;
    + rpipwm->chip.base = -1;
    + rpipwm->chip.npwm = RASPBERRYPI_FIRMWARE_PWM_NUM;
    +
    + platform_set_drvdata(pdev, rpipwm);
    +
    + ret = raspberrypi_pwm_get_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
    + &rpipwm->duty_cycle);
    + if (ret) {
    + dev_err(dev, "Failed to get duty cycle: %d\n", ret);
    + return ret;
    + }
    +
    + return pwmchip_add(&rpipwm->chip);
    +}
    +
    +static int raspberrypi_pwm_remove(struct platform_device *pdev)
    +{
    + struct raspberrypi_pwm *rpipwm = platform_get_drvdata(pdev);
    +
    + return pwmchip_remove(&rpipwm->chip);
    +}
    +
    +static const struct of_device_id raspberrypi_pwm_of_match[] = {
    + { .compatible = "raspberrypi,firmware-pwm", },
    + { }
    +};
    +MODULE_DEVICE_TABLE(of, raspberrypi_pwm_of_match);
    +
    +static struct platform_driver raspberrypi_pwm_driver = {
    + .driver = {
    + .name = "raspberrypi-pwm",
    + .of_match_table = raspberrypi_pwm_of_match,
    + },
    + .probe = raspberrypi_pwm_probe,
    + .remove = raspberrypi_pwm_remove,
    +};
    +module_platform_driver(raspberrypi_pwm_driver);
    +
    +MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
    +MODULE_DESCRIPTION("Raspberry Pi Firwmare Based PWM Bus Driver");
    +MODULE_LICENSE("GPL v2");
    --
    2.29.2
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      Last update: 2020-11-12 17:46    [W:3.204 / U:0.104 seconds]
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