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Date: Tue, 12 Jan 2021 10:18:42 +0100
From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Cc: linux-kernel@...r.kernel.org,
Thierry Reding <thierry.reding@...il.com>,
Lee Jones <lee.jones@...aro.org>, f.fainelli@...il.com,
linux-pwm@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com,
linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
wahrenst@....net, linux-input@...r.kernel.org,
dmitry.torokhov@...il.com, gregkh@...uxfoundation.org,
devel@...verdev.osuosl.org, p.zabel@...gutronix.de,
linux-gpio@...r.kernel.org, linus.walleij@...aro.org,
linux-clk@...r.kernel.org, sboyd@...nel.org,
linux-rpi-kernel@...ts.infradead.org, bgolaszewski@...libre.com,
andy.shevchenko@...il.com
Subject: Re: [PATCH v6 11/11] pwm: Add Raspberry Pi Firmware based PWM bus
Hello Nicolas,
On Fri, Dec 11, 2020 at 05:48:00PM +0100, Nicolas Saenz Julienne wrote:
> diff --git a/drivers/pwm/pwm-raspberrypi-poe.c b/drivers/pwm/pwm-raspberrypi-poe.c
> new file mode 100644
> index 000000000000..24b498839fcc
> --- /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@...e.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-poe-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)
I'd like to see this function use the same prefix as the other
functions. I suggest "raspberrypi_pwm_from_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);
Please round up here ...
> + 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);
... and round down here.
Just to be sure: writing RPI_PWM_MAX_DUTY (i.e. 255) yields 100% duty
cycle, right?
> + 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;
Please use tabs for indention. (The general hint is to use checkpatch
which (I hope) tells you about problems like this.)
> +
> + 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;
Please use dev_err_probe to benefit from recording an error message in
this case.
> + 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);
Please use %pe for the error codes (directly or still better by using
dev_err_probe here, too).
> + return ret;
> + }
> +
> + return pwmchip_add(&rpipwm->chip);
> +}
> [...]
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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