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[93.41.3.120]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43d1e2a720dsm69291174f8f.4.2026.04.09.09.13.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Apr 2026 09:13:34 -0700 (PDT) From: Andrea della Porta X-Google-Original-From: Andrea della Porta Date: Thu, 9 Apr 2026 18:16:41 +0200 To: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Cc: Andrea della Porta , linux-pwm@vger.kernel.org, Rob Herring , Krzysztof Kozlowski , Conor Dooley , Florian Fainelli , Broadcom internal kernel review list , devicetree@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Naushir Patuck , Stanimir Varbanov Subject: Re: [PATCH 2/3] pwm: rp1: Add RP1 PWM controller driver Message-ID: References: <28e29fbfc20c0b8a115d006233c2759d8f49e639.1775223441.git.andrea.porta@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260409_091337_629982_89A58E96 X-CRM114-Status: GOOD ( 50.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Uwe, On 23:45 Sun 05 Apr , Uwe Kleine-König wrote: > Hello Andrea, > > On Fri, Apr 03, 2026 at 04:31:55PM +0200, Andrea della Porta wrote: > > From: Naushir Patuck > > > > The Raspberry Pi RP1 southbridge features an embedded PWM > > controller with 4 output channels, alongside an RPM interface > > to read the fan speed on the Raspberry Pi 5. > > > > Add the supporting driver. > > > > Signed-off-by: Naushir Patuck > > Co-developed-by: Stanimir Varbanov > > Signed-off-by: Stanimir Varbanov > > Signed-off-by: Andrea della Porta > > --- > > drivers/pwm/Kconfig | 10 ++ > > drivers/pwm/Makefile | 1 + > > drivers/pwm/pwm-rp1.c | 244 ++++++++++++++++++++++++++++++++++++++++++ > > 3 files changed, 255 insertions(+) > > create mode 100644 drivers/pwm/pwm-rp1.c > > > > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig > > index 6f3147518376a..22e4fc6385da2 100644 > > --- a/drivers/pwm/Kconfig > > +++ b/drivers/pwm/Kconfig > > @@ -625,6 +625,16 @@ config PWM_ROCKCHIP > > Generic PWM framework driver for the PWM controller found on > > Rockchip SoCs. > > > > +config PWM_RP1 > > I prefer PWM_RASPBERRYPI1, or PWM_RASPBERRYPI_RP1 here. Ack. > > > + tristate "RP1 PWM support" > > + depends on MISC_RP1 || COMPILE_TEST > > + depends on HWMON > > + help > > + PWM framework driver for Raspberry Pi RP1 controller > > + > > + To compile this driver as a module, choose M here: the module > > + will be called pwm-rp1. > > + > > config PWM_SAMSUNG > > tristate "Samsung PWM support" > > depends on PLAT_SAMSUNG || ARCH_S5PV210 || ARCH_EXYNOS || COMPILE_TEST > > diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile > > index 0dc0d2b69025d..895a7c42fe9c0 100644 > > --- a/drivers/pwm/Makefile > > +++ b/drivers/pwm/Makefile > > @@ -56,6 +56,7 @@ obj-$(CONFIG_PWM_RENESAS_RZG2L_GPT) += pwm-rzg2l-gpt.o > > obj-$(CONFIG_PWM_RENESAS_RZ_MTU3) += pwm-rz-mtu3.o > > obj-$(CONFIG_PWM_RENESAS_TPU) += pwm-renesas-tpu.o > > obj-$(CONFIG_PWM_ROCKCHIP) += pwm-rockchip.o > > +obj-$(CONFIG_PWM_RP1) += pwm-rp1.o > > obj-$(CONFIG_PWM_SAMSUNG) += pwm-samsung.o > > obj-$(CONFIG_PWM_SIFIVE) += pwm-sifive.o > > obj-$(CONFIG_PWM_SL28CPLD) += pwm-sl28cpld.o > > diff --git a/drivers/pwm/pwm-rp1.c b/drivers/pwm/pwm-rp1.c > > new file mode 100644 > > index 0000000000000..0a1c1c1dd27e9 > > --- /dev/null > > +++ b/drivers/pwm/pwm-rp1.c > > @@ -0,0 +1,244 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +/* > > + * pwm-rp1.c > > + * > > + * Raspberry Pi RP1 PWM. > > + * > > + * Copyright © 2026 Raspberry Pi Ltd. > > + * > > + * Author: Naushir Patuck (naush@raspberrypi.com) > > + * > > + * Based on the pwm-bcm2835 driver by: > > + * Bart Tanghe > > + */ > > Please add a paragraph here named "Limitations" in the same format as > several other drivers describing how the driver behaves on disable and > configuration changes (can glitches occur? Is the currently running > period completed or aborted?) Ack. > > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > + > > +#define PWM_GLOBAL_CTRL 0x000 > > +#define PWM_CHANNEL_CTRL(x) (0x014 + ((x) * 0x10)) > > +#define PWM_RANGE(x) (0x018 + ((x) * 0x10)) > > +#define PWM_PHASE(x) (0x01C + ((x) * 0x10)) > > +#define PWM_DUTY(x) (0x020 + ((x) * 0x10)) > > + > > +/* 8:FIFO_POP_MASK + 0:Trailing edge M/S modulation */ > > +#define PWM_CHANNEL_DEFAULT (BIT(8) + BIT(0)) > > +#define PWM_CHANNEL_ENABLE(x) BIT(x) > > +#define PWM_POLARITY BIT(3) > > +#define SET_UPDATE BIT(31) > > +#define PWM_MODE_MASK GENMASK(1, 0) > > + > > +#define NUM_PWMS 4 > > Please prefix all #defines by something driver specific (e.g. RP1_PWM_). Ack. > > > + > > +struct rp1_pwm { > > + void __iomem *base; > > + struct clk *clk; > > +}; > > + > > +static const struct hwmon_channel_info * const rp1_fan_hwmon_info[] = { > > + HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT), > > + NULL > > +}; > > + > > +static umode_t rp1_fan_hwmon_is_visible(const void *data, enum hwmon_sensor_types type, > > + u32 attr, int channel) > > +{ > > + umode_t mode = 0; > > + > > + if (type == hwmon_fan && attr == hwmon_fan_input) > > + mode = 0444; > > + > > + return mode; > > +} > > + > > +static int rp1_fan_hwmon_read(struct device *dev, enum hwmon_sensor_types type, > > + u32 attr, int channel, long *val) > > +{ > > + struct rp1_pwm *rp1 = dev_get_drvdata(dev); > > + > > + if (type != hwmon_fan || attr != hwmon_fan_input) > > + return -EOPNOTSUPP; > > + > > + *val = readl(rp1->base + PWM_PHASE(2)); > > + > > + return 0; > > +} > > I don't like having hwmon bits in pwm drivers. Is the PWM only usable > for a fan? I guess the hwmon parts should be dropped and a pwm-fan > defined in dt. The pwm-fan generic driver expects an interrupt to count the RPM, while on RP1 this data is passed via a register filled by the RP1 fw running on the internal core. Instead of changing the generic pwm-fan driver, I'll add a syscon to export this register which will be read by a new device/driver registering an hwmon device. > > > +static const struct hwmon_ops rp1_fan_hwmon_ops = { > > + .is_visible = rp1_fan_hwmon_is_visible, > > + .read = rp1_fan_hwmon_read, > > +}; > > + > > +static const struct hwmon_chip_info rp1_fan_hwmon_chip_info = { > > + .ops = &rp1_fan_hwmon_ops, > > + .info = rp1_fan_hwmon_info, > > +}; > > + > > +static void rp1_pwm_apply_config(struct pwm_chip *chip, struct pwm_device *pwm) > > +{ > > + struct rp1_pwm *rp1 = pwmchip_get_drvdata(chip); > > + u32 value; > > + > > + value = readl(rp1->base + PWM_GLOBAL_CTRL); > > + value |= SET_UPDATE; > > + writel(value, rp1->base + PWM_GLOBAL_CTRL); > > +} > > + > > +static int rp1_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm) > > +{ > > + struct rp1_pwm *rp1 = pwmchip_get_drvdata(chip); > > + > > + writel(PWM_CHANNEL_DEFAULT, rp1->base + PWM_CHANNEL_CTRL(pwm->hwpwm)); > > Please add a comment about what this does. Ack. > > > + return 0; > > +} > > + > > +static void rp1_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm) > > +{ > > + struct rp1_pwm *rp1 = pwmchip_get_drvdata(chip); > > + u32 value; > > + > > + value = readl(rp1->base + PWM_CHANNEL_CTRL(pwm->hwpwm)); > > + value &= ~PWM_MODE_MASK; > > + writel(value, rp1->base + PWM_CHANNEL_CTRL(pwm->hwpwm)); > > + > > + rp1_pwm_apply_config(chip, pwm); > > What is the purpose of this call? To update the configuration on the next PWM strobe in order to avoid glitches. I'll add a short comment in the code. > > > +} > > + > > +static int rp1_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, > > + const struct pwm_state *state) > > +{ > > + struct rp1_pwm *rp1 = pwmchip_get_drvdata(chip); > > + unsigned long clk_rate = clk_get_rate(rp1->clk); > > + unsigned long clk_period; > > + u32 value; > > + > > + if (!clk_rate) { > > + dev_err(&chip->dev, "failed to get clock rate\n"); > > + return -EINVAL; > > + } > > + > > + /* set period and duty cycle */ > > + clk_period = DIV_ROUND_CLOSEST(NSEC_PER_SEC, clk_rate); > > DIV_ROUND_CLOSEST is wrong here. (I don't go into details as .apply() > should be dropped.) Ack. > > > + writel(DIV_ROUND_CLOSEST(state->duty_cycle, clk_period), > > Dividing by the result of a division loses precision. > > > + rp1->base + PWM_DUTY(pwm->hwpwm)); > > + > > + writel(DIV_ROUND_CLOSEST(state->period, clk_period), > > + rp1->base + PWM_RANGE(pwm->hwpwm)); > > + > > + /* set polarity */ > > + value = readl(rp1->base + PWM_CHANNEL_CTRL(pwm->hwpwm)); > > + if (state->polarity == PWM_POLARITY_NORMAL) > > + value &= ~PWM_POLARITY; > > + else > > + value |= PWM_POLARITY; > > + writel(value, rp1->base + PWM_CHANNEL_CTRL(pwm->hwpwm)); > > + > > + /* enable/disable */ > > + value = readl(rp1->base + PWM_GLOBAL_CTRL); > > + if (state->enabled) > > + value |= PWM_CHANNEL_ENABLE(pwm->hwpwm); > > + else > > + value &= ~PWM_CHANNEL_ENABLE(pwm->hwpwm); > > + writel(value, rp1->base + PWM_GLOBAL_CTRL); > > + > > + rp1_pwm_apply_config(chip, pwm); > > + > > + return 0; > > +} > > + > > +static const struct pwm_ops rp1_pwm_ops = { > > + .request = rp1_pwm_request, > > + .free = rp1_pwm_free, > > + .apply = rp1_pwm_apply, > > Please implement the waveform callbacks instead of .apply(). Ack. > > > +}; > > + > > +static int rp1_pwm_probe(struct platform_device *pdev) > > +{ > > + struct device *dev = &pdev->dev; > > + struct device *hwmon_dev; > > + struct pwm_chip *chip; > > + struct rp1_pwm *rp1; > > + int ret; > > + > > + chip = devm_pwmchip_alloc(dev, NUM_PWMS, sizeof(*rp1)); > > + if (IS_ERR(chip)) > > + return PTR_ERR(chip); > > + > > + rp1 = pwmchip_get_drvdata(chip); > > + > > + rp1->base = devm_platform_ioremap_resource(pdev, 0); > > + if (IS_ERR(rp1->base)) > > + return PTR_ERR(rp1->base); > > + > > + rp1->clk = devm_clk_get_enabled(dev, NULL); > > + if (IS_ERR(rp1->clk)) > > + return dev_err_probe(dev, PTR_ERR(rp1->clk), "clock not found\n"); > > Please start error messages with a capital letter. Ack. > > > + > > + ret = devm_clk_rate_exclusive_get(dev, rp1->clk); > > After this call you can determine the rate just once and fail if it's == > 0. Ack. > > > + if (ret) > > + return dev_err_probe(dev, ret, "fail to get exclusive rate\n"); > > + > > + chip->ops = &rp1_pwm_ops; > > + > > + platform_set_drvdata(pdev, chip); > > + > > + ret = devm_pwmchip_add(dev, chip); > > + if (ret) > > + return dev_err_probe(dev, ret, "failed to register PWM chip\n"); > > + > > + hwmon_dev = devm_hwmon_device_register_with_info(dev, "rp1_fan_tach", rp1, > > + &rp1_fan_hwmon_chip_info, > > + NULL); > > + > > + if (IS_ERR(hwmon_dev)) > > + return dev_err_probe(dev, PTR_ERR(hwmon_dev), > > + "failed to register hwmon fan device\n"); > > + > > + return 0; > > +} > > + > > +static int rp1_pwm_suspend(struct device *dev) > > +{ > > + struct rp1_pwm *rp1 = dev_get_drvdata(dev); > > + > > + clk_disable_unprepare(rp1->clk); > > + > > + return 0; > > +} > > + > > +static int rp1_pwm_resume(struct device *dev) > > +{ > > + struct rp1_pwm *rp1 = dev_get_drvdata(dev); > > + > > + return clk_prepare_enable(rp1->clk); > > Hmm, if this fails and then the driver is unbound, the clk operations > are not balanced. I'll add some flags to check if the clock is really enabled or not. Regards, Andrea > > > +} > > + > > +static DEFINE_SIMPLE_DEV_PM_OPS(rp1_pwm_pm_ops, rp1_pwm_suspend, rp1_pwm_resume); > > + > > +static const struct of_device_id rp1_pwm_of_match[] = { > > + { .compatible = "raspberrypi,rp1-pwm" }, > > + { /* sentinel */ } > > +}; > > +MODULE_DEVICE_TABLE(of, rp1_pwm_of_match); > > + > > +static struct platform_driver rp1_pwm_driver = { > > + .probe = rp1_pwm_probe, > > + .driver = { > > + .name = "rp1-pwm", > > + .of_match_table = rp1_pwm_of_match, > > + .pm = pm_ptr(&rp1_pwm_pm_ops), > > + }, > > +}; > > +module_platform_driver(rp1_pwm_driver); > > + > > +MODULE_DESCRIPTION("RP1 PWM driver"); > > +MODULE_AUTHOR("Naushir Patuck "); > > +MODULE_LICENSE("GPL"); > > -- > > 2.35.3 > > > > Best regards > Uwe