Re: [PATCH v3 2/5] mfd: Add Rockchip mfpwm driver

Lee Jones
2025-11-03T15:26:14Z

On Tue, 28 Oct 2025, Johan Jonker wrote:

>
>
> On 10/27/25 18:11, Nicolas Frattaroli wrote:
> > With the Rockchip RK3576, the PWM IP used by Rockchip has changed
> > substantially. Looking at both the downstream pwm-rockchip driver as
> > well as the mainline pwm-rockchip driver made it clear that with all its
> > additional features and its differences from previous IP revisions, it
> > is best supported in a new driver.
> >
> > This brings us to the question as to what such a new driver should be.
> > To me, it soon became clear that it should actually be several new
> > drivers, most prominently when Uwe Kleine-König let me know that I
> > should not implement the pwm subsystem's capture callback, but instead
> > write a counter driver for this functionality.
> >
> > Combined with the other as-of-yet unimplemented functionality of this
> > new IP, it became apparent that it needs to be spread across several
> > subsystems.
> >
> > For this reason, we add a new MFD core driver, called mfpwm (short for
> > "Multi-function PWM"). This "parent" driver makes sure that only one
> > device function driver is using the device at a time, and is in charge
> > of registering the MFD cell devices for the individual device functions
> > offered by the device.
> >
> > An acquire/release pattern is used to guarantee that device function
> > drivers don't step on each other's toes.
> >
> > Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
> > ---
> > MAINTAINERS | 2 +
> > drivers/mfd/Kconfig | 15 ++
> > drivers/mfd/Makefile | 1 +
> > drivers/mfd/rockchip-mfpwm.c | 340 +++++++++++++++++++++++++++
> > include/linux/mfd/rockchip-mfpwm.h | 454 +++++++++++++++++++++++++++++++++++++
> > 5 files changed, 812 insertions(+)
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index baecabab35a2..8f3235ba825e 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -22372,6 +22372,8 @@ L: linux-rockchip@lists.infradead.org
> > L: linux-pwm@vger.kernel.org
> > S: Maintained
>
> > F: Documentation/devicetree/bindings/pwm/rockchip,rk3576-pwm.yaml
>
> A question not so much for Nicolas specific:
> The yaml documents already have a 'maintainers' entry.
> However MAINTAINERS is full yaml entries.
> Could someone explain why we still need dual registration?
>
> maintainers:
> - Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
>
> > +F: drivers/soc/rockchip/mfpwm.c
> > +F: include/soc/rockchip/mfpwm.h
>
> different file name and location?
>
> drivers/mfd/rockchip-mfpwm.c | 340 +++++++++++++++++++++++++++
> include/linux/mfd/rockchip-mfpwm.h | 454 +++++++++++++++++++++++++++++++++++++
>
>
> >
> > ROCKCHIP RK3568 RANDOM NUMBER GENERATOR SUPPORT
> > M: Daniel Golle <daniel@makrotopia.org>
> > diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> > index dbeac6825a10..8b3a3160fbdf 100644
> > --- a/drivers/mfd/Kconfig
> > +++ b/drivers/mfd/Kconfig
> > @@ -1367,6 +1367,21 @@ config MFD_RC5T583
> > Additional drivers must be enabled in order to use the
> > different functionality of the device.
> >
> > +config MFD_ROCKCHIP_MFPWM
> > + tristate "Rockchip multi-function PWM controller"
> > + depends on OF
> > + depends on HAS_IOMEM
> > + depends on COMMON_CLK
> > + select MFD_CORE
> > + help
> > + Some Rockchip SoCs, such as the RK3576, use a PWM controller that has
> > + several different functions, such as generating PWM waveforms but also
> > + counting waveforms.
> > +
> > + This driver manages the overall device, and selects between different
> > + functionalities at runtime as needed. Drivers for them are implemented
> > + in their respective subsystems.
> > +
> > config MFD_RK8XX
> > tristate
> > select MFD_CORE
> > diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> > index e75e8045c28a..ebadbaea9e4a 100644
> > --- a/drivers/mfd/Makefile
> > +++ b/drivers/mfd/Makefile
> > @@ -231,6 +231,7 @@ obj-$(CONFIG_MFD_PALMAS) += palmas.o
> > obj-$(CONFIG_MFD_VIPERBOARD) += viperboard.o
> > obj-$(CONFIG_MFD_NTXEC) += ntxec.o
> > obj-$(CONFIG_MFD_RC5T583) += rc5t583.o rc5t583-irq.o
> > +obj-$(CONFIG_MFD_ROCKCHIP_MFPWM) += rockchip-mfpwm.o
> > obj-$(CONFIG_MFD_RK8XX) += rk8xx-core.o
> > obj-$(CONFIG_MFD_RK8XX_I2C) += rk8xx-i2c.o
> > obj-$(CONFIG_MFD_RK8XX_SPI) += rk8xx-spi.o
> > diff --git a/drivers/mfd/rockchip-mfpwm.c b/drivers/mfd/rockchip-mfpwm.c
> > new file mode 100644
> > index 000000000000..08c2d8da41b7
> > --- /dev/null
> > +++ b/drivers/mfd/rockchip-mfpwm.c
> > @@ -0,0 +1,340 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * Copyright (c) 2025 Collabora Ltd.
> > + *
> > + * A driver to manage all the different functionalities exposed by Rockchip's
> > + * PWMv4 hardware.
> > + *
> > + * This driver is chiefly focused on guaranteeing non-concurrent operation
> > + * between the different device functions, as well as setting the clocks.
> > + * It registers the device function platform devices, e.g. PWM output or
> > + * PWM capture.
> > + *
> > + * Authors:
> > + * Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
> > + */
> > +
> > +#include <linux/array_size.h>
> > +#include <linux/clk.h>
> > +#include <linux/clk-provider.h>
> > +#include <linux/mfd/core.h>
> > +#include <linux/mfd/rockchip-mfpwm.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/overflow.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/spinlock.h>
> > +
> > +/**
> > + * struct rockchip_mfpwm - private mfpwm driver instance state struct
> > + * @pdev: pointer to this instance's &struct platform_device
> > + * @base: pointer to the memory mapped registers of this device
> > + * @pwm_clk: pointer to the PLL clock the PWM signal may be derived from
> > + * @osc_clk: pointer to the fixed crystal the PWM signal may be derived from
> > + * @rc_clk: pointer to the RC oscillator the PWM signal may be derived from
> > + * @chosen_clk: a clk-mux of pwm_clk, osc_clk and rc_clk
> > + * @pclk: pointer to the APB bus clock needed for mmio register access
> > + * @active_func: pointer to the currently active device function, or %NULL if no
> > + * device function is currently actively using any of the shared
> > + * resources. May only be checked/modified with @state_lock held.
> > + * @acquire_cnt: number of times @active_func has currently mfpwm_acquire()'d
> > + * it. Must only be checked or modified while holding @state_lock.
> > + * @state_lock: this lock is held while either the active device function, the
> > + * enable register, or the chosen clock is being changed.
> > + * @irq: the IRQ number of this device
> > + */
> > +struct rockchip_mfpwm {
> > + struct platform_device *pdev;
> > + void __iomem *base;
> > + struct clk *pwm_clk;
> > + struct clk *osc_clk;
> > + struct clk *rc_clk;
> > + struct clk *chosen_clk;
> > + struct clk *pclk;
> > + struct rockchip_mfpwm_func *active_func;
> > + unsigned int acquire_cnt;
> > + spinlock_t state_lock;
> > + int irq;
> > +};
> > +
> > +static atomic_t subdev_id = ATOMIC_INIT(0);
> > +
> > +static inline struct rockchip_mfpwm *to_rockchip_mfpwm(struct platform_device *pdev)
> > +{
> > + return platform_get_drvdata(pdev);
> > +}
> > +
> > +static int mfpwm_check_pwmf(const struct rockchip_mfpwm_func *pwmf,
> > + const char *fname)
> > +{
> > + struct device *dev = &pwmf->parent->pdev->dev;
> > +
> > + if (IS_ERR_OR_NULL(pwmf)) {
> > + dev_warn(dev, "called %s with an erroneous handle, no effect\n",
> > + fname);
> > + return -EINVAL;
> > + }
> > +
> > + if (IS_ERR_OR_NULL(pwmf->parent)) {
> > + dev_warn(dev, "called %s with an erroneous mfpwm_func parent, no effect\n",
> > + fname);
> > + return -EINVAL;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +__attribute__((nonnull))
> > +static int mfpwm_do_acquire(struct rockchip_mfpwm_func *pwmf)
> > +{
> > + struct rockchip_mfpwm *mfpwm = pwmf->parent;
> > + unsigned int cnt;
> > +
> > + if (mfpwm->active_func && pwmf->id != mfpwm->active_func->id)
> > + return -EBUSY;
> > +
> > + if (!mfpwm->active_func)
> > + mfpwm->active_func = pwmf;
> > +
> > + if (!check_add_overflow(mfpwm->acquire_cnt, 1, &cnt)) {
> > + mfpwm->acquire_cnt = cnt;
> > + } else {
> > + dev_warn(&mfpwm->pdev->dev, "prevented acquire counter overflow in %s\n",
> > + __func__);
> > + return -EOVERFLOW;
> > + }
> > +
> > + dev_dbg(&mfpwm->pdev->dev, "%d acquired mfpwm, acquires now at %u\n",
> > + pwmf->id, mfpwm->acquire_cnt);
> > +
> > + return clk_enable(mfpwm->pclk);
> > +}
> > +
> > +int mfpwm_acquire(struct rockchip_mfpwm_func *pwmf)
> > +{
> > + struct rockchip_mfpwm *mfpwm;
> > + unsigned long flags;
> > + int ret = 0;
> > +
> > + ret = mfpwm_check_pwmf(pwmf, "mfpwm_acquire");
> > + if (ret)
> > + return ret;
> > +
> > + mfpwm = pwmf->parent;
> > + dev_dbg(&mfpwm->pdev->dev, "%d is attempting to acquire\n", pwmf->id);
> > +
> > + if (!spin_trylock_irqsave(&mfpwm->state_lock, flags))
> > + return -EBUSY;
> > +
> > + ret = mfpwm_do_acquire(pwmf);
> > +
> > + spin_unlock_irqrestore(&mfpwm->state_lock, flags);
> > +
> > + return ret;
> > +}
> > +EXPORT_SYMBOL_NS_GPL(mfpwm_acquire, "ROCKCHIP_MFPWM");
> > +
> > +__attribute__((nonnull))
> > +static void mfpwm_do_release(const struct rockchip_mfpwm_func *pwmf)
> > +{
> > + struct rockchip_mfpwm *mfpwm = pwmf->parent;
> > +
> > + if (!mfpwm->active_func)
> > + return;
> > +
> > + if (mfpwm->active_func->id != pwmf->id)
> > + return;
> > +
> > + /*
> > + * No need to check_sub_overflow here, !mfpwm->active_func above catches
> > + * this type of problem already.
> > + */
> > + mfpwm->acquire_cnt--;
> > +
> > + if (!mfpwm->acquire_cnt)
> > + mfpwm->active_func = NULL;
> > +
> > + clk_disable(mfpwm->pclk);
> > +}
> > +
> > +void mfpwm_release(const struct rockchip_mfpwm_func *pwmf)
> > +{
> > + struct rockchip_mfpwm *mfpwm;
> > + unsigned long flags;
> > +
> > + if (mfpwm_check_pwmf(pwmf, "mfpwm_release"))
> > + return;
> > +
> > + mfpwm = pwmf->parent;
> > +
> > + spin_lock_irqsave(&mfpwm->state_lock, flags);
> > + mfpwm_do_release(pwmf);
> > + dev_dbg(&mfpwm->pdev->dev, "%d released mfpwm, acquires now at %u\n",
> > + pwmf->id, mfpwm->acquire_cnt);
> > + spin_unlock_irqrestore(&mfpwm->state_lock, flags);
> > +}
> > +EXPORT_SYMBOL_NS_GPL(mfpwm_release, "ROCKCHIP_MFPWM");
> > +
> > +/**
> > + * mfpwm_register_subdev - register a single mfpwm_func
> > + * @mfpwm: pointer to the parent &struct rockchip_mfpwm
> > + * @name: sub-device name string
> > + *
> > + * Allocate a single &struct mfpwm_func, fill its members with appropriate data,
> > + * and register a new mfd cell.
> > + *
> > + * Returns: 0 on success, negative errno on error
> > + */
> > +static int mfpwm_register_subdev(struct rockchip_mfpwm *mfpwm,
> > + const char *name)
> > +{
> > + struct rockchip_mfpwm_func *func;
> > + struct mfd_cell cell = {};
> > +
> > + func = devm_kzalloc(&mfpwm->pdev->dev, sizeof(*func), GFP_KERNEL);
> > + if (IS_ERR(func))
> > + return PTR_ERR(func);
> > + func->irq = mfpwm->irq;
> > + func->parent = mfpwm;
> > + func->id = atomic_inc_return(&subdev_id);
> > + func->base = mfpwm->base;
> > + func->core = mfpwm->chosen_clk;
> > + cell.name = name;
> > + cell.platform_data = func;
> > + cell.pdata_size = sizeof(*func);
> > + // cell.ignore_resource_conflicts = true;
> > + // cell.resources = mfpwm->pdev->resource;
> > + // cell.num_resources = mfpwm->pdev->num_resources;
> > +
> > + return devm_mfd_add_devices(&mfpwm->pdev->dev, func->id, &cell, 1, NULL,
> > + 0, NULL);
> > +}
> > +
> > +static int mfpwm_register_subdevs(struct rockchip_mfpwm *mfpwm)
> > +{
> > + int ret;
> > +
>
> > + ret = mfpwm_register_subdev(mfpwm, "pwm-rockchip-v4");
>
> Not sure who came up with this name?
> In case we need to filter wouldn't be easier to order it just like the bindings: manufacture '-' function

Please snip your replies in the future.

--
Lee Jones [李琼斯]