Hello,
just a few minor things left to criticize, see below.
On Sun, Feb 20, 2022 at 04:50:30PM +0500, Nikita Travkin wrote:
> Some systems have clocks exposed to external devices. If the clock
> controller supports duty-cycle configuration, such clocks can be used as
> pwm outputs. In fact PWM and CLK subsystems are interfaced with in a
> similar way and an "opposite" driver already exists (clk-pwm). Add a
> driver that would enable pwm devices to be used via clk subsystem.
>
> Signed-off-by: Nikita Travkin <nikita@xxxxxxx>
> --
>
> Changes in v2:
> - Address Uwe's review comments:
> - Round set clk rate up
> - Add a description with limitations of the driver
> - Disable and unprepare clock before removing pwmchip
> Changes in v3:
> - Use 64bit version of div round up
> - Address Uwe's review comments:
> - Reword the limitations to avoid incorrect claims
> - Move the clk_enabled flag assignment
> - Drop unnecessary statements
> Changes in v5:
> - add missed returns
> Changes in v6:
> - Unprepare the clock on error
> - Drop redundant limitations points
> ---
> drivers/pwm/Kconfig | 10 +++
> drivers/pwm/Makefile | 1 +
> drivers/pwm/pwm-clk.c | 139 ++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 150 insertions(+)
> create mode 100644 drivers/pwm/pwm-clk.c
>
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 21e3b05a5153..daa2491a4054 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -140,6 +140,16 @@ config PWM_BRCMSTB
> To compile this driver as a module, choose M Here: the module
> will be called pwm-brcmstb.c.
>
> +config PWM_CLK
> + tristate "Clock based PWM support"
> + depends on HAVE_CLK || COMPILE_TEST
Can you really compile this driver if HAVE_CLK isn't available?
> + help
> + Generic PWM framework driver for outputs that can be
> + muxed to clocks.
> +
> + To compile this driver as a module, choose M here: the module
> + will be called pwm-clk.
> +
> config PWM_CLPS711X
> tristate "CLPS711X PWM support"
> depends on ARCH_CLPS711X || COMPILE_TEST
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index 708840b7fba8..4a860103c470 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -10,6 +10,7 @@ obj-$(CONFIG_PWM_BCM_KONA) += pwm-bcm-kona.o
> obj-$(CONFIG_PWM_BCM2835) += pwm-bcm2835.o
> obj-$(CONFIG_PWM_BERLIN) += pwm-berlin.o
> obj-$(CONFIG_PWM_BRCMSTB) += pwm-brcmstb.o
> +obj-$(CONFIG_PWM_CLK) += pwm-clk.o
> obj-$(CONFIG_PWM_CLPS711X) += pwm-clps711x.o
> obj-$(CONFIG_PWM_CRC) += pwm-crc.o
> obj-$(CONFIG_PWM_CROS_EC) += pwm-cros-ec.o
> diff --git a/drivers/pwm/pwm-clk.c b/drivers/pwm/pwm-clk.c
> new file mode 100644
> index 000000000000..52c9923368cb
> --- /dev/null
> +++ b/drivers/pwm/pwm-clk.c
> @@ -0,0 +1,139 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Clock based PWM controller
> + *
> + * Copyright (c) 2021 Nikita Travkin <nikita@xxxxxxx>
> + *
> + * This is an "adapter" driver that allows PWM consumers to use
> + * system clocks with duty cycle control as PWM outputs.
> + *
> + * Limitations:
> + * - Due to the fact that exact behavior depends on the underlying
> + * clock driver, various limitations are possible.
> + * - Underlying clock may not be able to give 0% or 100% duty cycle
> + * (constant off or on), exact behavior will depend on the clock.
> + * - When the PWM is disabled, the clock will be disabled as well,
> + * line state will depend on the clock.
- The clk API doesn't expose the necessary calls to implement
.get_state().
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/math64.h>
> +#include <linux/err.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/clk.h>
> +#include <linux/pwm.h>
> +
> +struct pwm_clk_chip {
> + struct pwm_chip chip;
> + struct clk *clk;
> + bool clk_enabled;
> +};
> +
> +#define to_pwm_clk_chip(_chip) container_of(_chip, struct pwm_clk_chip, chip)
> +
> +static int pwm_clk_apply(struct pwm_chip *pwm_chip, struct pwm_device *pwm,
> + const struct pwm_state *state)
> +{
> + struct pwm_clk_chip *chip = to_pwm_clk_chip(pwm_chip);
I'd prefer this was not called chip, as this is how struct pwm_chip
variables are called usually. My suggestion is:
chip -> pcchip
pwm_chip -> chip
Best regards
Uwe
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