Hi Rahul,

I just have some small nitpicks, see below:

On Wed, 2020-09-09 at 15:51 +0800, Rahul Tanwar wrote:
> Intel Lightning Mountain(LGM) SoC contains a PWM fan controller.
> This PWM controller does not have any other consumer, it is a
> dedicated PWM controller for fan attached to the system. Add
> driver for this PWM fan controller.
> 
> Signed-off-by: Rahul Tanwar <rahul.tan...@linux.intel.com>
> Reviewed-by: Andy Shevchenko <andriy.shevche...@intel.com>
> ---
>  drivers/pwm/Kconfig         |  11 ++
>  drivers/pwm/Makefile        |   1 +
>  drivers/pwm/pwm-intel-lgm.c | 253 
> ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 265 insertions(+)
>  create mode 100644 drivers/pwm/pwm-intel-lgm.c
> 
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 7dbcf6973d33..4949c51fe90b 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -232,6 +232,17 @@ config PWM_IMX_TPM
>         To compile this driver as a module, choose M here: the module
>         will be called pwm-imx-tpm.
>  
> +config PWM_INTEL_LGM
> +     tristate "Intel LGM PWM support"
> +     depends on HAS_IOMEM
> +     depends on (OF && X86) || COMPILE_TEST
> +     select REGMAP_MMIO
> +     help
> +       Generic PWM fan controller driver for LGM SoC.
> +
> +       To compile this driver as a module, choose M here: the module
> +       will be called pwm-intel-lgm.
> +
>  config PWM_IQS620A
>       tristate "Azoteq IQS620A PWM support"
>       depends on MFD_IQS62X || COMPILE_TEST
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index 2c2ba0a03557..e9431b151694 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -20,6 +20,7 @@ obj-$(CONFIG_PWM_IMG)               += pwm-img.o
>  obj-$(CONFIG_PWM_IMX1)               += pwm-imx1.o
>  obj-$(CONFIG_PWM_IMX27)              += pwm-imx27.o
>  obj-$(CONFIG_PWM_IMX_TPM)    += pwm-imx-tpm.o
> +obj-$(CONFIG_PWM_INTEL_LGM)  += pwm-intel-lgm.o
>  obj-$(CONFIG_PWM_IQS620A)    += pwm-iqs620a.o
>  obj-$(CONFIG_PWM_JZ4740)     += pwm-jz4740.o
>  obj-$(CONFIG_PWM_LP3943)     += pwm-lp3943.o
> diff --git a/drivers/pwm/pwm-intel-lgm.c b/drivers/pwm/pwm-intel-lgm.c
> new file mode 100644
> index 000000000000..8e9f8cd3b7fb
> --- /dev/null
> +++ b/drivers/pwm/pwm-intel-lgm.c
> @@ -0,0 +1,253 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2020 Intel Corporation.
> + *
> + * Limitations:
> + * - The hardware supports fixed period which is dependent on 2/3 or 4
> + *   wire fan mode.
> + * - Supports normal polarity. Does not support changing polarity.
> + * - When PWM is disabled, output of PWM will become 0(inactive). It doesn't
> + *   keep track of running period.
> + * - When duty cycle is changed, PWM output may be a mix of previous setting
> + *   and new setting for the first period. From second period, the output is
> + *   based on new setting.
> + * - It is a dedicated PWM fan controller. There are no other consumers for
> + *   this PWM controller.
> + */
> +#include <linux/bitfield.h>
> +#include <linux/clk.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/pwm.h>
> +#include <linux/regmap.h>
> +#include <linux/reset.h>
> +
> +#define LGM_PWM_FAN_CON0             0x0
> +#define LGM_PWM_FAN_EN_EN            BIT(0)
> +#define LGM_PWM_FAN_EN_DIS           0x0
> +#define LGM_PWM_FAN_EN_MSK           BIT(0)
> +#define LGM_PWM_FAN_MODE_2WIRE               0x0
> +#define LGM_PWM_FAN_MODE_MSK         BIT(1)
> +#define LGM_PWM_FAN_DC_MSK           GENMASK(23, 16)
> +
> +#define LGM_PWM_FAN_CON1             0x4
> +#define LGM_PWM_FAN_MAX_RPM_MSK              GENMASK(15, 0)
> +
> +#define LGM_PWM_MAX_RPM                      (BIT(16) - 1)
> +#define LGM_PWM_DEFAULT_RPM          4000
> +#define LGM_PWM_MAX_DUTY_CYCLE               (BIT(8) - 1)
> +
> +#define LGM_PWM_DC_BITS                      8
> +
> +#define LGM_PWM_PERIOD_2WIRE_NS              (40 * NSEC_PER_MSEC)
> +
> +struct lgm_pwm_chip {
> +     struct pwm_chip chip;
> +     struct regmap *regmap;
> +     struct clk *clk;
> +     struct reset_control *rst;
> +     u32 period;
> +};
> +
> +static inline struct lgm_pwm_chip *to_lgm_pwm_chip(struct pwm_chip *chip)
> +{
> +     return container_of(chip, struct lgm_pwm_chip, chip);
> +}
> +
> +static int lgm_pwm_enable(struct pwm_chip *chip, bool enable)
> +{
> +     struct lgm_pwm_chip *pc = to_lgm_pwm_chip(chip);
> +     struct regmap *regmap = pc->regmap;
> +
> +     return regmap_update_bits(regmap, LGM_PWM_FAN_CON0, LGM_PWM_FAN_EN_MSK,
> +                               enable ? LGM_PWM_FAN_EN_EN : 
> LGM_PWM_FAN_EN_DIS);
> +}
> +
> +static int lgm_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> +                      const struct pwm_state *state)
> +{
> +     struct lgm_pwm_chip *pc = to_lgm_pwm_chip(chip);
> +     u32 duty_cycle, val;
> +     int ret;
> +
> +     /*
> +      * The hardware only supports
> +      * normal polarity and fixed period.
> +      */

That comment could be put on a single line.

> +     if (state->polarity != PWM_POLARITY_NORMAL || state->period < 
> pc->period)
> +             return -EINVAL;
> +
> +     if (!state->enabled)
> +             return lgm_pwm_enable(chip, 0);
> +
> +     duty_cycle = min_t(u64, state->duty_cycle, pc->period);
> +     val = duty_cycle * LGM_PWM_MAX_DUTY_CYCLE / pc->period;
> +
> +     ret = regmap_update_bits(pc->regmap, LGM_PWM_FAN_CON0, 
> LGM_PWM_FAN_DC_MSK,
> +                              FIELD_PREP(LGM_PWM_FAN_DC_MSK, val));
> +     if (ret)
> +             return ret;
> +
> +     return lgm_pwm_enable(chip, 1);
> +}
> +
> +static void lgm_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> +                           struct pwm_state *state)
> +{
> +     struct lgm_pwm_chip *pc = to_lgm_pwm_chip(chip);
> +     u32 duty, val;
> +
> +     state->enabled = regmap_test_bits(pc->regmap, LGM_PWM_FAN_CON0,
> +                                       LGM_PWM_FAN_EN_EN);
> +     state->polarity = PWM_POLARITY_NORMAL;
> +     state->period = pc->period; /* fixed period */
> +
> +     regmap_read(pc->regmap, LGM_PWM_FAN_CON0, &val);
> +     duty = FIELD_GET(LGM_PWM_FAN_DC_MSK, val);
> +     state->duty_cycle = DIV_ROUND_UP(duty * pc->period, 
> LGM_PWM_MAX_DUTY_CYCLE);
> +}
> +
> +static const struct pwm_ops lgm_pwm_ops = {
> +     .get_state = lgm_pwm_get_state,
> +     .apply = lgm_pwm_apply,
> +     .owner = THIS_MODULE,
> +};
> +
> +static void lgm_pwm_init(struct lgm_pwm_chip *pc)
> +{
> +     struct regmap *regmap = pc->regmap;
> +     u32 con0_val;
> +
> +     con0_val = FIELD_PREP(LGM_PWM_FAN_MODE_MSK, LGM_PWM_FAN_MODE_2WIRE);
> +     pc->period = LGM_PWM_PERIOD_2WIRE_NS;
> +     regmap_update_bits(regmap, LGM_PWM_FAN_CON1, LGM_PWM_FAN_MAX_RPM_MSK,
> +                        LGM_PWM_DEFAULT_RPM);
> +     regmap_update_bits(regmap, LGM_PWM_FAN_CON0, LGM_PWM_FAN_MODE_MSK,
> +                        con0_val);
> +}
> +
> +static const struct regmap_config lgm_pwm_regmap_config = {
> +     .reg_bits = 32,
> +     .reg_stride = 4,
> +     .val_bits = 32,
> +};
> +
> +static void lgm_clk_disable(void *data)
> +{
> +     struct lgm_pwm_chip *pc = data;
> +
> +     clk_disable_unprepare(pc->clk);
> +}
> +
> +static int lgm_clk_enable(struct device *dev, struct lgm_pwm_chip *pc)
> +{
> +     int ret;
> +
> +     ret = clk_prepare_enable(pc->clk);
> +     if (ret)
> +             return ret;
> +
> +     return devm_add_action_or_reset(dev, lgm_clk_disable, pc);
> +}
> +
> +static void lgm_reset_control_assert(void *data)
> +{
> +     struct lgm_pwm_chip *pc = data;
> +
> +     reset_control_assert(pc->rst);
> +}
> +
> +static int lgm_reset_control_deassert(struct device *dev, struct 
> lgm_pwm_chip *pc)
> +{
> +     int ret;
> +
> +     ret = reset_control_deassert(pc->rst);
> +     if (ret)
> +             return ret;
> +
> +     return devm_add_action_or_reset(dev, lgm_reset_control_assert, pc);
> +}
> +
> +static int lgm_pwm_probe(struct platform_device *pdev)
> +{
> +     struct device *dev = &pdev->dev;
> +     struct lgm_pwm_chip *pc;
> +     void __iomem *io_base;
> +     int ret;
> +
> +     pc = devm_kzalloc(dev, sizeof(*pc), GFP_KERNEL);
> +     if (!pc)
> +             return -ENOMEM;
> +
> +     io_base = devm_platform_ioremap_resource(pdev, 0);
> +     if (IS_ERR(io_base))
> +             return PTR_ERR(io_base);
> +
> +     pc->regmap = devm_regmap_init_mmio(dev, io_base, 
> &lgm_pwm_regmap_config);
> +     if (IS_ERR(pc->regmap))
> +             return dev_err_probe(dev, PTR_ERR(pc->regmap),
> +                                  "failed to init register map\n");
> +
> +     pc->rst = devm_reset_control_get_exclusive(dev, NULL);
> +     if (IS_ERR(pc->rst))
> +             return dev_err_probe(dev, PTR_ERR(pc->rst),
> +                                  "failed to get reset control\n");
> +
> +     ret = lgm_reset_control_deassert(dev, pc);
> +     if (ret)
> +             return dev_err_probe(dev, ret, "cannot deassert reset 
> control\n");

I would request all resources before deasserting the reset, that way
-EPROBE_DEFER due to missing clocks would keep the controller in reset.

> +     pc->clk = devm_clk_get(dev, NULL);
> +     if (IS_ERR(pc->clk))
> +             return dev_err_probe(dev, PTR_ERR(pc->clk), "failed to get 
> clock\n");
> +
> +     ret = lgm_clk_enable(dev, pc);
> +     if (ret) {
> +             dev_err(dev, "failed to enable clock\n");
> +             return ret;
> +     }
> +
> +     pc->chip.dev = dev;
> +     pc->chip.ops = &lgm_pwm_ops;
> +     pc->chip.npwm = 1;
> +
> +     lgm_pwm_init(pc);
> +
> +     ret = pwmchip_add(&pc->chip);
> +     if (ret < 0) {
> +             dev_err(dev, "failed to add PWM chip: %pe\n", ERR_PTR(ret));
> +             return ret;
> +     }
> +
> +     platform_set_drvdata(pdev, pc);
> +     return 0;
> +}
> +
> +static int lgm_pwm_remove(struct platform_device *pdev)
> +{
> +     struct lgm_pwm_chip *pc = platform_get_drvdata(pdev);
> +     int ret;
> +
> +     ret = pwmchip_remove(&pc->chip);
> +     if (ret < 0)
> +             return ret;
> +
> +     return 0;

You could just

        return pwmchip_remove(&pc->chip);

here.

regards
Philipp

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