Hi Andy,
-----Original Message-----
From: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Sent: Thursday, 15 October, 2020 4:12 PM
To: Ayyathurai, Vijayakannan <vijayakannan.ayyathurai@xxxxxxxxx>
Cc: thierry.reding@xxxxxxxxx; u.kleine-koenig@xxxxxxxxxxxxxx; robh+dt@xxxxxxxxxx; linux-pwm@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; Wan Mohamad, Wan Ahmad Zainie <wan.ahmad.zainie.wan.mohamad@xxxxxxxxx>; mgross@xxxxxxxxxxxxxxx; Raja Subramanian, Lakshmi Bai <lakshmi.bai.raja.subramanian@xxxxxxxxx>
Subject: Re: [PATCH v12 1/2] pwm: Add PWM driver for Intel Keem Bay
On Thu, Oct 15, 2020 at 03:36:09AM +0800, vijayakannan.ayyathurai@xxxxxxxxx wrote:
> From: Vijayakannan Ayyathurai <vijayakannan.ayyathurai@xxxxxxxxx>
>
> The Intel Keem Bay SoC requires PWM support.
> Add the pwm-keembay driver to enable this.
>
> Signed-off-by: Lai, Poey Seng <poey.seng.lai@xxxxxxxxx>
Missed Co-developed-by?
Sure. I will add my Co-developed-by tag.
> Co-developed-by: Vineetha G. Jaya Kumaran
> <vineetha.g.jaya.kumaran@xxxxxxxxx>
> Signed-off-by: Vineetha G. Jaya Kumaran
> <vineetha.g.jaya.kumaran@xxxxxxxxx>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> Signed-off-by: Vijayakannan Ayyathurai
> <vijayakannan.ayyathurai@xxxxxxxxx>
> ---
> drivers/pwm/Kconfig | 9 ++
> drivers/pwm/Makefile | 1 +
> drivers/pwm/pwm-keembay.c | 233
> ++++++++++++++++++++++++++++++++++++++
> 3 files changed, 243 insertions(+)
> create mode 100644 drivers/pwm/pwm-keembay.c
>
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig index
> 7dbcf6973d33..6129a9dbbfa8 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -254,6 +254,15 @@ config PWM_JZ4740
> To compile this driver as a module, choose M here: the module
> will be called pwm-jz4740.
>
> +config PWM_KEEMBAY
> + tristate "Intel Keem Bay PWM driver"
> + depends on ARCH_KEEMBAY || COMPILE_TEST
> + help
> + The platform driver for Intel Keem Bay PWM controller.
> +
> + To compile this driver as a module, choose M here: the module
> + will be called pwm-keembay.
> +
> config PWM_LP3943
> tristate "TI/National Semiconductor LP3943 PWM support"
> depends on MFD_LP3943
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile index
> 2c2ba0a03557..a1051122eb07 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -22,6 +22,7 @@ obj-$(CONFIG_PWM_IMX27) += pwm-imx27.o
> obj-$(CONFIG_PWM_IMX_TPM) += pwm-imx-tpm.o
> obj-$(CONFIG_PWM_IQS620A) += pwm-iqs620a.o
> obj-$(CONFIG_PWM_JZ4740) += pwm-jz4740.o
> +obj-$(CONFIG_PWM_KEEMBAY) += pwm-keembay.o
> obj-$(CONFIG_PWM_LP3943) += pwm-lp3943.o
> obj-$(CONFIG_PWM_LPC18XX_SCT) += pwm-lpc18xx-sct.o
> obj-$(CONFIG_PWM_LPC32XX) += pwm-lpc32xx.o
> diff --git a/drivers/pwm/pwm-keembay.c b/drivers/pwm/pwm-keembay.c new
> file mode 100644 index 000000000000..ced6d4010add
> --- /dev/null
> +++ b/drivers/pwm/pwm-keembay.c
> @@ -0,0 +1,233 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Intel Keem Bay PWM driver
> + *
> + * Copyright (C) 2020 Intel Corporation
> + * Authors: Lai Poey Seng <poey.seng.lai@xxxxxxxxx>
> + * Vineetha G. Jaya Kumaran <vineetha.g.jaya.kumaran@xxxxxxxxx>
> + *
> + * Limitations:
> + * - Upon disabling a channel, the currently running
> + * period will not be completed. However, upon
> + * reconfiguration of the duty cycle/period, the
> + * currently running period will be completed first.
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/clk.h>
> +#include <linux/io.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/regmap.h>
> +
> +#define KMB_TOTAL_PWM_CHANNELS 6
> +#define KMB_PWM_COUNT_MAX U16_MAX
> +#define KMB_PWM_EN_BIT BIT(31)
> +
> +/* Mask */
> +#define KMB_PWM_HIGH_MASK GENMASK(31, 16)
> +#define KMB_PWM_LOW_MASK GENMASK(15, 0)
> +#define KMB_PWM_LEADIN_MASK GENMASK(30, 0)
> +
> +/* PWM Register offset */
> +#define KMB_PWM_LEADIN_OFFSET(ch) (0x00 + 4 * (ch))
> +#define KMB_PWM_HIGHLOW_OFFSET(ch) (0x20 + 4 * (ch))
> +
> +struct keembay_pwm {
> + struct pwm_chip chip;
> + struct device *dev;
> + struct clk *clk;
> + void __iomem *base;
> +};
> +
> +static inline struct keembay_pwm *to_keembay_pwm_dev(struct pwm_chip
> +*chip) {
> + return container_of(chip, struct keembay_pwm, chip); }
> +
> +static inline void keembay_pwm_update_bits(struct keembay_pwm *priv, u32 mask,
> + u32 val, u32 offset)
> +{
> + u32 buff = readl(priv->base + offset);
> +
> + buff = u32_replace_bits(buff, val, mask);
> + writel(buff, priv->base + offset);
> +}
> +
> +static void keembay_pwm_enable(struct keembay_pwm *priv, int ch) {
> + keembay_pwm_update_bits(priv, KMB_PWM_EN_BIT, 1,
> + KMB_PWM_LEADIN_OFFSET(ch));
> +}
> +
> +static void keembay_pwm_disable(struct keembay_pwm *priv, int ch) {
> + keembay_pwm_update_bits(priv, KMB_PWM_EN_BIT, 0,
> + KMB_PWM_LEADIN_OFFSET(ch));
> +}
> +
> +static void keembay_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> + struct pwm_state *state)
> +{
> + struct keembay_pwm *priv = to_keembay_pwm_dev(chip);
> + unsigned long long high, low;
> + unsigned long clk_rate;
> + u32 highlow;
> +
> + clk_rate = clk_get_rate(priv->clk);
> +
> + /* Read channel enabled status */
> + highlow = readl(priv->base + KMB_PWM_LEADIN_OFFSET(pwm->hwpwm));
> + if (highlow & KMB_PWM_EN_BIT)
> + state->enabled = true;
> + else
> + state->enabled = false;
> +
> + /* Read period and duty cycle */
> + highlow = readl(priv->base + KMB_PWM_HIGHLOW_OFFSET(pwm->hwpwm));
> + low = FIELD_GET(KMB_PWM_LOW_MASK, highlow) * NSEC_PER_SEC;
> + high = FIELD_GET(KMB_PWM_HIGH_MASK, highlow) * NSEC_PER_SEC;
> + state->duty_cycle = DIV_ROUND_UP_ULL(high, clk_rate);
> + state->period = DIV_ROUND_UP_ULL(high + low, clk_rate);
> + state->polarity = PWM_POLARITY_NORMAL; }
> +
> +static int keembay_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> + const struct pwm_state *state) {
> + struct keembay_pwm *priv = to_keembay_pwm_dev(chip);
> + struct pwm_state current_state;
> + unsigned long long div;
> + unsigned long clk_rate;
> + u32 pwm_count = 0;
> + u16 high, low;
> +
> + if (state->polarity != PWM_POLARITY_NORMAL)
> + return -ENOSYS;
> +
> + /*
> + * Configure the pwm repeat count as infinite at (15:0) and leadin
> + * low time as 0 at (30:16), which is in terms of clock cycles.
> + */
> + keembay_pwm_update_bits(priv, KMB_PWM_LEADIN_MASK, 0,
> + KMB_PWM_LEADIN_OFFSET(pwm->hwpwm));
> +
> + keembay_pwm_get_state(chip, pwm, ¤t_state);
> +
> + if (!state->enabled) {
> + if (current_state.enabled)
> + keembay_pwm_disable(priv, pwm->hwpwm);
> + return 0;
> + }
> +
> + /*
> + * The upper 16 bits and lower 16 bits of the KMB_PWM_HIGHLOW_OFFSET
> + * register contain the high time and low time of waveform accordingly.
> + * All the values are in terms of clock cycles.
> + */
> +
> + clk_rate = clk_get_rate(priv->clk);
> + div = clk_rate * state->duty_cycle;
> + div = DIV_ROUND_DOWN_ULL(div, NSEC_PER_SEC);
> + if (div > KMB_PWM_COUNT_MAX)
> + return -ERANGE;
> +
> + high = div;
> + div = clk_rate * state->period;
> + div = DIV_ROUND_DOWN_ULL(div, NSEC_PER_SEC);
> + div = div - high;
> + if (div > KMB_PWM_COUNT_MAX)
> + return -ERANGE;
> +
> + low = div;
> +
> + pwm_count = FIELD_PREP(KMB_PWM_HIGH_MASK, high) |
> + FIELD_PREP(KMB_PWM_LOW_MASK, low);
> +
> + writel(pwm_count, priv->base + KMB_PWM_HIGHLOW_OFFSET(pwm->hwpwm));
> +
> + if (state->enabled && !current_state.enabled)
> + keembay_pwm_enable(priv, pwm->hwpwm);
> +
> + return 0;
> +}
> +
> +static const struct pwm_ops keembay_pwm_ops = {
> + .owner = THIS_MODULE,
> + .apply = keembay_pwm_apply,
> + .get_state = keembay_pwm_get_state,
> +};
> +
> +static int keembay_pwm_probe(struct platform_device *pdev) {
> + struct device *dev = &pdev->dev;
> + struct keembay_pwm *priv;
> + int ret;
> +
> + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + priv->clk = devm_clk_get(dev, NULL);
> + if (IS_ERR(priv->clk))
> + return dev_err_probe(dev, PTR_ERR(priv->clk), "Failed to get
> +clock\n");
> +
> + ret = clk_prepare_enable(priv->clk);
> + if (ret)
> + return ret;
> +
> + priv->base = devm_platform_ioremap_resource(pdev, 0);
> + if (IS_ERR(priv->base)) {
> + clk_disable_unprepare(priv->clk);
See below.
> + return PTR_ERR(priv->base);
> + }
> +
> + priv->chip.base = -1;
> + priv->chip.dev = dev;
> + priv->chip.ops = &keembay_pwm_ops;
> + priv->chip.npwm = KMB_TOTAL_PWM_CHANNELS;
> +
> + ret = pwmchip_add(&priv->chip);
> + if (ret) {
> + dev_err(dev, "Failed to add PWM chip: %pe\n", ERR_PTR(ret));
> + clk_disable_unprepare(priv->clk);
This messes up with ordering of things.
That's why devm golden rule is either all or none. You may fix this by switching to devm_add_action_or_reset().
One of possible way is like in below drivers:
% git grep -n devm_add_action_or_reset.*disable_unprepare -- drivers/
But it may be fixed in follow up change. Depends on maintainers' wishes.
Sure. I shall incorporate and check based on maintainers wish in the next version.
> + return ret;
> + }
> +
> + platform_set_drvdata(pdev, priv);
> +
> + return 0;
> +}
> +
> +static int keembay_pwm_remove(struct platform_device *pdev) {
> + struct keembay_pwm *priv = platform_get_drvdata(pdev);
> + int ret;
> +
> + ret = pwmchip_remove(&priv->chip);
> + clk_disable_unprepare(priv->clk);
> +
> + return ret;
...and this will be simplified to
return pwmchip_remove(&priv->chip);
Until v10, It is as per your suggestion. But I have changed it in v11 to overcome the issue mentioned by Uwe. I have kept the snip of v10 FYR below.
//Start snip from v10 review mailing list
//> +static int keembay_pwm_remove(struct platform_device *pdev) {
//> + struct keembay_pwm *priv = platform_get_drvdata(pdev);
//> +
//> + clk_disable_unprepare(priv->clk);
//> +
//> + return pwmchip_remove(&priv->chip);
//
//You have to call pwmchip_remove first. Otherwise you're stopping the PWM while the framework still believes everything to be fine.
//
//> +}
//End snip from v10 review mailing review
> +}
> +
> +static const struct of_device_id keembay_pwm_of_match[] = {
> + { .compatible = "intel,keembay-pwm" },
> + { }
> +};
> +MODULE_DEVICE_TABLE(of, keembay_pwm_of_match);
> +
> +static struct platform_driver keembay_pwm_driver = {
> + .probe = keembay_pwm_probe,
> + .remove = keembay_pwm_remove,
> + .driver = {
> + .name = "pwm-keembay",
> + .of_match_table = keembay_pwm_of_match,
> + },
> +};
> +module_platform_driver(keembay_pwm_driver);
> +
> +MODULE_ALIAS("platform:pwm-keembay");
> +MODULE_DESCRIPTION("Intel Keem Bay PWM driver"); MODULE_LICENSE("GPL
> +v2");
> --
> 2.17.1
>
--
With Best Regards,
Andy Shevchenko
Thanks,
Vijay
