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Date: Tue, 14 Feb 2017 15:54:44 +0100
From: Marcin Nowakowski <marcin.nowakowski@...tec.com>
To: Yang Ling <gnaygnil@...il.com>, <thierry.reding@...il.com>,
<keguang.zhang@...il.com>
CC: <linux-kernel@...r.kernel.org>, <linux-pwm@...r.kernel.org>,
<linux-mips@...ux-mips.org>
Subject: Re: [PATCH 1/2] pwm: loongson1: Add PWM driver for Loongson1 SoC
Hi Yang,
On 13.02.2017 16:28, Yang Ling wrote:
> Add support for the PWM controller present in Loongson1 family of SoCs.
>
> Signed-off-by: Yang Ling <gnaygnil@...il.com>
> ---
> drivers/pwm/Kconfig | 9 +++
> drivers/pwm/Makefile | 1 +
> drivers/pwm/pwm-loongson1.c | 169 ++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 179 insertions(+)
> create mode 100644 drivers/pwm/pwm-loongson1.c
>
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index f92dd41..985f2fe 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -216,6 +216,15 @@ config PWM_JZ4740
> To compile this driver as a module, choose M here: the module
> will be called pwm-jz4740.
>
> +config PWM_LOONGSON1
> + tristate "Loongson1 PWM support"
> + depends on MACH_LOONGSON32
> + help
> + Generic PWM framework driver for Loongson1 based machines.
> +
> + To compile this driver as a module, choose M here: the module
> + will be called pwm-loongson1.
> +
> 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 a48bdb5..1979453 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -19,6 +19,7 @@ obj-$(CONFIG_PWM_HIBVT) += pwm-hibvt.o
> obj-$(CONFIG_PWM_IMG) += pwm-img.o
> obj-$(CONFIG_PWM_IMX) += pwm-imx.o
> obj-$(CONFIG_PWM_JZ4740) += pwm-jz4740.o
> +obj-$(CONFIG_PWM_LOONGSON1) += pwm-loongson1.o
> obj-$(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-loongson1.c b/drivers/pwm/pwm-loongson1.c
> new file mode 100644
> index 0000000..72e3fe3
> --- /dev/null
> +++ b/drivers/pwm/pwm-loongson1.c
> @@ -0,0 +1,169 @@
> +/*
> + * Copyright (c) 2017 Yang Ling <gnaygnil@...il.com>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License as published by the
> + * Free Software Foundation; either version 2 of the License, or (at your
> + * option) any later version.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <loongson1.h>
> +
> +struct ls1x_pwm_chip {
> + struct clk *clk;
> + void __iomem *base;
> + struct pwm_chip chip;
> +};
> +
> +struct ls1x_pwm_channel {
> + u32 period_ns;
> + u32 duty_ns;
> +};
> +static inline struct ls1x_pwm_chip *to_ls1x_pwm_chip(struct pwm_chip *chip)
> +{
> + return container_of(chip, struct ls1x_pwm_chip, chip);
> +}
> +
> +static int ls1x_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> + struct ls1x_pwm_channel *chan = NULL;
> +
> + chan = devm_kzalloc(chip->dev, sizeof(*chan), GFP_KERNEL);
> + if (!chan)
> + return -ENOMEM;
> +
> + pwm_set_chip_data(pwm, chan);
> +
> + return 0;
> +}
> +
> +static void ls1x_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> + devm_kfree(chip->dev, pwm_get_chip_data(pwm));
> + pwm_set_chip_data(pwm, NULL);
> +}
> +
Period and duty are stored in the pwm_device already, so you're just
duplicating the same data here. If you remove ls1x_pwm_channel then all
of the code above becomes unnecessary ...
> +static int ls1x_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> + int duty_ns, int period_ns)
> +{
> + struct ls1x_pwm_chip *pc = to_ls1x_pwm_chip(chip);
> + struct ls1x_pwm_channel *chan = pwm_get_chip_data(pwm);
> + unsigned long long tmp;
> + unsigned long period, duty;
> +
> + if (period_ns == chan->period_ns && duty_ns == chan->duty_ns)
> + return 0;
> +
above check is already handled in pwm core
> + tmp = (unsigned long long)clk_get_rate(pc->clk) * period_ns;
> + do_div(tmp, 1000000000);
> + period = tmp;
> +
> + tmp = (unsigned long long)period * duty_ns;
> + do_div(tmp, period_ns);
> + duty = period - tmp;
> +
> + if (duty >= period)
> + duty = period - 1;
> +
> + if (duty >> 24 || period >> 24)
> + return -EINVAL;
> +
> + chan->period_ns = period_ns;
> + chan->duty_ns = duty_ns;
> +
> + writel(duty, pc->base + PWM_HRC(pwm->hwpwm));
> + writel(period, pc->base + PWM_LRC(pwm->hwpwm));
> + writel(0x00, pc->base + PWM_CNT(pwm->hwpwm));
> +
PWM_HRC and PWM_LRC names suggest that you're using high/low state
counters here rather than duty/period - but with no documentation I'm
just guessing here.
> + return 0;
> +}
> +
> +static int ls1x_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> + struct ls1x_pwm_chip *pc = to_ls1x_pwm_chip(chip);
> +
> + writel(CNT_RST, pc->base + PWM_CTRL(pwm->hwpwm));
> + writel(CNT_EN, pc->base + PWM_CTRL(pwm->hwpwm));
> +
> + return 0;
> +}
> +
> +static void ls1x_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> + struct ls1x_pwm_chip *pc = to_ls1x_pwm_chip(chip);
> +
> + writel(PWM_OE, pc->base + PWM_CTRL(pwm->hwpwm));
> +}
> +
> +static const struct pwm_ops ls1x_pwm_ops = {
> + .request = ls1x_pwm_request,
> + .free = ls1x_pwm_free,
> + .config = ls1x_pwm_config,
> + .enable = ls1x_pwm_enable,
> + .disable = ls1x_pwm_disable,
> + .owner = THIS_MODULE,
> +};
> +
> +static int ls1x_pwm_probe(struct platform_device *pdev)
> +{
> + struct ls1x_pwm_chip *pc = NULL;
> + struct resource *res = NULL;
> +
> + pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
> + if (!pc)
> + return -ENOMEM;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + pc->base = devm_ioremap_resource(&pdev->dev, res);
> + if (IS_ERR(pc->base))
> + return PTR_ERR(pc->base);
> +
> + pc->clk = devm_clk_get(&pdev->dev, "ls1x-pwmtimer");
> + if (IS_ERR(pc->clk)) {
> + dev_err(&pdev->dev, "failed to get %s clock\n", pdev->name);
> + return PTR_ERR(pc->clk);
> + }
> + clk_prepare_enable(pc->clk);
Should check for errors here
> + pc->chip.ops = &ls1x_pwm_ops;
> + pc->chip.dev = &pdev->dev;
> + pc->chip.base = -1;
> + pc->chip.npwm = 4;
> +
> + platform_set_drvdata(pdev, pc);
> +
> + return pwmchip_add(&pc->chip);
Should check for errors (and disable clk appropriately)
> +}
> +
> +static int ls1x_pwm_remove(struct platform_device *pdev)
> +{
> + struct ls1x_pwm_chip *pc = platform_get_drvdata(pdev);
> + int ret;
> +
> + ret = pwmchip_remove(&pc->chip);
> + if (ret < 0)
> + return ret;
> +
> + clk_disable_unprepare(pc->clk);
> +
> + return 0;
> +}
> +
> +static struct platform_driver ls1x_pwm_driver = {
> + .driver = {
> + .name = "ls1x-pwm",
> + },
> + .probe = ls1x_pwm_probe,
> + .remove = ls1x_pwm_remove,
> +};
> +module_platform_driver(ls1x_pwm_driver);
> +
> +MODULE_AUTHOR("Yang Ling <gnaygnil@...il.com>");
> +MODULE_DESCRIPTION("Loongson1 PWM driver");
> +MODULE_ALIAS("platform:loongson1-pwm");
> +MODULE_LICENSE("GPL");
>
Best regards,
Marcin
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