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From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Baruch Siach <baruch@tkos.co.il>
Cc: Thierry Reding <thierry.reding@gmail.com>,
	Lee Jones <lee.jones@linaro.org>, Andy Gross <agross@kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Balaji Prakash J <bjagadee@codeaurora.org>,
	Rob Herring <robh+dt@kernel.org>,
	Robert Marko <robert.marko@sartura.hr>,
	devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/3] pwm: driver for qualcomm ipq6018 pwm block
Date: Sat, 22 May 2021 23:35:24 +0200	[thread overview]
Message-ID: <20210522213524.lnb5bds5hvv2f2zi@pengutronix.de> (raw)
In-Reply-To: <70ced827689b7ab35d8f3b07db8d9ccd1489e3e2.1621410526.git.baruch@tkos.co.il>

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Hello Baruch,

On Wed, May 19, 2021 at 10:48:44AM +0300, Baruch Siach wrote:
> Driver for the PWM block in Qualcomm IPQ6018 line of SoCs. Based on
> driver from downstream Codeaurora kernel tree. Removed support for older
> (V1) variants because I have no access to that hardware.
> 
> Tested on IPQ6010 based hardware.
> 
> Signed-off-by: Baruch Siach <baruch@tkos.co.il>
> ---
>  drivers/pwm/Kconfig   |  12 ++
>  drivers/pwm/Makefile  |   1 +
>  drivers/pwm/pwm-ipq.c | 263 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 276 insertions(+)
>  create mode 100644 drivers/pwm/pwm-ipq.c
> 
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 9a4f66ae8070..54ef62a27bdc 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -260,6 +260,18 @@ config PWM_INTEL_LGM
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called pwm-intel-lgm.
>  
> +config PWM_IPQ
> +	tristate "IPQ PWM support"
> +	depends on ARCH_QCOM || COMPILE_TEST
> +	depends on HAVE_CLK && HAS_IOMEM
> +	help
> +	  Generic PWM framework driver for IPQ PWM block which supports
> +	  4 pwm channels. Each of the these channels can be configured
> +	  independent of each other.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called pwm-ipq.
> +
>  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 6374d3b1d6f3..73eb955dea1d 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -22,6 +22,7 @@ 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-$(CONFIG_PWM_IPQ)		+= pwm-ipq.o
>  obj-$(CONFIG_PWM_IQS620A)	+= pwm-iqs620a.o
>  obj-$(CONFIG_PWM_JZ4740)	+= pwm-jz4740.o
>  obj-$(CONFIG_PWM_KEEMBAY)	+= pwm-keembay.o
> diff --git a/drivers/pwm/pwm-ipq.c b/drivers/pwm/pwm-ipq.c
> new file mode 100644
> index 000000000000..885cf885fcf6
> --- /dev/null
> +++ b/drivers/pwm/pwm-ipq.c
> @@ -0,0 +1,263 @@
> +// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
> +/*
> + * Copyright (c) 2016-2017, 2020 The Linux Foundation. All rights reserved.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/clk.h>
> +#include <linux/io.h>
> +#include <asm/div64.h>
> +#include <linux/of_device.h>
> +
> +#define CLK_SRC_FREQ		(100*1000*1000)
> +#define MAX_PWM_DEVICES		4
> +
> +/* The default period and duty cycle values to be configured. */
> +#define DEFAULT_PERIOD_NS	10
> +#define DEFAULT_DUTY_CYCLE_NS	5

These define's names are too generic. Please prefix them with your
driver's name.

> +/*
> + * Enable bit is set to enable output toggling in pwm device.
> + * Update bit is set to reflect the changed divider and high duration
> + * values in register.
> + */
> +#define PWM_ENABLE		0x80000000
> +#define PWM_UPDATE		0x40000000
> +
> +/* The frequency range supported is 1Hz to 100MHz */
> +#define MIN_PERIOD_NS	10
> +#define MAX_PERIOD_NS	1000000000
> +
> +/*
> + * The max value specified for each field is based on the number of bits
> + * in the pwm control register for that field
> + */
> +#define MAX_PWM_CFG		0xFFFF
> +
> +#define PWM_CTRL_HI_SHIFT	16
> +
> +#define PWM_CFG_REG0 0 /*PWM_DIV PWM_HI*/
> +#define PWM_CFG_REG1 1 /*ENABLE UPDATE PWM_PRE_DIV*/
> +
> +struct ipq_pwm_chip {
> +	struct pwm_chip chip;
> +	struct clk *clk;
> +	void __iomem *mem;
> +};
> +
> +static struct ipq_pwm_chip *to_ipq_pwm_chip(struct pwm_chip *chip)
> +{
> +	return container_of(chip, struct ipq_pwm_chip, chip);
> +}
> +
> +static unsigned ipq_pwm_reg_offset(struct pwm_device *pwm, unsigned reg)
> +{
> +	return ((pwm->hwpwm * 2) + reg) * 4;
> +}
> +
> +static void config_div_and_duty(struct pwm_device *pwm, int pre_div,
> +			unsigned long long pwm_div, unsigned long period_ns,
> +			unsigned long long duty_ns)
> +{
> +	unsigned long hi_dur;
> +	unsigned long long quotient;
> +	unsigned long val = 0;
> +	struct ipq_pwm_chip *ipq_chip = to_ipq_pwm_chip(pwm->chip);
> +
> +	/*
> +	 * high duration = pwm duty * ( pwm div + 1)

s/( /(/

> +	 * pwm duty = duty_ns / period_ns
> +	 */
> +	quotient = (pwm_div + 1) * duty_ns;
> +	do_div(quotient, period_ns);
> +	hi_dur = quotient;
> +
> +	val |= ((hi_dur & MAX_PWM_CFG) << PWM_CTRL_HI_SHIFT);
> +	val |= (pwm_div & MAX_PWM_CFG);
> +	writel(val, ipq_chip->mem + ipq_pwm_reg_offset(pwm, PWM_CFG_REG0));
> +	val = pre_div & MAX_PWM_CFG;
> +	writel(val, ipq_chip->mem + ipq_pwm_reg_offset(pwm, PWM_CFG_REG1));
> +}
> +
> +static int ipq_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> +	struct ipq_pwm_chip *ipq_chip = to_ipq_pwm_chip(pwm->chip);
> +	unsigned offset = ipq_pwm_reg_offset(pwm, PWM_CFG_REG1);
> +	unsigned long val;
> +
> +	val = readl(ipq_chip->mem + offset);
> +	val |= (PWM_ENABLE | PWM_UPDATE);

The parenthesis are not needed here.

> +	writel(val, ipq_chip->mem + offset);
> +
> +	return 0;
> +}
> +
> +static void ipq_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> +	struct ipq_pwm_chip *ipq_chip = to_ipq_pwm_chip(pwm->chip);
> +	unsigned offset = ipq_pwm_reg_offset(pwm, PWM_CFG_REG1);
> +	unsigned long val;
> +
> +	val = readl(ipq_chip->mem + offset);
> +	val |= PWM_UPDATE;

What is the effect of this register bit?

Does the output become inactive or does it freeze at state that happens
to be emitted when the ENABLE bit is removed?

> +	val &= ~PWM_ENABLE;
> +	writel(val, ipq_chip->mem + offset);
> +}
> +
> +static int ipq_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> +						int duty_ns, int period_ns)
> +{
> +	struct ipq_pwm_chip *ipq_chip = to_ipq_pwm_chip(chip);
> +	unsigned long freq;
> +	int pre_div, close_pre_div, close_pwm_div;
> +	int pwm_div;
> +	long long diff;
> +	unsigned long rate = clk_get_rate(ipq_chip->clk);
> +	unsigned long min_diff = rate;
> +	uint64_t fin_ps;
> +
> +	if (period_ns > MAX_PERIOD_NS || period_ns < MIN_PERIOD_NS) {
> +		pr_err("PWM Frequency range supported is %dHz to %dHz\n"
> +			"Switching to default configuration values\n",
> +		       (int)NSEC_PER_SEC / MAX_PERIOD_NS,
> +		       (int)NSEC_PER_SEC / MIN_PERIOD_NS);
> +		period_ns = DEFAULT_PERIOD_NS;
> +		duty_ns = DEFAULT_DUTY_CYCLE_NS;
> +		pwm->state.period = period_ns;
> +		pwm->state.duty_cycle = duty_ns;
> +	}

Please implement the biggest period not bigger than the requested
period. That is do something like:

	if (period_ns < MIN_PERIOD_NS)
		return -ERANGE;

	if (period_ns > MAX_PERIOD_NS)
		period_ns = MAX_PERIOD_NS;

> +
> +	/* freq in Hz for period in nano second*/
> +	freq = NSEC_PER_SEC / period_ns;
> +	fin_ps = (uint64_t)NSEC_PER_SEC * 1000;
> +	do_div(fin_ps, rate);
> +	close_pre_div = MAX_PWM_CFG;
> +	close_pwm_div = MAX_PWM_CFG;
> +
> +	ipq_pwm_disable(chip, pwm);

This is necessary?

> +	for (pre_div = 0; pre_div <= MAX_PWM_CFG; pre_div++) {
> +		pwm_div = DIV_ROUND_CLOSEST_ULL((uint64_t)period_ns * 1000,
> +							fin_ps * (pre_div + 1));
> +		pwm_div--;

What if pwm_div was 0 before? (Didn't check if this can happen, maybe it
doesn't with period_ns >= MIN_PERIOD_NS?)

> +		if (pwm_div <= MAX_PWM_CFG) {
> +			diff = (uint64_t)rate - ((uint64_t)freq * (pre_div + 1) * (pwm_div + 1));
> +
> +			if (diff < 0)
> +				diff = -diff;
> +			if (!diff) {
> +				close_pre_div = pre_div;
> +				close_pwm_div = pwm_div;
> +				break;
> +			}
> +			if (diff < min_diff) {
> +				min_diff = diff;
> +				close_pre_div = pre_div;
> +				close_pwm_div = pwm_div;
> +			}

As written above: Never pick a period bigger than the requested period.

> +		}
> +	}
> +
> +	/* config divider values for the closest possible frequency */
> +	config_div_and_duty(pwm, close_pre_div, close_pwm_div,
> +					period_ns, duty_ns);

Please align follow up lines to the opening (.

> +	if (pwm->state.enabled)
> +		ipq_pwm_enable(chip, pwm);
> +
> +	return 0;
> +}
> +
> +static int ipq_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> +	pwm->state.period = DEFAULT_PERIOD_NS;
> +	pwm->state.duty_cycle = DEFAULT_DUTY_CYCLE_NS;
> +
> +	ipq_pwm_config(chip, pwm, pwm->state.duty_cycle, pwm->state.period);

.request is not supposed to modify the emitted wave form.

> +
> +	return 0;
> +}
> +
> +static void ipq_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> +	ipq_pwm_disable(chip, pwm);

neither is .free.

> +}
> +
> +static struct pwm_ops ipq_pwm_ops = {
> +	.request = ipq_pwm_request,
> +	.free = ipq_pwm_free,
> +	.config = ipq_pwm_config,
> +	.enable = ipq_pwm_enable,
> +	.disable = ipq_pwm_disable,

Please implement .apply instead of .config/.enable/.disable.

If you had enabled PWM_DEBUG during your tests you would have noticed
yourself ...

> +	.owner = THIS_MODULE,
> +};
> +
> +static int ipq_pwm_probe(struct platform_device *pdev)
> +{
> +	struct ipq_pwm_chip *pwm;
> +	struct device *dev;
> +	int ret;
> +
> +	dev = &pdev->dev;
> +	pwm = devm_kzalloc(dev, sizeof(*pwm), GFP_KERNEL);
> +	if (!pwm) {
> +		dev_err(dev, "failed to allocate memory\n");

You're not supposed to emit a message for -ENOMEM type errors. This is
already loud enough.

> +		return -ENOMEM;
> +	}
> +
> +	platform_set_drvdata(pdev, pwm);
> +
> +	pwm->mem = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(pwm->mem))
> +		return PTR_ERR(pwm->mem);
> +
> +	pwm->clk = devm_clk_get(dev, "core");
> +	if (!IS_ERR(pwm->clk)) {

If devm_clk_get() returns an error you should return an error, too.
You might want to use devm_clk_get_optional().

> +		ret = clk_set_rate(pwm->clk, CLK_SRC_FREQ);
> +		if (ret)
> +			return ret;
> +		ret = clk_prepare_enable(pwm->clk);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	pwm->chip.dev = dev;
> +	pwm->chip.ops = &ipq_pwm_ops;
> +	pwm->chip.npwm = MAX_PWM_DEVICES;
> +
> +	ret = pwmchip_add(&pwm->chip);
> +	if (ret < 0) {
> +		dev_err(dev, "pwmchip_add() failed: %d\n", ret);
> +		return ret;

	return dev_err_probe(dev, ret, "...")

please. And you have to disable the clock again.

> +	}
> +
> +	return 0;
> +}
> +
> +static int ipq_pwm_remove(struct platform_device *pdev)
> +{
> +	struct ipq_pwm_chip *pwm = platform_get_drvdata(pdev);
> +
> +	return pwmchip_remove(&pwm->chip);

Please ignore the return value of pwmchip_remove(). This is eventually
changed to return void.

> +}
> +
> +static const struct of_device_id pwm_ipq_dt_match[] = {
> +	{ .compatible = "qcom,pwm-ipq6018", },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, pwm_ipq_dt_match);
> +
> +static struct platform_driver ipq_pwm_driver = {
> +	.driver = {
> +		.name = "ipq-pwm",
> +		.owner = THIS_MODULE,
> +		.of_match_table = pwm_ipq_dt_match,
> +	},
> +	.probe = ipq_pwm_probe,
> +	.remove = ipq_pwm_remove,
> +};
> +
> +module_platform_driver(ipq_pwm_driver);
> +
> +MODULE_LICENSE("Dual BSD/GPL");

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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  parent reply	other threads:[~2021-05-22 21:35 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-19  7:48 Baruch Siach
2021-05-19  7:48 ` [PATCH 2/3] dt-bindings: pwm: add IPQ6018 binding Baruch Siach
2021-05-21  1:34   ` Rob Herring
2021-05-19  7:48 ` [PATCH 3/3] arm64: dts: ipq6018: add pwm node Baruch Siach
2021-05-22 21:35 ` Uwe Kleine-König [this message]
2021-05-23 15:54   ` [PATCH 1/3] pwm: driver for qualcomm ipq6018 pwm block Baruch Siach
2021-05-22 21:37 ` Uwe Kleine-König

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