Re: [PATCH 1/3] pwm: driver for qualcomm ipq6018 pwm block

[Baruch Siach <baruch@tkos.co.il>]

Hi Devi,

On Fri, Sep 22 2023, Devi Priya wrote:
> On 9/15/2023 12:06 PM, Baruch Siach wrote:
>> Hi Devi,
>> [ Dropped/updated codeaurora.org addresses ]
>> On Fri, Sep 15 2023, Devi Priya wrote:
>>> On 2/7/2022 3:00 PM, Baruch Siach wrote:
>>>> From: Baruch Siach <baruch.siach@siklu.com>
>>>> 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.siach@siklu.com>
>>>> ---
>>>> v11:
>>>
>>> Just curious to know if you have plans to post the next revision!
>> I have been waiting for comments from pwm maintainers before sending the
>> next revision.
>> Unfortunately since then I lost access to the hardware, so I can't test
>> suggested implementation changes.  The only pending issue in v11 is the
>> trivial change that Nathan Chancellor suggested, which should be safe.
>> If you like to take it from here you are welcome.
>
> Could you pls point me to the pending comment that has to be addressed.
> Was not able to find any open comments in the latest series.
> https://lore.kernel.org/linux-arm-msm/8a331c88-c7d4-3a14-0ec3-fd616ea24a99@quicinc.com/

See here:

  https://lore.kernel.org/all/YgK63cI177ZeF5v1@dev-arch.archlinux-ax161/

baruch

>>>> Address comment from Uwe Kleine-König:
>>>>     Drop redundant registers field comments
>>>>     Fix period limit check in .apply
>>>>     Clarify the comment explaining skip of pre_div > pwm_div values
>>>>     Add explicit check for clock rate within limit
>>>>     Add comment explaining the selection of initial pre_div
>>>>     Use pwm_div division with remainder instead of separate diff calculation
>>>>     Round up duty_cycle calculation in .get_state
>>>> v10:
>>>>     Restore round up in pwm_div calculation; otherwise diff is always <=
>>>>     0, so only bingo match works
>>>>     Don't overwrite min_diff on every loop iteration
>>>> v9:
>>>> Address comment from Uwe Kleine-König:
>>>>     Use period_ns*rate in dividers calculation for better accuracy
>>>>     Round down pre_div and pwm_div
>>>>     Add a comment explaining why pwm_div can't underflow
>>>>     Add a comment explaining why pre_div > pwm_div end the search loop
>>>>     Drop 'CFG_' from register macros
>>>>     Rename to_ipq_pwm_chip() to ipq_pwm_from_chip()
>>>>     Change bare 'unsigned' to 'unsigned int'
>>>>     Clarify the comment on separate REG1 write for enable/disable
>>>>     Round up the period value in .get_state
>>>>     Use direct readl/writel so no need to check for regmap errors
>>>> v7:
>>>>     Change 'offset' to 'reg' for the tcsr offset (Rob)
>>>>     Drop clock name; there is only one clock (Bjorn)
>>>>     Simplify probe failure code path (Bjorn)
>>>> v6:
>>>> Address Uwe Kleine-König review comments:
>>>>     Drop IPQ_PWM_MAX_DEVICES
>>>>     Rely on assigned-clock-rates; drop IPQ_PWM_CLK_SRC_FREQ
>>>>     Simplify register offset calculation
>>>>     Calculate duty cycle more precisely
>>>>     Refuse to set inverted polarity
>>>>     Drop redundant IPQ_PWM_REG1_ENABLE bit clear
>>>>     Remove x1000 factor in pwm_div calculation, use rate directly, and round
>>>> up
>>>>     Choose initial pre_div such that pwm_div < IPQ_PWM_MAX_DIV
>>>>     Ensure pre_div <= pwm_div
>>>>     Rename close_ to best_
>>>>     Explain in comment why effective_div doesn't overflow
>>>>     Limit pwm_div to IPQ_PWM_MAX_DIV - 1 to allow 100% duty cycle
>>>>     Disable clock only after pwmchip_remove()
>>>>     const pwm_ops
>>>> Other changes:
>>>>     Add missing linux/bitfield.h header include (kernel test robot)
>>>>     Adjust code for PWM device node under TCSR (Rob Herring)
>>>> v5:
>>>> Use &tcsr_q6 syscon to access registers (Bjorn Andersson)
>>>> Address Uwe Kleine-König review comments:
>>>>     Implement .get_state()
>>>>     Add IPQ_PWM_ prefix to local macros
>>>>     Use GENMASK/BIT/FIELD_PREP for register fields access
>>>>     Make type of config_div_and_duty() parameters consistent
>>>>     Derive IPQ_PWM_MIN_PERIOD_NS from IPQ_PWM_CLK_SRC_FREQ
>>>>     Integrate enable/disable into config_div_and_duty() to save register
>>>> read,
>>>>     and reduce frequency glitch on update
>>>>     Use min() instead of min_t()
>>>>     Fix comment format
>>>>     Use dev_err_probe() to indicate probe step failure
>>>>     Add missing clk_disable_unprepare() in .remove
>>>>     Don't set .owner
>>>> v4:
>>>>     Use div64_u64() to fix link for 32-bit targets ((kernel test robot
>>>>     <lkp@intel.com>, Uwe Kleine-König)
>>>> v3:
>>>>     s/qcom,pwm-ipq6018/qcom,ipq6018-pwm/ (Rob Herring)
>>>>     Fix integer overflow on 32-bit targets (kernel test robot
>>>> <lkp@intel.com>)
>>>> v2:
>>>> Address Uwe Kleine-König review comments:
>>>>     Fix period calculation when out of range
>>>>     Don't set period larger than requested
>>>>     Remove PWM disable on configuration change
>>>>     Implement .apply instead of non-atomic .config/.enable/.disable
>>>>     Don't modify PWM on .request/.free
>>>>     Check pwm_div underflow
>>>>     Fix various code and comment formatting issues
>>>> Other changes:
>>>>     Use u64 divisor safe division
>>>>     Remove now empty .request/.free
>>>> ---
>>>>    drivers/pwm/Kconfig   |  12 ++
>>>>    drivers/pwm/Makefile  |   1 +
>>>>    drivers/pwm/pwm-ipq.c | 281 ++++++++++++++++++++++++++++++++++++++++++
>>>>    3 files changed, 294 insertions(+)
>>>>    create mode 100644 drivers/pwm/pwm-ipq.c
>>>> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
>>>> index 21e3b05a5153..e39718137ecd 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 708840b7fba8..7402feae4b36 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..994027290bcb
>>>> --- /dev/null
>>>> +++ b/drivers/pwm/pwm-ipq.c
>>>> @@ -0,0 +1,281 @@
>>>> +// 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 <linux/of.h>
>>>> +#include <linux/math64.h>
>>>> +#include <linux/of_device.h>
>>>> +#include <linux/bitfield.h>
>>>> +#include <linux/units.h>
>>>> +
>>>> +/* The frequency range supported is 1 Hz to clock rate */
>>>> +#define IPQ_PWM_MAX_PERIOD_NS	((u64)NSEC_PER_SEC)
>>>> +
>>>> +/*
>>>> + * The max value specified for each field is based on the number of bits
>>>> + * in the pwm control register for that field
>>>> + */
>>>> +#define IPQ_PWM_MAX_DIV		0xFFFF
>>>> +
>>>> +/*
>>>> + * Two 32-bit registers for each PWM: REG0, and REG1.
>>>> + * Base offset for PWM #i is at 8 * #i.
>>>> + */
>>>> +#define IPQ_PWM_REG0			0
>>>> +#define IPQ_PWM_REG0_PWM_DIV		GENMASK(15, 0)
>>>> +#define IPQ_PWM_REG0_HI_DURATION	GENMASK(31, 16)
>>>> +
>>>> +#define IPQ_PWM_REG1			4
>>>> +#define IPQ_PWM_REG1_PRE_DIV		GENMASK(15, 0)
>>>> +/*
>>>> + * 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 IPQ_PWM_REG1_UPDATE		BIT(30)
>>>> +#define IPQ_PWM_REG1_ENABLE		BIT(31)
>>>> +
>>>> +
>>>> +struct ipq_pwm_chip {
>>>> +	struct pwm_chip chip;
>>>> +	struct clk *clk;
>>>> +	void __iomem *mem;
>>>> +};
>>>> +
>>>> +static struct ipq_pwm_chip *ipq_pwm_from_chip(struct pwm_chip *chip)
>>>> +{
>>>> +	return container_of(chip, struct ipq_pwm_chip, chip);
>>>> +}
>>>> +
>>>> +static unsigned int ipq_pwm_reg_read(struct pwm_device *pwm, unsigned int reg)
>>>> +{
>>>> +	struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(pwm->chip);
>>>> +	unsigned int off = 8 * pwm->hwpwm + reg;
>>>> +
>>>> +	return readl(ipq_chip->mem + off);
>>>> +}
>>>> +
>>>> +static void ipq_pwm_reg_write(struct pwm_device *pwm, unsigned int reg,
>>>> +			      unsigned int val)
>>>> +{
>>>> +	struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(pwm->chip);
>>>> +	unsigned int off = 8 * pwm->hwpwm + reg;
>>>> +
>>>> +	writel(val, ipq_chip->mem + off);
>>>> +}
>>>> +
>>>> +static void config_div_and_duty(struct pwm_device *pwm, unsigned int pre_div,
>>>> +			unsigned int pwm_div, unsigned long rate, u64 duty_ns,
>>>> +			bool enable)
>>>> +{
>>>> +	unsigned long hi_dur;
>>>> +	unsigned long val = 0;
>>>> +
>>>> +	/*
>>>> +	 * high duration = pwm duty * (pwm div + 1)
>>>> +	 * pwm duty = duty_ns / period_ns
>>>> +	 */
>>>> +	hi_dur = div64_u64(duty_ns * rate, (pre_div + 1) * NSEC_PER_SEC);
>>>> +
>>>> +	val = FIELD_PREP(IPQ_PWM_REG0_HI_DURATION, hi_dur) |
>>>> +		FIELD_PREP(IPQ_PWM_REG0_PWM_DIV, pwm_div);
>>>> +	ipq_pwm_reg_write(pwm, IPQ_PWM_REG0, val);
>>>> +
>>>> +	val = FIELD_PREP(IPQ_PWM_REG1_PRE_DIV, pre_div);
>>>> +	ipq_pwm_reg_write(pwm, IPQ_PWM_REG1, val);
>>>> +
>>>> +	/* PWM enable toggle needs a separate write to REG1 */
>>>> +	val |= IPQ_PWM_REG1_UPDATE;
>>>> +	if (enable)
>>>> +		val |= IPQ_PWM_REG1_ENABLE;
>>>> +	ipq_pwm_reg_write(pwm, IPQ_PWM_REG1, val);
>>>> +}
>>>> +
>>>> +static int ipq_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>>>> +			 const struct pwm_state *state)
>>>> +{
>>>> +	struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(chip);
>>>> +	unsigned int pre_div, pwm_div, best_pre_div, best_pwm_div;
>>>> +	unsigned long rate = clk_get_rate(ipq_chip->clk);
>>>> +	u64 period_ns, duty_ns, period_rate;
>>>> +	u64 min_diff;
>>>> +
>>>> +	if (state->polarity != PWM_POLARITY_NORMAL)
>>>> +		return -EINVAL;
>>>> +
>>>> +	if (state->period < DIV64_U64_ROUND_UP(NSEC_PER_SEC, rate))
>>>> +		return -ERANGE;
>>>> +
>>>> +	period_ns = min(state->period, IPQ_PWM_MAX_PERIOD_NS);
>>>> +	duty_ns = min(state->duty_cycle, period_ns);
>>>> +
>>>> +	/*
>>>> +	 * period_ns is 1G or less. As long as rate is less than 16 GHz,
>>>> +	 * period_rate does not overflow. Make that explicit.
>>>> +	 */
>>>> +	if (rate > 16ULL * GIGA)
>>>> +		return -EINVAL;
>>>> +	period_rate = period_ns * rate;
>>>> +	best_pre_div = IPQ_PWM_MAX_DIV;
>>>> +	best_pwm_div = IPQ_PWM_MAX_DIV;
>>>> +	/*
>>>> +	 * We don't need to consider pre_div values smaller than
>>>> +	 *
>>>> +	 *                              period_rate
>>>> +	 *  pre_div_min := ------------------------------------
>>>> +	 *                 NSEC_PER_SEC * (IPQ_PWM_MAX_DIV + 1)
>>>> +	 *
>>>> +	 * because pre_div = pre_div_min results in a better
>>>> +	 * approximation.
>>>> +	 */
>>>> +	pre_div = div64_u64(period_rate,
>>>> +			(u64)NSEC_PER_SEC * (IPQ_PWM_MAX_DIV + 1));
>>>> +	min_diff = period_rate;
>>>> +
>>>> +	for (; pre_div <= IPQ_PWM_MAX_DIV; pre_div++) {
>>>> +		u64 remainder;
>>>> +
>>>> +		pwm_div = div64_u64_rem(period_rate,
>>>> +				(u64)NSEC_PER_SEC * (pre_div + 1), &remainder);
>>>> +		/* pwm_div is unsigned; the check below catches underflow */
>>>> +		pwm_div--;
>>>> +
>>>> +		/*
>>>> +		 * Swapping values for pre_div and pwm_div produces the same
>>>> +		 * period length. So we can skip all settings with pre_div >
>>>> +		 * pwm_div which results in bigger constraints for selecting
>>>> +		 * the duty_cycle than with the two values swapped.
>>>> +		 */
>>>> +		if (pre_div > pwm_div)
>>>> +			break;
>>>> +
>>>> +		/*
>>>> +		 * Make sure we can do 100% duty cycle where
>>>> +		 * hi_dur == pwm_div + 1
>>>> +		 */
>>>> +		if (pwm_div > IPQ_PWM_MAX_DIV - 1)
>>>> +			continue;
>>>> +
>>>> +		if (remainder < min_diff) {
>>>> +			best_pre_div = pre_div;
>>>> +			best_pwm_div = pwm_div;
>>>> +			min_diff = remainder;
>>>> +
>>>> +			if (min_diff == 0) /* bingo */
>>>> +				break;
>>>> +		}
>>>> +	}
>>>> +
>>>> +	/* config divider values for the closest possible frequency */
>>>> +	config_div_and_duty(pwm, best_pre_div, best_pwm_div,
>>>> +			    rate, duty_ns, state->enabled);
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static void ipq_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
>>>> +			      struct pwm_state *state)
>>>> +{
>>>> +	struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(chip);
>>>> +	unsigned long rate = clk_get_rate(ipq_chip->clk);
>>>> +	unsigned int pre_div, pwm_div, hi_dur;
>>>> +	u64 effective_div, hi_div;
>>>> +	u32 reg0, reg1;
>>>> +
>>>> +	reg0 = ipq_pwm_reg_read(pwm, IPQ_PWM_REG0);
>>>> +	reg1 = ipq_pwm_reg_read(pwm, IPQ_PWM_REG1);
>>>> +
>>>> +	state->polarity = PWM_POLARITY_NORMAL;
>>>> +	state->enabled = reg1 & IPQ_PWM_REG1_ENABLE;
>>>> +
>>>> +	pwm_div = FIELD_GET(IPQ_PWM_REG0_PWM_DIV, reg0);
>>>> +	hi_dur = FIELD_GET(IPQ_PWM_REG0_HI_DURATION, reg0);
>>>> +	pre_div = FIELD_GET(IPQ_PWM_REG1_PRE_DIV, reg1);
>>>> +
>>>> +	/* No overflow here, both pre_div and pwm_div <= 0xffff */
>>>> +	effective_div = (u64)(pre_div + 1) * (pwm_div + 1);
>>>> +	state->period = DIV64_U64_ROUND_UP(effective_div * NSEC_PER_SEC, rate);
>>>> +
>>>> +	hi_div = hi_dur * (pre_div + 1);
>>>> +	state->duty_cycle = DIV64_U64_ROUND_UP(hi_div * NSEC_PER_SEC, rate);
>>>> +}
>>>> +
>>>> +static const struct pwm_ops ipq_pwm_ops = {
>>>> +	.apply = ipq_pwm_apply,
>>>> +	.get_state = ipq_pwm_get_state,
>>>> +	.owner = THIS_MODULE,
>>>> +};
>>>> +
>>>> +static int ipq_pwm_probe(struct platform_device *pdev)
>>>> +{
>>>> +	struct ipq_pwm_chip *pwm;
>>>> +	struct device *dev = &pdev->dev;
>>>> +	int ret;
>>>> +
>>>> +	pwm = devm_kzalloc(dev, sizeof(*pwm), GFP_KERNEL);
>>>> +	if (!pwm)
>>>> +		return -ENOMEM;
>>>> +
>>>> +	platform_set_drvdata(pdev, pwm);
>>>> +
>>>> +	pwm->mem = devm_platform_ioremap_resource(pdev, 0);
>>>> +	if (IS_ERR(pwm->mem))
>>>> +		return dev_err_probe(dev, PTR_ERR(pwm->mem),
>>>> +				"regs map failed");
>>>> +
>>>> +	pwm->clk = devm_clk_get(dev, NULL);
>>>> +	if (IS_ERR(pwm->clk))
>>>> +		return dev_err_probe(dev, PTR_ERR(pwm->clk),
>>>> +				"failed to get clock");
>>>> +
>>>> +	ret = clk_prepare_enable(pwm->clk);
>>>> +	if (ret)
>>>> +		return dev_err_probe(dev, ret, "clock enable failed");
>>>> +
>>>> +	pwm->chip.dev = dev;
>>>> +	pwm->chip.ops = &ipq_pwm_ops;
>>>> +	pwm->chip.npwm = 4;
>>>> +
>>>> +	ret = pwmchip_add(&pwm->chip);
>>>> +	if (ret < 0) {
>>>> +		dev_err_probe(dev, ret, "pwmchip_add() failed\n");
>>>> +		clk_disable_unprepare(pwm->clk);
>>>> +	}
>>>> +
>>>> +	return ret;
>>>> +}
>>>> +
>>>> +static int ipq_pwm_remove(struct platform_device *pdev)
>>>> +{
>>>> +	struct ipq_pwm_chip *pwm = platform_get_drvdata(pdev);
>>>> +
>>>> +	pwmchip_remove(&pwm->chip);
>>>> +	clk_disable_unprepare(pwm->clk);
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static const struct of_device_id pwm_ipq_dt_match[] = {
>>>> +	{ .compatible = "qcom,ipq6018-pwm", },
>>>> +	{}
>>>> +};
>>>> +MODULE_DEVICE_TABLE(of, pwm_ipq_dt_match);
>>>> +
>>>> +static struct platform_driver ipq_pwm_driver = {
>>>> +	.driver = {
>>>> +		.name = "ipq-pwm",
>>>> +		.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");
>> 


-- 
                                                     ~. .~   Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
   - baruch@tkos.co.il - tel: +972.52.368.4656, http://www.tkos.co.il -