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From: Baruch Siach <baruch@tkos.co.il>
To: Devi Priya <quic_devipriy@quicinc.com>
Cc: "Thierry Reding" <thierry.reding@gmail.com>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Andy Gross" <agross@kernel.org>,
	"Bjorn Andersson" <bjorn.andersson@linaro.org>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Robert Marko" <robert.marko@sartura.hr>,
	"Kathiravan T" <quic_kathirav@quicinc.com>,
	linux-pwm@vger.kernel.org, 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: Fri, 15 Sep 2023 09:36:10 +0300	[thread overview]
Message-ID: <87wmwsylup.fsf@tarshish> (raw)
In-Reply-To: <8a331c88-c7d4-3a14-0ec3-fd616ea24a99@quicinc.com>

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.

Thanks,
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 -

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  reply	other threads:[~2023-09-15  6:47 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-07  9:30 [PATCH 1/3] pwm: driver for qualcomm ipq6018 pwm block Baruch Siach
2022-02-07  9:30 ` [PATCH 2/3] dt-bindings: pwm: add IPQ6018 binding Baruch Siach
2022-02-24 19:48   ` Bjorn Andersson
2022-02-07  9:30 ` [PATCH 3/3] arm64: dts: ipq6018: add pwm node Baruch Siach
2023-09-15  6:25 ` [PATCH 1/3] pwm: driver for qualcomm ipq6018 pwm block Devi Priya
2023-09-15  6:36   ` Baruch Siach [this message]
2023-09-20  4:58     ` Devi Priya
2023-09-22  6:00     ` Devi Priya
2023-09-22  8:35       ` Baruch Siach
2023-09-22 10:56         ` Devi Priya
  -- strict thread matches above, loose matches on Subject: below --
2021-05-19  7:48 Baruch Siach
2021-05-22 21:35 ` Uwe Kleine-König
2021-05-23 15:54   ` Baruch Siach
2021-05-22 21:37 ` Uwe Kleine-König

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