Message-ID: <BYAPR02MB4278A250C64CEEAED222A785A1759@BYAPR02MB4278.namprd02.prod.outlook.com>
Date:   Tue, 14 Dec 2021 09:08:09 +0000
From:   Mubin Usman Sayyed <MUBINUSM@...inx.com>
To:     Michal Simek <monstr@...str.eu>,
        Sean Anderson <sean.anderson@...o.com>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Thierry Reding <thierry.reding@...il.com>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Alvaro Gamez <alvaro.gamez@...ent.com>,
        Lee Jones <lee.jones@...aro.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Michal Simek <michals@...inx.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v11 2/2] pwm: Add support for Xilinx AXI Timer

Hi Sean,

> -----Original Message-----
> From: Michal Simek <monstr@...str.eu>
> Sent: Tuesday, December 14, 2021 1:38 PM
> To: Sean Anderson <sean.anderson@...o.com>; linux-
> pwm@...r.kernel.org; devicetree@...r.kernel.org; Thierry Reding
> <thierry.reding@...il.com>
> Cc: linux-arm-kernel@...ts.infradead.org; Alvaro Gamez
> <alvaro.gamez@...ent.com>; Lee Jones <lee.jones@...aro.org>; Uwe
> Kleine-König <u.kleine-koenig@...gutronix.de>; Michal Simek
> <michals@...inx.com>; linux-kernel@...r.kernel.org; Mubin Usman Sayyed
> <MUBINUSM@...inx.com>
> Subject: Re: [PATCH v11 2/2] pwm: Add support for Xilinx AXI Timer
> 
> +Mubin
> 
> On 11/24/21 00:25, Sean Anderson wrote:
> > This adds PWM support for Xilinx LogiCORE IP AXI soft timers commonly
> > found on Xilinx FPGAs. At the moment clock control is very basic: we
> > just enable the clock during probe and pin the frequency. In the
> > future, someone could add support for disabling the clock when not in use.
> >
> > Some common code has been specially demarcated. While currently only
> > used by the PWM driver, it is anticipated that it may be split off in
> > the future to be used by the timer driver as well.
> >
> > This driver was written with reference to Xilinx DS764 for v1.03.a [1].
> >
> > [1]
> >
> https://www.xilinx.com/support/documentation/ip_documentation/axi_tim
> e
> > r/v1_03_a/axi_timer_ds764.pdf
> >
> > Signed-off-by: Sean Anderson <sean.anderson@...o.com>
> > Acked-by: Michal Simek <michal.simek@...inx.com>
> > ---
> >
> > Changes in v11:
> > - Add comment about why we test for #pwm-cells
> > - Clarify comment on generate out signal
> > - Rename pwm variables to xilinx_pwm
> > - Round like Uwe wants...
> > - s/xilinx_timer/xilinx_pwm/ for non-common functions
> >
> > Changes in v10:
> > - Fix compilation error in timer driver
> >
> > Changes in v9:
> > - Refactor "if { return } else if { }" to "if { return } if { }"
> > - Remove drivers/clocksource/timer-xilinx-common.c from MAINTAINERS
> > - Remove xilinx_timer_common_init and integrate it into
> > xilinx_timer_probe
> >
> > Changes in v8:
> > - Drop new timer driver; it has been deferred for future series
> >
> > Changes in v7:
> > - Add dependency on OF_ADDRESS
> > - Fix period_cycles calculation
> > - Fix typo in limitations
> >
> > Changes in v6:
> > - Capitalize error messages
> > - Don't disable regmap locking to allow inspection of registers via
> >    debugfs
> > - Prevent overflow when calculating period_cycles
> > - Remove enabled variable from xilinx_pwm_apply
> > - Swap order of period_cycle range comparisons
> >
> > Changes in v5:
> > - Allow non-zero #pwm-cells
> > - Correctly set duty_cycle in get_state when TLR0=TLR1
> > - Elaborate on limitation section
> > - Perform some additional checks/rounding in apply_state
> > - Remove xlnx,axi-timer-2.0 compatible string
> > - Rework duty-cycle and period calculations with feedback from Uwe
> > - Switch to regmap to abstract endianness issues
> > - Use more verbose error messages
> >
> > Changes in v4:
> > - Don't use volatile in read/write replacements. Some arches have it and
> >    some don't.
> > - Put common timer properties into their own struct to better reuse
> >    code.
> > - Remove references to properties which are not good enough for Linux.
> >
> > Changes in v3:
> > - Add clockevent and clocksource support
> > - Remove old microblaze driver
> > - Rewrite probe to only use a device_node, since timers may need to be
> >    initialized before we have proper devices. This does bloat the code a bit
> >    since we can no longer rely on helpers such as dev_err_probe. We also
> >    cannot rely on device resources being free'd on failure, so we must free
> >    them manually.
> > - We now access registers through xilinx_timer_(read|write). This allows us
> >    to deal with endianness issues, as originally seen in the microblaze
> >    driver. CAVEAT EMPTOR: I have not tested this on big-endian!
> >
> > Changes in v2:
> > - Add comment describing device
> > - Add comment explaining why we depend on !MICROBLAZE
> > - Add dependencies on COMMON_CLK and HAS_IOMEM
> > - Cast dividends to u64 to avoid overflow
> > - Check for over- and underflow when calculating TLR
> > - Check range of xlnx,count-width
> > - Don't compile this module by default for arm64
> > - Don't set pwmchip.base to -1
> > - Ensure the clock is always running when the pwm is registered
> > - Remove debugfs file :l
> > - Rename TCSR_(SET|CLEAR) to TCSR_RUN_(SET|CLEAR)
> > - Report errors with dev_error_probe
> > - Set xilinx_pwm_ops.owner
> > - Use NSEC_TO_SEC instead of defining our own
> > - Use TCSR_RUN_MASK to check if the PWM is enabled, as suggested by
> > Uwe
> >
> >   MAINTAINERS                        |   6 +
> >   arch/microblaze/kernel/timer.c     |   3 +
> >   drivers/pwm/Kconfig                |  14 ++
> >   drivers/pwm/Makefile               |   1 +
> >   drivers/pwm/pwm-xilinx.c           | 318 +++++++++++++++++++++++++++++
> >   include/clocksource/timer-xilinx.h |  91 +++++++++
> >   6 files changed, 433 insertions(+)
> >   create mode 100644 drivers/pwm/pwm-xilinx.c
> >   create mode 100644 include/clocksource/timer-xilinx.h
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS index
> > 5250298d2817..b2b3ce106e99 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -20897,6 +20897,12 @@ F:	drivers/misc/Makefile
> >   F:	drivers/misc/xilinx_sdfec.c
> >   F:	include/uapi/misc/xilinx_sdfec.h
> >
> > +XILINX PWM DRIVER
> > +M:	Sean Anderson <sean.anderson@...o.com>
> > +S:	Maintained
> > +F:	drivers/pwm/pwm-xilinx.c
> > +F:	include/clocksource/timer-xilinx.h
> > +
> >   XILINX UARTLITE SERIAL DRIVER
> >   M:	Peter Korsgaard <jacmet@...site.dk>
> >   L:	linux-serial@...r.kernel.org
> > diff --git a/arch/microblaze/kernel/timer.c
> > b/arch/microblaze/kernel/timer.c index f8832cf49384..dea34a3d4aa4
> > 100644
> > --- a/arch/microblaze/kernel/timer.c
> > +++ b/arch/microblaze/kernel/timer.c
> > @@ -251,6 +251,9 @@ static int __init xilinx_timer_init(struct device_node
> *timer)
> >   	u32 timer_num = 1;
> >   	int ret;
> >
> > +	if (of_property_read_bool(timer, "#pwm-cells"))
> > +		return 0;
[Mubin]:  Can you please return  -ENODEV here,  PWM driver would not be probed if return value is 0.

Thanks,
Mubin
> > +
> >   	if (initialized)
> >   		return -EINVAL;
> >
> > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig index
> > 21e3b05a5153..cefbf00b4c7e 100644
> > --- a/drivers/pwm/Kconfig
> > +++ b/drivers/pwm/Kconfig
> > @@ -640,4 +640,18 @@ config PWM_VT8500
> >   	  To compile this driver as a module, choose M here: the module
> >   	  will be called pwm-vt8500.
> >
> > +config PWM_XILINX
> > +	tristate "Xilinx AXI Timer PWM support"
> > +	depends on OF_ADDRESS
> > +	depends on COMMON_CLK
> > +	select REGMAP_MMIO
> > +	help
> > +	  PWM driver for Xilinx LogiCORE IP AXI timers. This timer is
> > +	  typically a soft core which may be present in Xilinx FPGAs.
> > +	  This device may also be present in Microblaze soft processors.
> > +	  If you don't have this IP in your design, choose N.
> > +
> > +	  To compile this driver as a module, choose M here: the module
> > +	  will be called pwm-xilinx.
> > +
> >   endif
> > diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile index
> > 708840b7fba8..ea785480359b 100644
> > --- a/drivers/pwm/Makefile
> > +++ b/drivers/pwm/Makefile
> > @@ -60,3 +60,4 @@ obj-$(CONFIG_PWM_TWL)		+= pwm-twl.o
> >   obj-$(CONFIG_PWM_TWL_LED)	+= pwm-twl-led.o
> >   obj-$(CONFIG_PWM_VISCONTI)	+= pwm-visconti.o
> >   obj-$(CONFIG_PWM_VT8500)	+= pwm-vt8500.o
> > +obj-$(CONFIG_PWM_XILINX)	+= pwm-xilinx.o
> > diff --git a/drivers/pwm/pwm-xilinx.c b/drivers/pwm/pwm-xilinx.c new
> > file mode 100644 index 000000000000..b64735880c4c
> > --- /dev/null
> > +++ b/drivers/pwm/pwm-xilinx.c
> > @@ -0,0 +1,318 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Copyright (C) 2021 Sean Anderson <sean.anderson@...o.com>
> > + *
> > + * Limitations:
> > + * - When changing both duty cycle and period, we may end up with one
> cycle
> > + *   with the old duty cycle and the new period. This is because the
> counters
> > + *   may only be reloaded by first stopping them, or by letting them be
> > + *   automatically reloaded at the end of a cycle. If this automatic reload
> > + *   happens after we set TLR0 but before we set TLR1 then we will have a
> > + *   bad cycle. This could probably be fixed by reading TCR0 just before
> > + *   reprogramming, but I think it would add complexity for little gain.
> > + * - Cannot produce 100% duty cycle by configuring the TLRs. This might be
> > + *   possible by stopping the counters at an appropriate point in the cycle,
> > + *   but this is not (yet) implemented.
> > + * - Only produces "normal" output.
> > + * - Always produces low output if disabled.
> > + */
> > +
> > +#include <clocksource/timer-xilinx.h> #include <linux/clk.h> #include
> > +<linux/clk-provider.h> #include <linux/device.h> #include
> > +<linux/module.h> #include <linux/of.h> #include
> > +<linux/platform_device.h> #include <linux/pwm.h> #include
> > +<linux/regmap.h>
> > +
> > +/*
> > + * The following functions are "common" to drivers for this device,
> > +and may be
> > + * exported at a future date.
> > + */
> > +u32 xilinx_timer_tlr_cycles(struct xilinx_timer_priv *priv, u32 tcsr,
> > +			    u64 cycles)
> > +{
> > +	WARN_ON(cycles < 2 || cycles - 2 > priv->max);
> > +
> > +	if (tcsr & TCSR_UDT)
> > +		return cycles - 2;
> > +	return priv->max - cycles + 2;
> > +}
> > +
> > +unsigned int xilinx_timer_get_period(struct xilinx_timer_priv *priv,
> > +				     u32 tlr, u32 tcsr)
> > +{
> > +	u64 cycles;
> > +
> > +	if (tcsr & TCSR_UDT)
> > +		cycles = tlr + 2;
> > +	else
> > +		cycles = (u64)priv->max - tlr + 2;
> > +
> > +	/* cycles has a max of 2^32 + 2 */
> > +	return DIV64_U64_ROUND_UP(cycles * NSEC_PER_SEC,
> > +				  clk_get_rate(priv->clk));
> > +}
> > +
> > +/*
> > + * The idea here is to capture whether the PWM is actually running (e.g.
> > + * because we or the bootloader set it up) and we need to be careful
> > +to ensure
> > + * we don't cause a glitch. According to the data sheet, to enable
> > +the PWM we
> > + * need to
> > + *
> > + * - Set both timers to generate mode (MDT=1)
> > + * - Set both timers to PWM mode (PWMA=1)
> > + * - Enable the generate out signals (GENT=1)
> > + *
> > + * In addition,
> > + *
> > + * - The timer must be running (ENT=1)
> > + * - The timer must auto-reload TLR into TCR (ARHT=1)
> > + * - We must not be in the process of loading TLR into TCR (LOAD=0)
> > + * - Cascade mode must be disabled (CASC=0)
> > + *
> > + * If any of these differ from usual, then the PWM is either
> > +disabled, or is
> > + * running in a mode that this driver does not support.
> > + */
> > +#define TCSR_PWM_SET (TCSR_GENT | TCSR_ARHT | TCSR_ENT |
> TCSR_PWMA)
> > +#define TCSR_PWM_CLEAR (TCSR_MDT | TCSR_LOAD) #define
> TCSR_PWM_MASK
> > +(TCSR_PWM_SET | TCSR_PWM_CLEAR)
> > +
> > +struct xilinx_pwm_device {
> > +	struct pwm_chip chip;
> > +	struct xilinx_timer_priv priv;
> > +};
> > +
> > +static inline struct xilinx_timer_priv
> > +*xilinx_pwm_chip_to_priv(struct pwm_chip *chip) {
> > +	return &container_of(chip, struct xilinx_pwm_device, chip)->priv; }
> > +
> > +static bool xilinx_timer_pwm_enabled(u32 tcsr0, u32 tcsr1) {
> > +	return ((TCSR_PWM_MASK | TCSR_CASC) & tcsr0) ==
> TCSR_PWM_SET &&
> > +		(TCSR_PWM_MASK & tcsr1) == TCSR_PWM_SET; }
> > +
> > +static int xilinx_pwm_apply(struct pwm_chip *chip, struct pwm_device
> *unused,
> > +			    const struct pwm_state *state) {
> > +	struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip);
> > +	u32 tlr0, tlr1, tcsr0, tcsr1;
> > +	u64 period_cycles, duty_cycles;
> > +	unsigned long rate;
> > +
> > +	if (state->polarity != PWM_POLARITY_NORMAL)
> > +		return -EINVAL;
> > +
> > +	/*
> > +	 * To be representable by TLR, cycles must be between 2 and
> > +	 * priv->max + 2. To enforce this we can reduce the duty
> > +	 * cycle, but we may not increase it.
> > +	 */
> > +	rate = clk_get_rate(priv->clk);
> > +	/* Avoid overflow */
> > +	period_cycles = min_t(u64, state->period, ULONG_MAX *
> NSEC_PER_SEC);
> > +	period_cycles = mul_u64_u32_div(period_cycles, rate,
> NSEC_PER_SEC);
> > +	/* Clamp it for Uwe */
> > +	period_cycles = min_t(u64, period_cycles, priv->max + 2);
> > +	if (period_cycles < 2)
> > +		return -ERANGE;
> > +
> > +	/* Same thing for duty cycles */
> > +	duty_cycles = min_t(u64, state->duty_cycle, ULONG_MAX *
> NSEC_PER_SEC);
> > +	duty_cycles = mul_u64_u32_div(duty_cycles, rate, NSEC_PER_SEC);
> > +	duty_cycles = min_t(u64, duty_cycles, priv->max + 2);
> > +
> > +	/*
> > +	 * If we specify 100% duty cycle, we will get 0% instead, so decrease
> > +	 * the duty cycle count by one.
> > +	 */
> > +	if (duty_cycles >= period_cycles)
> > +		duty_cycles = period_cycles - 1;
> > +
> > +	/* Round down to 0% duty cycle for unrepresentable duty cycles */
> > +	if (duty_cycles < 2)
> > +		duty_cycles = period_cycles;
> > +
> > +	regmap_read(priv->map, TCSR0, &tcsr0);
> > +	regmap_read(priv->map, TCSR1, &tcsr1);
> > +	tlr0 = xilinx_timer_tlr_cycles(priv, tcsr0, period_cycles);
> > +	tlr1 = xilinx_timer_tlr_cycles(priv, tcsr1, duty_cycles);
> > +	regmap_write(priv->map, TLR0, tlr0);
> > +	regmap_write(priv->map, TLR1, tlr1);
> > +
> > +	if (state->enabled) {
> > +		/*
> > +		 * If the PWM is already running, then the counters will be
> > +		 * reloaded at the end of the current cycle.
> > +		 */
> > +		if (!xilinx_timer_pwm_enabled(tcsr0, tcsr1)) {
> > +			/* Load TLR into TCR */
> > +			regmap_write(priv->map, TCSR0, tcsr0 |
> TCSR_LOAD);
> > +			regmap_write(priv->map, TCSR1, tcsr1 |
> TCSR_LOAD);
> > +			/* Enable timers all at once with ENALL */
> > +			tcsr0 = (TCSR_PWM_SET & ~TCSR_ENT) | (tcsr0 &
> TCSR_UDT);
> > +			tcsr1 = TCSR_PWM_SET | TCSR_ENALL | (tcsr1 &
> TCSR_UDT);
> > +			regmap_write(priv->map, TCSR0, tcsr0);
> > +			regmap_write(priv->map, TCSR1, tcsr1);
> > +		}
> > +	} else {
> > +		regmap_write(priv->map, TCSR0, 0);
> > +		regmap_write(priv->map, TCSR1, 0);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static void xilinx_pwm_get_state(struct pwm_chip *chip,
> > +				 struct pwm_device *unused,
> > +				 struct pwm_state *state)
> > +{
> > +	struct xilinx_timer_priv *priv = xilinx_pwm_chip_to_priv(chip);
> > +	u32 tlr0, tlr1, tcsr0, tcsr1;
> > +
> > +	regmap_read(priv->map, TLR0, &tlr0);
> > +	regmap_read(priv->map, TLR1, &tlr1);
> > +	regmap_read(priv->map, TCSR0, &tcsr0);
> > +	regmap_read(priv->map, TCSR1, &tcsr1);
> > +	state->period = xilinx_timer_get_period(priv, tlr0, tcsr0);
> > +	state->duty_cycle = xilinx_timer_get_period(priv, tlr1, tcsr1);
> > +	state->enabled = xilinx_timer_pwm_enabled(tcsr0, tcsr1);
> > +	state->polarity = PWM_POLARITY_NORMAL;
> > +
> > +	/* 100% duty cycle results in constant low output */
> > +	if (state->period == state->duty_cycle)
> > +		state->duty_cycle = 0;
> > +}
> > +
> > +static const struct pwm_ops xilinx_pwm_ops = {
> > +	.apply = xilinx_pwm_apply,
> > +	.get_state = xilinx_pwm_get_state,
> > +	.owner = THIS_MODULE,
> > +};
> > +
> > +static const struct regmap_config xilinx_pwm_regmap_config = {
> > +	.reg_bits = 32,
> > +	.reg_stride = 4,
> > +	.val_bits = 32,
> > +	.val_format_endian = REGMAP_ENDIAN_LITTLE,
> > +	.max_register = TCR1,
> > +};
> > +
> > +static int xilinx_pwm_probe(struct platform_device *pdev) {
> > +	int ret;
> > +	struct device *dev = &pdev->dev;
> > +	struct device_node *np = dev->of_node;
> > +	struct xilinx_timer_priv *priv;
> > +	struct xilinx_pwm_device *xilinx_pwm;
> > +	u32 pwm_cells, one_timer, width;
> > +	void __iomem *regs;
> > +
> > +	/* If there are no PWM cells, this binding is for a timer */
> > +	ret = of_property_read_u32(np, "#pwm-cells", &pwm_cells);
> > +	if (ret == -EINVAL)
> > +		return -ENODEV;
> > +	if (ret)
> > +		return dev_err_probe(dev, ret, "could not read #pwm-
> cells\n");
> > +
> > +	xilinx_pwm = devm_kzalloc(dev, sizeof(*xilinx_pwm), GFP_KERNEL);
> > +	if (!xilinx_pwm)
> > +		return -ENOMEM;
> > +	platform_set_drvdata(pdev, xilinx_pwm);
> > +	priv = &xilinx_pwm->priv;
> > +
> > +	regs = devm_platform_ioremap_resource(pdev, 0);
> > +	if (IS_ERR(regs))
> > +		return PTR_ERR(regs);
> > +
> > +	priv->map = devm_regmap_init_mmio(dev, regs,
> > +					  &xilinx_pwm_regmap_config);
> > +	if (IS_ERR(priv->map))
> > +		return dev_err_probe(dev, PTR_ERR(priv->map),
> > +				     "Could not create regmap\n");
> > +
> > +	ret = of_property_read_u32(np, "xlnx,one-timer-only", &one_timer);
> > +	if (ret)
> > +		return dev_err_probe(dev, ret,
> > +				     "Could not read xlnx,one-timer-only\n");
> > +
> > +	if (one_timer)
> > +		return dev_err_probe(dev, -EINVAL,
> > +				     "Two timers required for PWM mode\n");
> > +
> > +
> > +	ret = of_property_read_u32(np, "xlnx,count-width", &width);
> > +	if (ret == -EINVAL)
> > +		width = 32;
> > +	else if (ret)
> > +		return dev_err_probe(dev, ret,
> > +				     "Could not read xlnx,count-width\n");
> > +
> > +	if (width != 8 && width != 16 && width != 32)
> > +		return dev_err_probe(dev, -EINVAL,
> > +				     "Invalid counter width %d\n", width);
> > +	priv->max = BIT_ULL(width) - 1;
> > +
> > +	/*
> > +	 * The polarity of the Generate Out signals must be active high for
> PWM
> > +	 * mode to work. We could determine this from the device tree, but
> > +	 * alas, such properties are not allowed to be used.
> > +	 */
> > +
> > +	priv->clk = devm_clk_get(dev, "s_axi_aclk");
> > +	if (IS_ERR(priv->clk))
> > +		return dev_err_probe(dev, PTR_ERR(priv->clk),
> > +				     "Could not get clock\n");
> > +
> > +	ret = clk_prepare_enable(priv->clk);
> > +	if (ret)
> > +		return dev_err_probe(dev, ret, "Clock enable failed\n");
> > +	clk_rate_exclusive_get(priv->clk);
> > +
> > +	xilinx_pwm->chip.dev = dev;
> > +	xilinx_pwm->chip.ops = &xilinx_pwm_ops;
> > +	xilinx_pwm->chip.npwm = 1;
> > +	ret = pwmchip_add(&xilinx_pwm->chip);
> > +	if (ret) {
> > +		clk_rate_exclusive_put(priv->clk);
> > +		clk_disable_unprepare(priv->clk);
> > +		return dev_err_probe(dev, ret, "Could not register PWM
> chip\n");
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int xilinx_pwm_remove(struct platform_device *pdev) {
> > +	struct xilinx_pwm_device *xilinx_pwm =
> platform_get_drvdata(pdev);
> > +
> > +	pwmchip_remove(&xilinx_pwm->chip);
> > +	clk_rate_exclusive_put(xilinx_pwm->priv.clk);
> > +	clk_disable_unprepare(xilinx_pwm->priv.clk);
> > +	return 0;
> > +}
> > +
> > +static const struct of_device_id xilinx_pwm_of_match[] = {
> > +	{ .compatible = "xlnx,xps-timer-1.00.a", },
> > +	{},
> > +};
> > +MODULE_DEVICE_TABLE(of, xilinx_pwm_of_match);
> > +
> > +static struct platform_driver xilinx_pwm_driver = {
> > +	.probe = xilinx_pwm_probe,
> > +	.remove = xilinx_pwm_remove,
> > +	.driver = {
> > +		.name = "xilinx-pwm",
> > +		.of_match_table = of_match_ptr(xilinx_pwm_of_match),
> > +	},
> > +};
> > +module_platform_driver(xilinx_pwm_driver);
> > +
> > +MODULE_ALIAS("platform:xilinx-pwm");
> > +MODULE_DESCRIPTION("PWM driver for Xilinx LogiCORE IP AXI Timer");
> > +MODULE_LICENSE("GPL v2");
> > diff --git a/include/clocksource/timer-xilinx.h
> > b/include/clocksource/timer-xilinx.h
> > new file mode 100644
> > index 000000000000..1f7757b84a5e
> > --- /dev/null
> > +++ b/include/clocksource/timer-xilinx.h
> > @@ -0,0 +1,91 @@
> > +/* SPDX-License-Identifier: GPL-2.0+ */
> > +/*
> > + * Copyright (C) 2021 Sean Anderson <sean.anderson@...o.com>  */
> > +
> > +#ifndef XILINX_TIMER_H
> > +#define XILINX_TIMER_H
> > +
> > +#include <linux/compiler.h>
> > +
> > +#define TCSR0	0x00
> > +#define TLR0	0x04
> > +#define TCR0	0x08
> > +#define TCSR1	0x10
> > +#define TLR1	0x14
> > +#define TCR1	0x18
> > +
> > +#define TCSR_MDT	BIT(0)
> > +#define TCSR_UDT	BIT(1)
> > +#define TCSR_GENT	BIT(2)
> > +#define TCSR_CAPT	BIT(3)
> > +#define TCSR_ARHT	BIT(4)
> > +#define TCSR_LOAD	BIT(5)
> > +#define TCSR_ENIT	BIT(6)
> > +#define TCSR_ENT	BIT(7)
> > +#define TCSR_TINT	BIT(8)
> > +#define TCSR_PWMA	BIT(9)
> > +#define TCSR_ENALL	BIT(10)
> > +#define TCSR_CASC	BIT(11)
> > +
> > +struct clk;
> > +struct device_node;
> > +struct regmap;
> > +
> > +/**
> > + * struct xilinx_timer_priv - Private data for Xilinx AXI timer
> > +drivers
> > + * @map: Regmap of the device, possibly with an offset
> > + * @clk: Parent clock
> > + * @max: Maximum value of the counters  */ struct xilinx_timer_priv {
> > +	struct regmap *map;
> > +	struct clk *clk;
> > +	u32 max;
> > +};
> > +
> > +/**
> > + * xilinx_timer_tlr_cycles() - Calculate the TLR for a period specified
> > + *                             in clock cycles
> > + * @priv: The timer's private data
> > + * @tcsr: The value of the TCSR register for this counter
> > + * @cycles: The number of cycles in this period
> > + *
> > + * Callers of this function MUST ensure that @cycles is representable
> > +as
> > + * a TLR.
> > + *
> > + * Return: The calculated value for TLR  */
> > +u32 xilinx_timer_tlr_cycles(struct xilinx_timer_priv *priv, u32 tcsr,
> > +			    u64 cycles);
> > +
> > +/**
> > + * xilinx_timer_get_period() - Get the current period of a counter
> > + * @priv: The timer's private data
> > + * @tlr: The value of TLR for this counter
> > + * @tcsr: The value of TCSR for this counter
> > + *
> > + * Return: The period, in ns
> > + */
> > +unsigned int xilinx_timer_get_period(struct xilinx_timer_priv *priv,
> > +				     u32 tlr, u32 tcsr);
> > +
> > +/**
> > + * xilinx_timer_common_init() - Perform common initialization for Xilinx
> > + *                              AXI timer drivers.
> > + * @priv: The timer's private data
> > + * @np: The devicetree node for the timer
> > + * @one_timer: Set to %1 if there is only one timer
> > + *
> > + * This performs common initialization, such as detecting endianness,
> > + * and parsing devicetree properties. @priv->regs must be initialized
> > + * before calling this function. This function initializes
> > +@...v->read,
> > + * @priv->write, and @priv->width.
> > + *
> > + * Return: 0, or negative errno
> > + */
> > +int xilinx_timer_common_init(struct device_node *np,
> > +			     struct xilinx_timer_priv *priv,
> > +			     u32 *one_timer);
> > +
> > +#endif /* XILINX_TIMER_H */
> 
> --
> Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
> w: www.monstr.eu p: +42-0-721842854
> Maintainer of Linux kernel - Xilinx Microblaze Maintainer of Linux kernel -
> Xilinx Zynq ARM and ZynqMP ARM64 SoCs U-Boot custodian - Xilinx
> Microblaze/Zynq/ZynqMP/Versal SoCs

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