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Date: Mon, 17 Jul 2017 19:33:21 +0100
From: Lee Jones <lee.jones@...aro.org>
To: Fabrice Gasnier <fabrice.gasnier@...com>
Cc: benjamin.gaignard@...aro.org, jic23@...nel.org,
thierry.reding@...il.com, robh+dt@...nel.org, mark.rutland@....com,
alexandre.torgue@...com, mcoquelin.stm32@...il.com,
benjamin.gaignard@...com, linux-iio@...r.kernel.org,
devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org
Subject: Re: [PATCH v3 2/9] mfd: Add STM32 LPTimer driver
On Fri, 07 Jul 2017, Fabrice Gasnier wrote:
> STM32 Low-Power Timer hardware block can be used for:
> - PWM generation
> - IIO trigger (in sync with PWM)
> - IIO quadrature encoder counter
> PWM and IIO timer configuration are mixed in the same registers so
> we need a multi fonction driver to be able to share those registers.
>
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>
For my own reference:
Acked-for-MFD-by: Lee Jones <lee.jones@...aro.org>
> ---
> Changes in v2:
> - Lee's remarks: various comments, max register define, s/Low Power/Low-Power,
> clock name, removed reset, add kernel doc for stm32_lptimer struct
> ---
> drivers/mfd/Kconfig | 14 +++++
> drivers/mfd/Makefile | 1 +
> drivers/mfd/stm32-lptimer.c | 107 ++++++++++++++++++++++++++++++++++++++
> include/linux/mfd/stm32-lptimer.h | 62 ++++++++++++++++++++++
> 4 files changed, 184 insertions(+)
> create mode 100644 drivers/mfd/stm32-lptimer.c
> create mode 100644 include/linux/mfd/stm32-lptimer.h
>
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 3eb5c93..8e1ca44 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -1683,6 +1683,20 @@ config MFD_STW481X
> in various ST Microelectronics and ST-Ericsson embedded
> Nomadik series.
>
> +config MFD_STM32_LPTIMER
> + tristate "Support for STM32 Low-Power Timer"
> + depends on (ARCH_STM32 && OF) || COMPILE_TEST
> + select MFD_CORE
> + select REGMAP
> + select REGMAP_MMIO
> + help
> + Select this option to enable STM32 Low-Power Timer driver
> + used for PWM, IIO Trigger, IIO Encoder and Counter. Shared
> + resources are also dealt with here.
> +
> + To compile this driver as a module, choose M here: the
> + module will be called stm32-lptimer.
> +
> config MFD_STM32_TIMERS
> tristate "Support for STM32 Timers"
> depends on (ARCH_STM32 && OF) || COMPILE_TEST
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index c16bf1e..a5308d8 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -219,5 +219,6 @@ obj-$(CONFIG_MFD_MT6397) += mt6397-core.o
> obj-$(CONFIG_MFD_ALTERA_A10SR) += altera-a10sr.o
> obj-$(CONFIG_MFD_SUN4I_GPADC) += sun4i-gpadc.o
>
> +obj-$(CONFIG_MFD_STM32_LPTIMER) += stm32-lptimer.o
> obj-$(CONFIG_MFD_STM32_TIMERS) += stm32-timers.o
> obj-$(CONFIG_MFD_MXS_LRADC) += mxs-lradc.o
> diff --git a/drivers/mfd/stm32-lptimer.c b/drivers/mfd/stm32-lptimer.c
> new file mode 100644
> index 0000000..075330a
> --- /dev/null
> +++ b/drivers/mfd/stm32-lptimer.c
> @@ -0,0 +1,107 @@
> +/*
> + * STM32 Low-Power Timer parent driver.
> + *
> + * Copyright (C) STMicroelectronics 2017
> + *
> + * Author: Fabrice Gasnier <fabrice.gasnier@...com>
> + *
> + * Inspired by Benjamin Gaignard's stm32-timers driver
> + *
> + * License terms: GNU General Public License (GPL), version 2
> + */
> +
> +#include <linux/mfd/stm32-lptimer.h>
> +#include <linux/module.h>
> +#include <linux/of_platform.h>
> +
> +#define STM32_LPTIM_MAX_REGISTER 0x3fc
> +
> +static const struct regmap_config stm32_lptimer_regmap_cfg = {
> + .reg_bits = 32,
> + .val_bits = 32,
> + .reg_stride = sizeof(u32),
> + .max_register = STM32_LPTIM_MAX_REGISTER,
> +};
> +
> +static int stm32_lptimer_detect_encoder(struct stm32_lptimer *ddata)
> +{
> + u32 val;
> + int ret;
> +
> + /*
> + * Quadrature encoder mode bit can only be written and read back when
> + * Low-Power Timer supports it.
> + */
> + ret = regmap_update_bits(ddata->regmap, STM32_LPTIM_CFGR,
> + STM32_LPTIM_ENC, STM32_LPTIM_ENC);
> + if (ret)
> + return ret;
> +
> + ret = regmap_read(ddata->regmap, STM32_LPTIM_CFGR, &val);
> + if (ret)
> + return ret;
> +
> + ret = regmap_update_bits(ddata->regmap, STM32_LPTIM_CFGR,
> + STM32_LPTIM_ENC, 0);
> + if (ret)
> + return ret;
> +
> + ddata->has_encoder = !!(val & STM32_LPTIM_ENC);
> +
> + return 0;
> +}
> +
> +static int stm32_lptimer_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct stm32_lptimer *ddata;
> + struct resource *res;
> + void __iomem *mmio;
> + int ret;
> +
> + ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
> + if (!ddata)
> + return -ENOMEM;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + mmio = devm_ioremap_resource(dev, res);
> + if (IS_ERR(mmio))
> + return PTR_ERR(mmio);
> +
> + ddata->regmap = devm_regmap_init_mmio_clk(dev, "mux", mmio,
> + &stm32_lptimer_regmap_cfg);
> + if (IS_ERR(ddata->regmap))
> + return PTR_ERR(ddata->regmap);
> +
> + ddata->clk = devm_clk_get(dev, NULL);
> + if (IS_ERR(ddata->clk))
> + return PTR_ERR(ddata->clk);
> +
> + ret = stm32_lptimer_detect_encoder(ddata);
> + if (ret)
> + return ret;
> +
> + platform_set_drvdata(pdev, ddata);
> +
> + return devm_of_platform_populate(&pdev->dev);
> +}
> +
> +static const struct of_device_id stm32_lptimer_of_match[] = {
> + { .compatible = "st,stm32-lptimer", },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, stm32_lptimer_of_match);
> +
> +static struct platform_driver stm32_lptimer_driver = {
> + .probe = stm32_lptimer_probe,
> + .driver = {
> + .name = "stm32-lptimer",
> + .of_match_table = stm32_lptimer_of_match,
> + },
> +};
> +module_platform_driver(stm32_lptimer_driver);
> +
> +MODULE_AUTHOR("Fabrice Gasnier <fabrice.gasnier@...com>");
> +MODULE_DESCRIPTION("STMicroelectronics STM32 Low-Power Timer");
> +MODULE_ALIAS("platform:stm32-lptimer");
> +MODULE_LICENSE("GPL v2");
> diff --git a/include/linux/mfd/stm32-lptimer.h b/include/linux/mfd/stm32-lptimer.h
> new file mode 100644
> index 0000000..77c7cf4
> --- /dev/null
> +++ b/include/linux/mfd/stm32-lptimer.h
> @@ -0,0 +1,62 @@
> +/*
> + * STM32 Low-Power Timer parent driver.
> + *
> + * Copyright (C) STMicroelectronics 2017
> + *
> + * Author: Fabrice Gasnier <fabrice.gasnier@...com>
> + *
> + * Inspired by Benjamin Gaignard's stm32-timers driver
> + *
> + * License terms: GNU General Public License (GPL), version 2
> + */
> +
> +#ifndef _LINUX_STM32_LPTIMER_H_
> +#define _LINUX_STM32_LPTIMER_H_
> +
> +#include <linux/clk.h>
> +#include <linux/regmap.h>
> +
> +#define STM32_LPTIM_ISR 0x00 /* Interrupt and Status Reg */
> +#define STM32_LPTIM_ICR 0x04 /* Interrupt Clear Reg */
> +#define STM32_LPTIM_IER 0x08 /* Interrupt Enable Reg */
> +#define STM32_LPTIM_CFGR 0x0C /* Configuration Reg */
> +#define STM32_LPTIM_CR 0x10 /* Control Reg */
> +#define STM32_LPTIM_CMP 0x14 /* Compare Reg */
> +#define STM32_LPTIM_ARR 0x18 /* Autoreload Reg */
> +#define STM32_LPTIM_CNT 0x1C /* Counter Reg */
> +
> +/* STM32_LPTIM_ISR - bit fields */
> +#define STM32_LPTIM_CMPOK_ARROK GENMASK(4, 3)
> +#define STM32_LPTIM_ARROK BIT(4)
> +#define STM32_LPTIM_CMPOK BIT(3)
> +
> +/* STM32_LPTIM_ICR - bit fields */
> +#define STM32_LPTIM_CMPOKCF_ARROKCF GENMASK(4, 3)
> +
> +/* STM32_LPTIM_CR - bit fields */
> +#define STM32_LPTIM_CNTSTRT BIT(2)
> +#define STM32_LPTIM_ENABLE BIT(0)
> +
> +/* STM32_LPTIM_CFGR - bit fields */
> +#define STM32_LPTIM_ENC BIT(24)
> +#define STM32_LPTIM_COUNTMODE BIT(23)
> +#define STM32_LPTIM_WAVPOL BIT(21)
> +#define STM32_LPTIM_PRESC GENMASK(11, 9)
> +#define STM32_LPTIM_CKPOL GENMASK(2, 1)
> +
> +/* STM32_LPTIM_ARR */
> +#define STM32_LPTIM_MAX_ARR 0xFFFF
> +
> +/**
> + * struct stm32_lptimer - STM32 Low-Power Timer data assigned by parent device
> + * @clk: clock reference for this instance
> + * @regmap: register map reference for this instance
> + * @has_encoder: indicates this Low-Power Timer supports encoder mode
> + */
> +struct stm32_lptimer {
> + struct clk *clk;
> + struct regmap *regmap;
> + bool has_encoder;
> +};
> +
> +#endif
--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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