Message-ID: <20190214093445.GF13737@dell>
Date:   Thu, 14 Feb 2019 09:34:45 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Virendra Kakade <virendra.kakade@...com>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, robh+dt@...nel.org, mark.rutland@....com,
        sre@...nel.org, moritz.fischer@...us.com
Subject: Re: [RFC 2/6] mfd: Support for Ettus Research E31x devices PMU

On Mon, 11 Feb 2019, Virendra Kakade wrote:

> Signed-off-by: Virendra Kakade <virendra.kakade@...com>
> ---
>  drivers/mfd/Kconfig          |  7 +++
>  drivers/mfd/Makefile         |  2 +-
>  drivers/mfd/e31x-pmu.c       | 89 ++++++++++++++++++++++++++++++++++++
>  include/linux/mfd/e31x-pmu.h | 20 ++++++++
>  4 files changed, 117 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/mfd/e31x-pmu.c
>  create mode 100644 include/linux/mfd/e31x-pmu.h
> 
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 8c5dfdce4326..6c4c0747f2a5 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -1916,4 +1916,11 @@ config RAVE_SP_CORE
>  	  device found on several devices in RAVE line of hardware.
>  
>  endmenu
> +
> +config MFD_E31X_PMU
> +	tristate "E31X PMU driver"
> +	select MFD_SYSCON
> +	help
> +	 Select this to get support for the Ettus Research E31x devices.
> +
>  endif
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 12980a4ad460..e37c2057134b 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -241,4 +241,4 @@ obj-$(CONFIG_MFD_MXS_LRADC)     += mxs-lradc.o
>  obj-$(CONFIG_MFD_SC27XX_PMIC)	+= sprd-sc27xx-spi.o
>  obj-$(CONFIG_RAVE_SP_CORE)	+= rave-sp.o
>  obj-$(CONFIG_MFD_ROHM_BD718XX)	+= rohm-bd718x7.o
> -
> +obj-$(CONFIG_MFD_E31X_PMU)      += e31x-pmu.o
> diff --git a/drivers/mfd/e31x-pmu.c b/drivers/mfd/e31x-pmu.c
> new file mode 100644
> index 000000000000..383df68a538f
> --- /dev/null
> +++ b/drivers/mfd/e31x-pmu.c
> @@ -0,0 +1,89 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2018 National Instruments Corp

This is out of date.

'\n' here.

> + * Author: Virendra Kakade<virendra.kakade@...com>

You need a space after your name.

> + * Ettus Research E31x PMU MFD driver

Please expand PMU.

> + */
> +
> +#include <linux/err.h>
> +#include <linux/delay.h>
> +#include <linux/interrupt.h>
> +#include <linux/kernel.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/module.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/regmap.h>
> +#include <linux/mfd/core.h>
> +#include <linux/of_device.h>
> +#include <linux/mfd/e31x-pmu.h>
> +#include <linux/platform_device.h>

Alphabetical.

> +#define E31X_PMU_MISC_IRQ_MASK		BIT(8)
> +#define E31X_PMU_MISC_IRQ_SHIFT		8
> +#define E31X_PMU_MISC_VERSION_MIN_MASK	GENMASK(3, 0)
> +#define E31X_PMU_MISC_VERSION_MIN_SHIFT	0
> +#define E31X_PMU_MISC_VERSION_MAJ_MASK	GENMASK(7, 4)
> +#define E31X_PMU_MISC_VERSION_MAJ_SHIFT	4
> +
> +struct e31x_pmu {
> +	struct regmap *regmap;
> +};

A whole struct for one attribute?

> +static int e31x_pmu_check_version(struct e31x_pmu *pmu)
> +{
> +	int timeout = 100;

Where does 100 come from?

> +	u32 misc, maj;
> +	int err;

'ret' is more common.

> +	/* we need to wait a bit for firmware to populate the fields */

"a bit" ?

What does the datasheet say?

Please use proper grammar.  Capital letters.

> +	while (timeout--) {
> +		err = regmap_read(pmu->regmap, E31X_PMU_REG_MISC, &misc);
> +		if (err)
> +			return err;
> +		if (misc)
> +			break;
> +
> +	usleep_range(2500, 5000);

Formatting.

> +	}
> +
> +	/* only firmware versions above 2.0 are supported */

"Only supports firmware version 2.0 and above"

> +	maj = E31X_PMU_GET_FIELD(MISC_VERSION_MAJ, misc);
> +	if (maj < 2)
> +		return -ENOTSUPP;

'\n' here.

> +	return 0;
> +}
> +
> +static int e31x_pmu_probe(struct platform_device *pdev)
> +{
> +	struct e31x_pmu *pmu;
> +
> +	pmu = devm_kzalloc(&pdev->dev, sizeof(*pmu), GFP_KERNEL);
> +	if (!pmu)
> +		return -ENOMEM;

'\n' here.

> +	pmu->regmap = syscon_regmap_lookup_by_phandle(\

Why are you storing regmap?

Just pass it directly to e31x_pmu_check_version().

> +			pdev->dev.of_node, "regmap");
> +

Remove this line.

> +	if (IS_ERR(pmu->regmap))
> +		return PTR_ERR(pmu->regmap);

'\n' here.

> +	if (e31x_pmu_check_version(pmu))

Please split out the function from the if.

Use a variable 'ret' to feed into and check that.

> +		return -ENOTSUPP;

'\n' here.

> +	return devm_of_platform_populate(&pdev->dev);
> +}
> +
> +static const struct of_device_id e31x_pmu_id[] = {
> +	{ .compatible = "ni,e31x-pmu" },
> +	{},
> +};
> +
> +static struct platform_driver e31x_pmu_driver = {
> +	.driver = {
> +	.name = "e31x-pmu",
> +	.of_match_table = e31x_pmu_id,

These 2 lines need indenting.

> +	},
> +	.probe = e31x_pmu_probe,
> +};
> +module_platform_driver(e31x_pmu_driver);
> +
> +MODULE_DESCRIPTION("E31x PMU driver");
> +MODULE_AUTHOR("Virendra Kakade <virendra.kakade@...com>");
> +MODULE_LICENSE("GPL");

So the whole purpose of this driver is to do a version check.

Seems like over-kill!

Probably better to do the version check in an inline function stored
in a header file, then call it from each of the children's .probe()
function.

> diff --git a/include/linux/mfd/e31x-pmu.h b/include/linux/mfd/e31x-pmu.h
> new file mode 100644
> index 000000000000..c57d5a8c1aad
> --- /dev/null
> +++ b/include/linux/mfd/e31x-pmu.h
> @@ -0,0 +1,20 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2018 National Instruments Corp

Out of date.

'\n' here.

> + * Author: Virendra Kakade <virendra.kakade@...com>
> + *
> + * Ettus Research E31x PMU constants
> + */
> +
> +#ifndef MFD_E31X_PMU_H
> +#define MFD_E31X_PMU_H
> +
> +#include <linux/bitops.h>
> +
> +#define E31X_PMU_REG_MISC      0x04
> +
> +#define E31X_PMU_GET_FIELD(name, reg) \
> +	(((reg) & E31X_PMU_## name ##_MASK) >> \
> +	E31X_PMU_## name ##_SHIFT)
> +
> +#endif /* MFD_E31X_PMU_H */

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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