Re: [PATCH v2 02/11] mfd: renesas-vbattb: Add a MFD driver for the Renesas VBATTB IP

[claudiu beznea <claudiu.beznea@tuxon.dev>]

Hi, Biju,

On 16.07.2024 14:07, Biju Das wrote:
> Hi Claudiu,
> 
>> -----Original Message-----
>> From: Claudiu <claudiu.beznea@tuxon.dev>
>> Sent: Tuesday, July 16, 2024 11:30 AM
>> Subject: [PATCH v2 02/11] mfd: renesas-vbattb: Add a MFD driver for the Renesas VBATTB IP
>>
>> From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
>>
>> Renesas VBATTB IP has logic to control the RTC clock, tamper detection and a small 128B memory. Add a
>> MFD driver to do the basic initialization of the VBATTB IP for the inner components to work.
>>
>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
>> ---
>>
>> Changes in v2:
>> - none; this driver is new
>>
>>  drivers/mfd/Kconfig          |  8 ++++
>>  drivers/mfd/Makefile         |  1 +
>>  drivers/mfd/renesas-vbattb.c | 78 ++++++++++++++++++++++++++++++++++++
>>  3 files changed, 87 insertions(+)
>>  create mode 100644 drivers/mfd/renesas-vbattb.c
>>
>> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig index bc8be2e593b6..df93e8b05065 100644
>> --- a/drivers/mfd/Kconfig
>> +++ b/drivers/mfd/Kconfig
>> @@ -1383,6 +1383,14 @@ config MFD_SC27XX_PMIC
>>  	  This driver provides common support for accessing the SC27xx PMICs,
>>  	  and it also adds the irq_chip parts for handling the PMIC chip events.
>>
>> +config MFD_RENESAS_VBATTB
>> +	tristate "Renesas VBATTB driver"
>> +	depends on (ARCH_RZG2L && OF) || COMPILE_TEST
>> +	select MFD_CORE
>> +	help
>> +	  Select this option to enable Renesas RZ/G3S VBATTB driver which
>> +	  provides support for the RTC clock, tamper detector and 128B SRAM.
>> +
>>  config RZ_MTU3
>>  	tristate "Renesas RZ/G2L MTU3a core driver"
>>  	depends on (ARCH_RZG2L && OF) || COMPILE_TEST diff --git a/drivers/mfd/Makefile
>> b/drivers/mfd/Makefile index 02b651cd7535..cd2f27492df2 100644
>> --- a/drivers/mfd/Makefile
>> +++ b/drivers/mfd/Makefile
>> @@ -186,6 +186,7 @@ pcf50633-objs			:= pcf50633-core.o pcf50633-irq.o
>>  obj-$(CONFIG_MFD_PCF50633)	+= pcf50633.o
>>  obj-$(CONFIG_PCF50633_ADC)	+= pcf50633-adc.o
>>  obj-$(CONFIG_PCF50633_GPIO)	+= pcf50633-gpio.o
>> +obj-$(CONFIG_MFD_RENESAS_VBATTB)	+= renesas-vbattb.o
>>  obj-$(CONFIG_RZ_MTU3)		+= rz-mtu3.o
>>  obj-$(CONFIG_ABX500_CORE)	+= abx500-core.o
>>  obj-$(CONFIG_MFD_DB8500_PRCMU)	+= db8500-prcmu.o
>> diff --git a/drivers/mfd/renesas-vbattb.c b/drivers/mfd/renesas-vbattb.c new file mode 100644 index
>> 000000000000..5d71565b8cbf
>> --- /dev/null
>> +++ b/drivers/mfd/renesas-vbattb.c
>> @@ -0,0 +1,78 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * VBATTB driver
>> + *
>> + * Copyright (C) 2024 Renesas Electronics Corp.
>> + */
>> +
>> +#include <linux/mod_devicetable.h>
>> +#include <linux/of_platform.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/pm_runtime.h>
>> +#include <linux/reset.h>
>> +
>> +static int vbattb_probe(struct platform_device *pdev) {
>> +	struct device *dev = &pdev->dev;
>> +	struct reset_control *rstc;
>> +	int ret;
>> +
>> +	rstc = devm_reset_control_array_get_exclusive(dev);
>> +	if (IS_ERR(rstc))
>> +		return PTR_ERR(rstc);
>> +
>> +	ret = devm_pm_runtime_enable(dev);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = pm_runtime_resume_and_get(dev);
>> +	if (ret)
>> +		return ret;
> 
> Maybe as an optimization drop pm calls and use "devm_clk_get_enabled"
> instead as it perfectly fits in this scenario??

VBATTB is still part of a PM domain. That needs to be enabled as well.
pm_runtime_* APIs takes care of both clock enable and power domain on
operations.

One thing to notice is that on RZ/G3S the VBATTB clock is CRITICAL (thus
enabled in the probe of the clock driver), the PM domain is always ON (and
also enabled by clock driver). We can get rid of pm_runtime_* at all for
RZ/G3S but I think it would be better to have it here as well for future
platforms and to emphasize from driver that these resources are needed by
the VBATTB. The same approach is used for  other RZ/G2 drivers that
declares critical clocks/always-on domains (e.g. dma driver, IA55 driver).

Thank you,
Claudiu Beznea

> 
>> +
>> +	ret = reset_control_deassert(rstc);
>> +	if (ret)
>> +		goto rpm_put;
>> +
>> +	platform_set_drvdata(pdev, rstc);
>> +
>> +	ret = devm_of_platform_populate(dev);
>> +	if (ret)
>> +		goto reset_assert;
>> +
>> +	return 0;
>> +
>> +reset_assert:
>> +	reset_control_assert(rstc);
>> +rpm_put:
>> +	pm_runtime_put(dev);
>> +	return ret;
>> +}
>> +
>> +static void vbattb_remove(struct platform_device *pdev) {
>> +	struct reset_control *rstc = platform_get_drvdata(pdev);
>> +
>> +	reset_control_assert(rstc);
>> +	pm_runtime_put(&pdev->dev);
>> +}
>> +
>> +static const struct of_device_id vbattb_match[] = {
>> +	{ .compatible = "renesas,r9a08g045-vbattb" },
>> +	{ /* sentinel */ },
>> +};
>> +MODULE_DEVICE_TABLE(of, vbattb_match);
>> +
>> +static struct platform_driver vbattb_driver = {
>> +	.probe = vbattb_probe,
>> +	.remove_new = vbattb_remove,
>> +	.driver = {
>> +		.name = "renesas-vbattb",
>> +		.of_match_table = vbattb_match,
>> +	},
>> +};
>> +module_platform_driver(vbattb_driver);
>> +
>> +MODULE_ALIAS("platform:renesas-vbattb");
>> +MODULE_AUTHOR("Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>");
>> +MODULE_DESCRIPTION("Renesas VBATTB driver"); MODULE_LICENSE("GPL");
>> --
>> 2.39.2
>>
>