RE: [PATCH V4 2/4] rtc: add i.MX system controller RTC support

[Aisheng Dong <aisheng.dong@nxp.com>]

> -----Original Message-----
> From: Anson Huang
> Sent: Thursday, November 29, 2018 9:50 AM
[...]
> i.MX8QXP is an ARMv8 SoC which has a Cortex-M4 system controller inside,
> the system controller is in charge of controlling power, clock and secure rtc
> etc..
> 
> This patch adds i.MX system controller RTC driver support, Linux kernel has to
> communicate with system controller via MU (message unit) IPC to set/get RTC
> time and other alarm functions, since the RTC set time needs to be done in
> secure EL3 mode (required by system controller firmware) and alarm functions
> needs to be done with general MU IRQ handle, these depend on other
> components which are NOT ready, so this patch ONLY enables the RTC time
> read.
> 
> Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
> ---
> ChangeLog:
> V3->V4:
>   *remove unnecessary headfile included;
>   *fix potential memory currpution for the message responce;
>   *update the compatible string name to start with "fsl" instead of "nxp".
>  drivers/rtc/Kconfig      |  6 +++
>  drivers/rtc/Makefile     |  1 +
>  drivers/rtc/rtc-imx-sc.c | 98
> ++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 105 insertions(+)
>  create mode 100644 drivers/rtc/rtc-imx-sc.c
> 
> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig index a819ef0..3b9642e
> 100644
> --- a/drivers/rtc/Kconfig
> +++ b/drivers/rtc/Kconfig
> @@ -1677,6 +1677,12 @@ config RTC_DRV_SNVS
>  	   This driver can also be built as a module, if so, the module
>  	   will be called "rtc-snvs".
> 
> +config RTC_DRV_IMX_SC
> +	tristate "NXP i.MX System Controller RTC support"

This should depend on IMX_SCU

> +	help
> +	   If you say yes here you get support for the NXP i.MX System
> +	   Controller RTC module.
> +
>  config RTC_DRV_SIRFSOC
>  	tristate "SiRFSOC RTC"
>  	depends on ARCH_SIRF
> diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile index 290c173..f97c05e
> 100644
> --- a/drivers/rtc/Makefile
> +++ b/drivers/rtc/Makefile
> @@ -75,6 +75,7 @@ obj-$(CONFIG_RTC_DRV_GOLDFISH)	+= rtc-goldfish.o
>  obj-$(CONFIG_RTC_DRV_HID_SENSOR_TIME) += rtc-hid-sensor-time.o
>  obj-$(CONFIG_RTC_DRV_HYM8563)	+= rtc-hym8563.o
>  obj-$(CONFIG_RTC_DRV_IMXDI)	+= rtc-imxdi.o
> +obj-$(CONFIG_RTC_DRV_IMX_SC)	+= rtc-imx-sc.o
>  obj-$(CONFIG_RTC_DRV_ISL12022)	+= rtc-isl12022.o
>  obj-$(CONFIG_RTC_DRV_ISL12026)	+= rtc-isl12026.o
>  obj-$(CONFIG_RTC_DRV_ISL1208)	+= rtc-isl1208.o
> diff --git a/drivers/rtc/rtc-imx-sc.c b/drivers/rtc/rtc-imx-sc.c new file mode
> 100644 index 0000000..5976a2e
> --- /dev/null
> +++ b/drivers/rtc/rtc-imx-sc.c
> @@ -0,0 +1,98 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright 2018 NXP.
> + */
> +
> +#include <linux/firmware/imx/sci.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/rtc.h>
> +
> +#define IMX_SC_TIMER_FUNC_GET_RTC_SEC1970	9
> +#define IMX_SC_TIMER_FUNC_SET_RTC_TIME		6
> +
> +static struct imx_sc_ipc *rtc_ipc_handle; static struct rtc_device
> +*imx_sc_rtc;
> +
> +struct imx_sc_msg_timer_get_rtc_time {
> +	struct imx_sc_rpc_msg hdr;
> +	u32 time;
> +} __packed;
> +
> +static int imx_sc_rtc_read_time(struct device *dev, struct rtc_time
> +*tm) {
> +	struct imx_sc_msg_timer_get_rtc_time msg;
> +	struct imx_sc_rpc_msg *hdr = &msg.hdr;
> +	int ret;
> +
> +	hdr->ver = IMX_SC_RPC_VERSION;
> +	hdr->svc = IMX_SC_RPC_SVC_TIMER;
> +	hdr->func = IMX_SC_TIMER_FUNC_GET_RTC_SEC1970;
> +	hdr->size = 1;
> +
> +	ret = imx_scu_call_rpc(rtc_ipc_handle, &msg, true);
> +	if (ret) {
> +		pr_err("read rtc time failed, ret %d\n", ret);

Nitpick: 
better to use dev_err?

> +		return ret;
> +	}
> +
> +	rtc_time_to_tm(msg.time, tm);
> +
> +	return 0;
> +}
> +
> +static const struct rtc_class_ops imx_sc_rtc_ops = {
> +	.read_time = imx_sc_rtc_read_time,
> +};
> +
> +static int imx_sc_rtc_probe(struct platform_device *pdev) {
> +	int ret;
> +
> +	ret = imx_scu_get_handle(&rtc_ipc_handle);
> +	if (ret) {
> +		if (ret == -EPROBE_DEFER)
> +			return ret;
> +
> +		dev_err(&pdev->dev, "failed to get ipc handle: %d!\n", ret);
> +		return ret;
> +	}

You don't have to handle different error cases as API has already enclosed it.

> +
> +	imx_sc_rtc = devm_rtc_allocate_device(&pdev->dev);
> +	if (IS_ERR(imx_sc_rtc)) {
> +		ret = PTR_ERR(imx_sc_rtc);
> +		return ret;

Return PTR_ERR(imx_sc_rtc)

Regards
Dong Aisheng

> +	}
> +
> +	imx_sc_rtc->ops = &imx_sc_rtc_ops;
> +	imx_sc_rtc->range_min = 0;
> +	imx_sc_rtc->range_max = U32_MAX;
> +
> +	ret = rtc_register_device(imx_sc_rtc);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to register rtc: %d\n", ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id imx_sc_dt_ids[] = {
> +	{ .compatible = "fsl,imx8qxp-sc-rtc", },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, imx_sc_dt_ids);
> +
> +static struct platform_driver imx_sc_rtc_driver = {
> +	.driver = {
> +		.name	= "imx-sc-rtc",
> +		.of_match_table = imx_sc_dt_ids,
> +	},
> +	.probe		= imx_sc_rtc_probe,
> +};
> +module_platform_driver(imx_sc_rtc_driver);
> +
> +MODULE_AUTHOR("Anson Huang <Anson.Huang@nxp.com>");
> +MODULE_DESCRIPTION("NXP i.MX System Controller RTC Driver");
> +MODULE_LICENSE("GPL");
> --
> 2.7.4