Re: [PATCH 5/5] firmware: imx: add i.MX95 MISC driver

[Cristian Marussi <cristian.marussi@arm.com>]

On Fri, Feb 02, 2024 at 02:34:43PM +0800, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@nxp.com>
> 
> The i.MX95 System manager exports SCMI MISC protocol for linux to do
> various settings, such as set board gpio expander as wakeup source.
> 

Hi,

> The driver is to add the support.
> 
> Signed-off-by: Peng Fan <peng.fan@nxp.com>
> ---
>  drivers/firmware/imx/Makefile   |  1 +
>  drivers/firmware/imx/sm-misc.c  | 92 +++++++++++++++++++++++++++++++++++++++++
>  include/linux/firmware/imx/sm.h | 33 +++++++++++++++
>  3 files changed, 126 insertions(+)
> 
> diff --git a/drivers/firmware/imx/Makefile b/drivers/firmware/imx/Makefile
> index fb20e22074e1..cb9c361d9b81 100644
> --- a/drivers/firmware/imx/Makefile
> +++ b/drivers/firmware/imx/Makefile
> @@ -2,3 +2,4 @@
>  obj-$(CONFIG_IMX_DSP)		+= imx-dsp.o
>  obj-$(CONFIG_IMX_SCU)		+= imx-scu.o misc.o imx-scu-irq.o rm.o imx-scu-soc.o
>  obj-${CONFIG_IMX_SCMI_BBM_EXT}	+= sm-bbm.o
> +obj-${CONFIG_IMX_SCMI_MISC_EXT}	+= sm-misc.o

Same considerations about missing Kconfig as in BBM and implicit
dependency on the NXP MISC vendor module...this way also you cannot even
NOT compile this module when the Vendor protocol is compiled in for,
say, testing purposes...

> diff --git a/drivers/firmware/imx/sm-misc.c b/drivers/firmware/imx/sm-misc.c
> new file mode 100644
> index 000000000000..4410e69d256b
> --- /dev/null
> +++ b/drivers/firmware/imx/sm-misc.c
> @@ -0,0 +1,92 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright 2024 NXP.
> + */
> +
> +#include <linux/firmware/imx/sm.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/scmi_protocol.h>
> +#include <linux/scmi_nxp_protocol.h>
> +
> +static const struct scmi_imx_misc_proto_ops *imx_misc_ctrl_ops;
> +static struct scmi_protocol_handle *ph;

This global does NOT sound right...if there are multiple SCMI instances
defined in the DT this can be probed multiple times, and the MISC
protocol will be initialized multuple times, each instance will have
its distinct protocol_handle *ph...so store it somewhere like you did in
the BBM driver

> +struct notifier_block scmi_imx_misc_ctrl_nb;
> +
> +int scmi_imx_misc_ctrl_set(u32 id, u32 val)
> +{
> +	if (!ph)
> +		return -EPROBE_DEFER;
> +
> +	return imx_misc_ctrl_ops->misc_ctrl_set(ph, id, 1, &val);
> +};
> +EXPORT_SYMBOL(scmi_imx_misc_ctrl_set);
> +
> +int scmi_imx_misc_ctrl_get(u32 id, u32 *num, u32 *val)
> +{
> +	if (!ph)
> +		return -EPROBE_DEFER;
> +
> +	return imx_misc_ctrl_ops->misc_ctrl_get(ph, id, num, val);
> +}
> +EXPORT_SYMBOL(scmi_imx_misc_ctrl_get);
> +

Ok, now I suppose that you want to be sure to run just one instance if
this driver...

> +static int scmi_imx_misc_ctrl_notifier(struct notifier_block *nb,
> +				       unsigned long event, void *data)
> +{
> +	return 0;
> +}

What is the point of this ?

> +
> +static int scmi_imx_misc_ctrl_probe(struct scmi_device *sdev)
> +{
> +	const struct scmi_handle *handle = sdev->handle;
> +	struct device_node *np = sdev->dev.of_node;
> +	u32 src_id, evt_id, wu_num;
> +	int ret, i;
> +
> +	if (!handle)
> +		return -ENODEV;
> +
> +	imx_misc_ctrl_ops = handle->devm_protocol_get(sdev, SCMI_PROTOCOL_IMX_MISC, &ph);
> +	if (IS_ERR(imx_misc_ctrl_ops))
> +		return PTR_ERR(imx_misc_ctrl_ops);
> +
> +	scmi_imx_misc_ctrl_nb.notifier_call = &scmi_imx_misc_ctrl_notifier;
> +	wu_num = of_property_count_u32_elems(np, "wakeup-sources");
> +	if (wu_num % 2) {
> +		dev_err(&sdev->dev, "Invalid wakeup-sources\n");
> +		return -EINVAL;
> +	}
> +
> +	for (i = 0; i < wu_num; i += 2) {
> +		WARN_ON(of_property_read_u32_index(np, "wakeup-sources", i, &src_id));
> +		WARN_ON(of_property_read_u32_index(np, "wakeup-sources", i + 1, &evt_id));
> +		ret = handle->notify_ops->devm_event_notifier_register(sdev, SCMI_PROTOCOL_IMX_MISC,
> +								       evt_id,
> +								       &src_id,
> +								       &scmi_imx_misc_ctrl_nb);

...when probed more than once this will lead to the same global nb registered on 2
different notification chains....

> +		if (ret)
> +			dev_err(&sdev->dev, "Failed to register scmi misc event: %d\n", src_id);
> +	}
> +
> +	return 0;
> +
> +}
> +
> +static const struct scmi_device_id scmi_id_table[] = {
> +	{ SCMI_PROTOCOL_IMX_MISC, "imx-misc-ctrl" },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(scmi, scmi_id_table);
> +
> +static struct scmi_driver scmi_imx_misc_ctrl_driver = {
> +	.name = "scmi-imx-misc-ctrl",
> +	.probe = scmi_imx_misc_ctrl_probe,
> +	.id_table = scmi_id_table,
> +};
> +module_scmi_driver(scmi_imx_misc_ctrl_driver);
> +

All in all, I suppose the main thing to reason about this driver is if you
want/plan to allow for multiple instances of it to be loaded/probed on the same
running system or not...

If you think that this driver HAS STRICTLY to be probed once, and having
2 DT protocol nodes for MISC it is certainly an error, we will have to
add some mechianism in the SCMI core to be able to mark this as single
instance and refuse to create more than one device for this protocol...a
sort of generalization of what is done in a custom way by the core for
SYSTEM_POWER, since we dont want to have multiple sources of shutdown
events...

Alternnatively you will have to make this survive multiple
probes...keeping track of multiple *ph for each probe() and handling
that in your EXPORTED funcs...thing that seems awkard a bit...but you
only know how this is an will be used.

> +MODULE_AUTHOR("Peng Fan <peng.fan@nxp.com>");
> +MODULE_DESCRIPTION("IMX SM MISC driver");
> +MODULE_LICENSE("GPL");
> diff --git a/include/linux/firmware/imx/sm.h b/include/linux/firmware/imx/sm.h
> new file mode 100644
> index 000000000000..daad4bdf7d1c
> --- /dev/null
> +++ b/include/linux/firmware/imx/sm.h
> @@ -0,0 +1,33 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +/*
> + * Copyright 2024 NXP
> + */
> +
> +#ifndef _SCMI_IMX_H
> +#define _SCMI_IMX_H
> +
> +#include <linux/bitfield.h>
> +#include <linux/types.h>
> +
> +#define SCMI_IMX_CTRL_PDM_CLK_SEL	0	/* AON PDM clock sel */
> +#define SCMI_IMX_CTRL_MQS1_SETTINGS	1	/* AON MQS settings */
> +#define SCMI_IMX_CTRL_SAI1_MCLK		2	/* AON SAI1 MCLK */
> +#define SCMI_IMX_CTRL_SAI3_MCLK		3	/* WAKE SAI3 MCLK */
> +#define SCMI_IMX_CTRL_SAI4_MCLK		4	/* WAKE SAI4 MCLK */
> +#define SCMI_IMX_CTRL_SAI5_MCLK		5	/* WAKE SAI5 MCLK */
> +
> +#if IS_ENABLED(CONFIG_IMX_SCMI_MISC_EXT)
> +int scmi_imx_misc_ctrl_get(u32 id, u32 *num, u32 *val);
> +int scmi_imx_misc_ctrl_set(u32 id, u32 val);
> +#else
> +static inline int scmi_imx_misc_ctrl_get(u32 id, u32 *num, u32 *val)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static inline int scmi_imx_misc_ctrl_set(u32 id, u32 val);
> +{
> +	return -EOPNOTSUPP;
> +}
> +#endif
> +#endif
> 

Thanks,
Cristian

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