Re: [RFC PATCH 5/7] bus: stm32_sys_bus: add support for STM32MP15 and STM32MP13 system bus

[Krzysztof Kozlowski <krzk@kernel.org>]

On 21/12/2022 18:30, Gatien Chevallier wrote:
> This driver is checking the access rights of the different
> peripherals connected to the system bus. If access is denied,
> the associated device tree node is skipped so the platform bus
> does not probe it.
> 
> Signed-off-by: Loic PALLARDY <loic.pallardy@st.com>
> Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
> ---
>  MAINTAINERS                 |   6 ++
>  drivers/bus/Kconfig         |   9 ++
>  drivers/bus/Makefile        |   1 +
>  drivers/bus/stm32_sys_bus.c | 180 ++++++++++++++++++++++++++++++++++++
>  4 files changed, 196 insertions(+)
>  create mode 100644 drivers/bus/stm32_sys_bus.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 886d3f69ee64..768a8272233e 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -19522,6 +19522,12 @@ L:	linux-spi@vger.kernel.org
>  S:	Maintained
>  F:	drivers/spi/spi-stm32.c
>  
> +ST STM32 SYS BUS DRIVER
> +M:	Gatien Chevallier <gatien.chevallier@foss.st.com>
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/bus/st,sys-bus.yaml
> +F:	drivers/bus/stm32_sys_bus.c
> +
>  ST STPDDC60 DRIVER
>  M:	Daniel Nilsson <daniel.nilsson@flex.com>
>  L:	linux-hwmon@vger.kernel.org
> diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
> index 7bfe998f3514..638bf5839cb0 100644
> --- a/drivers/bus/Kconfig
> +++ b/drivers/bus/Kconfig
> @@ -163,6 +163,15 @@ config QCOM_SSC_BLOCK_BUS
>  	  i2c/spi/uart controllers, a hexagon core, and a clock controller
>  	  which provides clocks for the above.
>  
> +config STM32_SYS_BUS
> +	bool "STM32 System bus controller"
> +	depends on ARCH_STM32

|| COMPILE_TEST

> +	default MACH_STM32MP157 || MACH_STM32MP13
> +	help
> +	  Say y to enable device access right verification before device probing.
> +	  If access not granted, device won't be probed and an error message will
> +	  provide the reason.

(...)

> +
> +static int stm32_sys_bus_probe(struct platform_device *pdev)
> +{
> +	struct sys_bus_data *pdata;
> +	struct resource *res;
> +	void __iomem *mmio;
> +	struct stm32_sys_bus_match_data *mdata;
> +	struct device_node *np = pdev->dev.of_node;
> +
> +	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
> +	if (!pdata)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	mmio = devm_ioremap_resource(&pdev->dev, res);

Use helper for these two.

> +	if (IS_ERR(mmio))
> +		return PTR_ERR(mmio);
> +
> +	pdata->sys_bus_base = mmio;
> +
> +	mdata = (struct stm32_sys_bus_match_data *)of_device_get_match_data(&pdev->dev);

Why do you need the cast?

> +	if (!mdata)

Can you explain the case when this can actually happen? If it can, you
have bug in ID table.

> +		return -EINVAL;
> +
> +	pdata->pconf = mdata;
> +	pdata->dev = &pdev->dev;
> +
> +	platform_set_drvdata(pdev, pdata);
> +
> +	stm32_sys_bus_populate(pdata);
> +
> +	/* Populate all available nodes */
> +	return of_platform_populate(np, NULL, NULL, &pdev->dev);
> +}
> +
> +static const struct stm32_sys_bus_match_data stm32mp15_sys_bus_data = {
> +	.max_entries = STM32MP15_ETZPC_ENTRIES,
> +	.sys_bus_get_access = stm32_etzpc_get_access,
> +};
> +
> +static const struct stm32_sys_bus_match_data stm32mp13_sys_bus_data = {
> +	.max_entries = STM32MP13_ETZPC_ENTRIES,
> +	.sys_bus_get_access = stm32_etzpc_get_access,

It's the same as previous, drop.

> +};
> +
> +static const struct of_device_id stm32_sys_bus_of_match[] = {
> +	{ .compatible = "st,stm32mp15-sys-bus", .data = &stm32mp15_sys_bus_data },
> +	{ .compatible = "st,stm32mp13-sys-bus", .data = &stm32mp13_sys_bus_data },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, stm32_sys_bus_of_match);
> +
> +static struct platform_driver stm32_sys_bus_driver = {
> +	.probe  = stm32_sys_bus_probe,
> +	.driver = {
> +		.name = "stm32-sys-bus",
> +		.of_match_table = stm32_sys_bus_of_match,
> +	},
> +};
> +
> +static int __init stm32_sys_bus_init(void)
> +{
> +	return platform_driver_register(&stm32_sys_bus_driver);
> +}
> +arch_initcall(stm32_sys_bus_init);
> +

Best regards,
Krzysztof