Re: [PATCH v6 3/6] bus: add driver for IMX AIPSTZ bridge

[Shawn Guo <shawnguo2@yeah.net>]

On Tue, Apr 15, 2025 at 01:19:16PM -0400, Laurentiu Mihalcea wrote:
> From: Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>
> 
> The secure AHB to IP Slave (AIPSTZ) bus bridge provides access control
> configurations meant to restrict access to certain peripherals.
> Some of the configurations include:
> 
> 	1) Marking masters as trusted for R/W. Based on this
> 	(and the configuration of the accessed peripheral), the bridge
> 	may choose to abort the R/W transactions issued by certain
> 	masters.
> 
> 	2) Allowing/disallowing write accesses to peripherals.
> 
> Add driver for this IP. Since there's currently no framework for
> access controllers (and since there's currently no need for having
> flexibility w.r.t the configurations) all this driver does is it
> applies a relaxed, "default" configuration, in which all masters
> are trusted for R/W.
> 
> Note that some instances of this IP (e.g: AIPSTZ5 on i.MX8MP) may be tied
> to a power domain and may lose their configuration when the domain is
> powered off. This is why the configuration has to be restored when the
> domain is powered on.
> 
> Co-developed-by: Daniel Baluta <daniel.baluta@nxp.com>
> Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
> Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>
> ---
>  drivers/bus/Kconfig      |  6 +++
>  drivers/bus/Makefile     |  1 +
>  drivers/bus/imx-aipstz.c | 92 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 99 insertions(+)
>  create mode 100644 drivers/bus/imx-aipstz.c
> 
> diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
> index ff669a8ccad9..fe7600283e70 100644
> --- a/drivers/bus/Kconfig
> +++ b/drivers/bus/Kconfig
> @@ -87,6 +87,12 @@ config HISILICON_LPC
>  	  Driver to enable I/O access to devices attached to the Low Pin
>  	  Count bus on the HiSilicon Hip06/7 SoC.
>  
> +config IMX_AIPSTZ
> +	tristate "Support for IMX Secure AHB to IP Slave bus (AIPSTZ) bridge"
> +	depends on ARCH_MXC
> +	help
> +	  Enable support for IMX AIPSTZ bridge.
> +
>  config IMX_WEIM
>  	bool "Freescale EIM DRIVER"
>  	depends on ARCH_MXC || COMPILE_TEST
> diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
> index cddd4984d6af..8e693fe8a03a 100644
> --- a/drivers/bus/Makefile
> +++ b/drivers/bus/Makefile
> @@ -15,6 +15,7 @@ obj-$(CONFIG_FSL_MC_BUS)	+= fsl-mc/
>  
>  obj-$(CONFIG_BT1_APB)		+= bt1-apb.o
>  obj-$(CONFIG_BT1_AXI)		+= bt1-axi.o
> +obj-$(CONFIG_IMX_AIPSTZ)	+= imx-aipstz.o
>  obj-$(CONFIG_IMX_WEIM)		+= imx-weim.o
>  obj-$(CONFIG_INTEL_IXP4XX_EB)	+= intel-ixp4xx-eb.o
>  obj-$(CONFIG_MIPS_CDMM)		+= mips_cdmm.o
> diff --git a/drivers/bus/imx-aipstz.c b/drivers/bus/imx-aipstz.c
> new file mode 100644
> index 000000000000..44db40dae71b
> --- /dev/null
> +++ b/drivers/bus/imx-aipstz.c
> @@ -0,0 +1,92 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2025 NXP
> + */
> +
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/regmap.h>
> +
> +#define IMX_AIPSTZ_MPR0 0x0
> +
> +struct imx_aipstz_config {
> +	u32 mpr0;
> +};

Would it be more future-proof to have something like this?

struct imx_aipstz_priv {
	__iomem *base;
	const struct imx_aipstz_config *default_cfg;
}; 

With imx_aipstz_priv being drvdata, it could be easily scaled to have
more data later if needed. 

Shawn

> +
> +static void imx_aipstz_apply_default(void __iomem *base,
> +				     const struct imx_aipstz_config *default_cfg)
> +{
> +	writel(default_cfg->mpr0, base + IMX_AIPSTZ_MPR0);
> +}
> +
> +static int imx_aipstz_probe(struct platform_device *pdev)
> +{
> +	const struct imx_aipstz_config *default_cfg;
> +	void __iomem *base;
> +
> +	base = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
> +	if (IS_ERR(base))
> +		return dev_err_probe(&pdev->dev, -ENOMEM,
> +				     "failed to get/ioremap AC memory\n");
> +
> +	default_cfg = of_device_get_match_data(&pdev->dev);
> +
> +	imx_aipstz_apply_default(base, default_cfg);
> +
> +	dev_set_drvdata(&pdev->dev, base);
> +
> +	pm_runtime_set_active(&pdev->dev);
> +	devm_pm_runtime_enable(&pdev->dev);
> +
> +	return devm_of_platform_populate(&pdev->dev);
> +}
> +
> +static int imx_aipstz_runtime_resume(struct device *dev)
> +{
> +	const struct imx_aipstz_config *default_cfg;
> +	void __iomem *base;
> +
> +	base = dev_get_drvdata(dev);
> +	default_cfg = of_device_get_match_data(dev);
> +
> +	/* restore potentially lost configuration during domain power-off */
> +	imx_aipstz_apply_default(base, default_cfg);
> +
> +	return 0;
> +}
> +
> +static const struct dev_pm_ops imx_aipstz_pm_ops = {
> +	RUNTIME_PM_OPS(NULL, imx_aipstz_runtime_resume, NULL)
> +	SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
> +};
> +
> +/*
> + * following configuration is equivalent to:
> + *	masters 0-7 => trusted for R/W + use AHB's HPROT[1] to det. privilege
> + */
> +static const struct imx_aipstz_config imx8mp_aipstz_default_cfg = {
> +	.mpr0 = 0x77777777,
> +};
> +
> +static const struct of_device_id imx_aipstz_of_ids[] = {
> +	{ .compatible = "fsl,imx8mp-aipstz", .data = &imx8mp_aipstz_default_cfg },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, imx_aipstz_of_ids);
> +
> +static struct platform_driver imx_aipstz_of_driver = {
> +	.probe = imx_aipstz_probe,
> +	.driver = {
> +		.name = "imx-aipstz",
> +		.of_match_table = imx_aipstz_of_ids,
> +		.pm = pm_ptr(&imx_aipstz_pm_ops),
> +	},
> +};
> +module_platform_driver(imx_aipstz_of_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("IMX secure AHB to IP Slave bus (AIPSTZ) bridge driver");
> +MODULE_AUTHOR("Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>");
> -- 
> 2.34.1
>