Re: [PATCH v2 02/10] nvmem: imx-ocotp: Support accessing controller for i.MX8M

[Frank Li <Frank.li@nxp.com>]

On Fri, Feb 07, 2025 at 09:36:07AM +0100, Alexander Stein wrote:
> i.MX8M OCOTP supports a specific peripheral or function being fused
> which means disabled, so
>  - Introduce disable_fuse for a list of possible fused peripherals.
>  - Iterate all nodes to check accessing permission. If not
>    allowed to be accessed, detach the node
>
> Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
> ---
>  drivers/nvmem/Kconfig     |  3 ++
>  drivers/nvmem/imx-ocotp.c | 74 ++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 76 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
> index 8671b7c974b93..ba5c928cab520 100644
> --- a/drivers/nvmem/Kconfig
> +++ b/drivers/nvmem/Kconfig
> @@ -84,6 +84,9 @@ config NVMEM_IMX_OCOTP
>  	  This driver can also be built as a module. If so, the module
>  	  will be called nvmem-imx-ocotp.
>
> +	  If built as modules, any other driver relying on this working
> +	  as access controller also needs to be a module as well.
> +
>  config NVMEM_IMX_OCOTP_ELE
>  	tristate "i.MX On-Chip OTP Controller support"
>  	depends on ARCH_MXC || COMPILE_TEST
> diff --git a/drivers/nvmem/imx-ocotp.c b/drivers/nvmem/imx-ocotp.c
> index c5086a16450ac..b15cbdae66a7c 100644
> --- a/drivers/nvmem/imx-ocotp.c
> +++ b/drivers/nvmem/imx-ocotp.c
> @@ -589,6 +589,74 @@ static void imx_ocotp_fixup_dt_cell_info(struct nvmem_device *nvmem,
>  	cell->read_post_process = imx_ocotp_cell_pp;
>  }
>
> +static int imx_ocotp_check_access(struct ocotp_priv *priv, u32 addr, u32 bit)
> +{
> +	u32 mask, ret, val;
> +
> +	mask = BIT(bit);
> +
> +	ret = imx_ocotp_read(priv, addr, &val, sizeof(val));
> +	if (ret)
> +		return ret;
> +
> +	/* true means disabled */
> +	if (val & mask)
> +		return -EACCES;
> +
> +	return 0;
> +}
> +
> +static int imx_ocotp_grant_access(struct ocotp_priv *priv, struct device_node *parent)
> +{
> +	struct device *dev = priv->dev;
> +
> +	for_each_available_child_of_node_scoped(parent, child) {
> +		struct of_phandle_args args;
> +		u32 idx = 0;
> +		u32 addr;
> +		u32 bit;
> +
> +		while (!of_parse_phandle_with_args(child, "access-controllers",
> +						   "#access-controller-cells",
> +						   idx++, &args)) {
> +			of_node_put(args.np);
> +			if (args.np != dev->of_node)
> +				continue;
> +
> +			/* Only support one cell */

nit: two cell?

Reviewed-by: Frank Li <Frank.Li@nxp.com>

> +			if (args.args_count != 2) {
> +				dev_err(dev, "wrong args count\n");
> +				continue;
> +			}
> +
> +			addr = args.args[0];
> +			bit = args.args[1];
> +
> +			dev_dbg(dev, "Checking node: %pOF disable fuse addr: %u, bit %u\n", child, addr, bit);
> +
> +			if (imx_ocotp_check_access(priv, addr, bit)) {
> +				of_detach_node(child);
> +				dev_info(dev, "%pOF: disabled by fuse, device driver will not be probed\n",
> +					 child);
> +			}
> +		}
> +
> +		imx_ocotp_grant_access(priv, child);
> +	}
> +
> +	return 0;
> +}
> +
> +static int imx_ocotp_access_control(struct ocotp_priv *priv)
> +{
> +	struct device_node *root __free(device_node) = of_find_node_by_path("/");
> +
> +	if (WARN_ON(!root))
> +		return -EINVAL;
> +
> +	return imx_ocotp_grant_access(priv, root);
> +}
> +
>  static int imx_ocotp_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
> @@ -622,9 +690,13 @@ static int imx_ocotp_probe(struct platform_device *pdev)
>  	imx_ocotp_clr_err_if_set(priv);
>  	clk_disable_unprepare(priv->clk);
>
> +	platform_set_drvdata(pdev, priv);
> +
>  	nvmem = devm_nvmem_register(dev, &imx_ocotp_nvmem_config);
> +	if (IS_ERR(nvmem))
> +		return PTR_ERR(nvmem);
>
> -	return PTR_ERR_OR_ZERO(nvmem);
> +	return imx_ocotp_access_control(priv);
>  }
>
>  static struct platform_driver imx_ocotp_driver = {
> --
> 2.34.1
>