Re: [PATCH v6 2/2] nvmem: imx-ocotp-ele: Support accessing controller for i.MX9

[Alexander Stein <alexander.stein@ew.tq-group.com>]

Hi,

Am Dienstag, 21. Januar 2025, 16:05:32 CET schrieb Peng Fan (OSS):
> From: Peng Fan <peng.fan@nxp.com>
> 
> i.MX9 OCOTP supports a specific peripheral or function being fused
> which means disabled, so
>  - Introduce ocotp_access_gates to be container of efuse gate info
>  - Iterate all nodes to check accessing permission. If not
>    allowed to be accessed, detach the node
> 
> Signed-off-by: Peng Fan <peng.fan@nxp.com>
> ---
>  drivers/nvmem/Kconfig         |   3 +
>  drivers/nvmem/imx-ocotp-ele.c | 172 +++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 174 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
> index 8671b7c974b933e147154bb40b5d41b5730518d2..77cc496fd5e0e1afd753534b56fe1f5ef3e3ec55 100644
> --- a/drivers/nvmem/Kconfig
> +++ b/drivers/nvmem/Kconfig
> @@ -93,6 +93,9 @@ config NVMEM_IMX_OCOTP_ELE
>  	  This is a driver for the On-Chip OTP Controller (OCOTP)
>  	  available on i.MX SoCs which has ELE.
>  
> +	  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_SCU
>  	tristate "i.MX8 SCU On-Chip OTP Controller support"
>  	depends on IMX_SCU
> diff --git a/drivers/nvmem/imx-ocotp-ele.c b/drivers/nvmem/imx-ocotp-ele.c
> index ca6dd71d8a2e29888c6e556aaea116c1a967cb5f..5ea6d959ce38760eeed44a989992fb35c462c0b4 100644
> --- a/drivers/nvmem/imx-ocotp-ele.c
> +++ b/drivers/nvmem/imx-ocotp-ele.c
> @@ -5,6 +5,8 @@
>   * Copyright 2023 NXP
>   */
>  
> +#include <dt-bindings/nvmem/fsl,imx93-ocotp.h>
> +#include <dt-bindings/nvmem/fsl,imx95-ocotp.h>
>  #include <linux/device.h>
>  #include <linux/io.h>
>  #include <linux/module.h>
> @@ -27,6 +29,7 @@ struct ocotp_map_entry {
>  };
>  
>  struct ocotp_devtype_data {
> +	const struct ocotp_access_gates *access_gates;
>  	u32 reg_off;
>  	char *name;
>  	u32 size;
> @@ -36,6 +39,20 @@ struct ocotp_devtype_data {
>  	struct ocotp_map_entry entry[];
>  };
>  
> +#define OCOTP_MAX_NUM_GATE_WORDS 4
> +
> +struct access_gate {
> +	u32 word;
> +	u32 mask;
> +};
> +
> +struct ocotp_access_gates {
> +	u32 num_words;
> +	u32 words[OCOTP_MAX_NUM_GATE_WORDS];
> +	u32 num_gates;
> +	struct access_gate *gates;
> +};
> +
>  struct imx_ocotp_priv {
>  	struct device *dev;
>  	void __iomem *base;
> @@ -131,6 +148,82 @@ static void imx_ocotp_fixup_dt_cell_info(struct nvmem_device *nvmem,
>  	cell->read_post_process = imx_ocotp_cell_pp;
>  }
>  
> +static int imx_ele_ocotp_check_access(struct imx_ocotp_priv *priv, u32 id)
> +{
> +	const struct ocotp_access_gates *access_gates = priv->data->access_gates;
> +	void __iomem *reg = priv->base + priv->data->reg_off;
> +	u32 word, mask, val;
> +
> +	if (id >= access_gates->num_gates) {
> +		dev_err(priv->config.dev, "Index %d too large\n", id);
> +		return -EACCES;
> +	}
> +
> +	word = access_gates->gates[id].word;
> +	mask = access_gates->gates[id].mask;
> +
> +	reg = priv->base + priv->data->reg_off + (word << 2);
> +	val = readl(reg);
> +
> +	dev_dbg(priv->config.dev, "id:%d word:%d mask:0x%08x\n", id, word, mask);
> +	/* true means not allow access */
> +	if (val & mask)
> +		return -EACCES;
> +
> +	return 0;
> +}
> +
> +static int imx_ele_ocotp_grant_access(struct imx_ocotp_priv *priv, struct device_node *parent)
> +{
> +	struct device *dev = priv->config.dev;
> +
> +	for_each_available_child_of_node_scoped(parent, child) {
> +		struct of_phandle_args args;
> +		u32 id, idx = 0;
> +
> +		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 */
> +			if (args.args_count != 1) {
> +				dev_err(dev, "wrong args count\n");
> +				continue;
> +			}
> +
> +			id = args.args[0];
> +
> +			dev_dbg(dev, "Checking node: %pOF gate: %d\n", child, id);
> +
> +			if (imx_ele_ocotp_check_access(priv, id)) {
> +				of_detach_node(child);
> +				dev_info(dev, "%pOF: Not granted, device driver will not be probed\n",
> +					 child);
> +			}
> +		}
> +
> +		imx_ele_ocotp_grant_access(priv, child);
> +	}
> +
> +	return 0;
> +}
> +
> +static int imx_ele_ocotp_access_control(struct imx_ocotp_priv *priv)
> +{
> +	struct device_node *root __free(device_node) = of_find_node_by_path("/");
> +
> +	if (!priv->data->access_gates)
> +		return 0;
> +
> +	/* This should never happen */
> +	WARN_ON(!root);

Even if you warning something is wrong, aka root == NULL, you are still
using it on imx_ele_ocotp_grant_access(). Just return early.

if (WARN_ON(!))
	return -EINVAL;

Best regards
Alexander

> +
> +	return imx_ele_ocotp_grant_access(priv, root);
> +}
> +
>  static int imx_ele_ocotp_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
> @@ -161,14 +254,45 @@ static int imx_ele_ocotp_probe(struct platform_device *pdev)
>  	priv->config.fixup_dt_cell_info = imx_ocotp_fixup_dt_cell_info;
>  	mutex_init(&priv->lock);
>  
> +	platform_set_drvdata(pdev, priv);
> +
>  	nvmem = devm_nvmem_register(dev, &priv->config);
>  	if (IS_ERR(nvmem))
>  		return PTR_ERR(nvmem);
>  
> -	return 0;
> +
> +	return imx_ele_ocotp_access_control(priv);
>  }



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