Re: [PATCH 3/4] nvmem: imx-ocotp: Support accessing controller for i.MX8M Nano

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

On Thu, Jan 30, 2025 at 02:01:00PM +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 | 105 +++++++++++++++++++++++++++++++++++++-
>  2 files changed, 107 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..e3ea026a37d0d 100644
> --- a/drivers/nvmem/imx-ocotp.c
> +++ b/drivers/nvmem/imx-ocotp.c
> @@ -23,6 +23,7 @@
>  #include <linux/of.h>
>  #include <linux/platform_device.h>
>  #include <linux/slab.h>
> +#include <dt-bindings/nvmem/fsl,imx8mn-ocotp.h>
>
>  #define IMX_OCOTP_OFFSET_B0W0		0x400 /* Offset from base address of the
>  					       * OTP Bank0 Word0
> @@ -91,11 +92,20 @@ struct ocotp_ctrl_reg {
>  	u32 bm_rel_shadows;
>  };
>
> +#define OCOTP_MAX_NUM_GATE_WORDS 4
> +
> +struct disable_fuse {
> +	u32 fuse_addr;
> +	u32 mask;
> +};
> +
>  struct ocotp_params {
>  	unsigned int nregs;
>  	unsigned int bank_address_words;
>  	void (*set_timing)(struct ocotp_priv *priv);
>  	struct ocotp_ctrl_reg ctrl;
> +	u32 num_disables;
> +	struct disable_fuse *disables;
>  };
>
>  static int imx_ocotp_wait_for_busy(struct ocotp_priv *priv, u32 flags)
> @@ -552,11 +562,25 @@ static const struct ocotp_params imx8mm_params = {
>  	.ctrl = IMX_OCOTP_BM_CTRL_DEFAULT,
>  };
>
> +struct disable_fuse imx8mn_disable_fuse[] = {
> +		[IMX8MN_OCOTP_M7_DISABLE]	= { .fuse_addr = 20, .mask = BIT(8) },
> +		[IMX8MN_OCOTP_M7_MPU_DISABLE]	= { .fuse_addr = 20, .mask = BIT(9) },
> +		[IMX8MN_OCOTP_M7_FPU_DISABLE]	= { .fuse_addr = 20, .mask = BIT(10) },
> +		[IMX8MN_OCOTP_USB_OTG1_DISABLE]	= { .fuse_addr = 20, .mask = BIT(11) },
> +		[IMX8MN_OCOTP_GPU3D_DISABLE]	= { .fuse_addr = 20, .mask = BIT(24) },
> +		[IMX8MN_OCOTP_MIPI_DSI_DISABLE]	= { .fuse_addr = 20, .mask = BIT(28) },
> +		[IMX8MN_OCOTP_ENET_DISABLE]	= { .fuse_addr = 20, .mask = BIT(29) },
> +		[IMX8MN_OCOTP_MIPI_CSI_DISABLE]	= { .fuse_addr = 20, .mask = BIT(30) },
> +		[IMX8MN_OCOTP_ASRC_DISABLE]	= { .fuse_addr = 20, .mask = BIT(31) },
> +};

Can we direct define IMX8MN_OCOTP_M7_DISABLE as BIT(8), so avoid this
map data?

> +
>  static const struct ocotp_params imx8mn_params = {
>  	.nregs = 256,
>  	.bank_address_words = 0,
>  	.set_timing = imx_ocotp_set_imx6_timing,
>  	.ctrl = IMX_OCOTP_BM_CTRL_DEFAULT,
> +	.num_disables = ARRAY_SIZE(imx8mn_disable_fuse),
> +	.disables = imx8mn_disable_fuse,
>  };
>
>  static const struct ocotp_params imx8mp_params = {
> @@ -589,6 +613,81 @@ 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 id)
> +{
> +	u32 addr, mask, ret, val;
> +
> +	if (id >= priv->params->num_disables) {
> +		dev_err(priv->dev, "Index %d too large\n", id);
> +		return -EACCES;
> +	}
> +
> +	addr = priv->params->disables[id].fuse_addr;
> +	mask = priv->params->disables[id].mask;
> +
> +	ret = imx_ocotp_read(priv, addr, &val, sizeof(val));
> +	if (ret)
> +		return ret;
> +
> +	dev_dbg(priv->dev, "id:%d addr:%#x mask:0x%08x\n", id, addr, mask);
> +	/* 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 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 disable ID: %d\n", child, id);
> +
> +			if (imx_ocotp_check_access(priv, id)) {
> +				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;
> +}

Can we have one method to share above code logic to avoid copy-paste to
every ocotp driver? Anyway, we can improve that later.

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


> +
> +static int imx_ocotp_access_control(struct ocotp_priv *priv)
> +{
> +	struct device_node *root __free(device_node) = of_find_node_by_path("/");
> +
> +	if (!priv->params->disables)
> +		return 0;
> +
> +	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 +721,13 @@ 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
>