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Message-ID: <Z5ur+NF9UlXJSWtL@lizhi-Precision-Tower-5810>
Date: Thu, 30 Jan 2025 11:42:32 -0500
From: Frank Li <Frank.li@....com>
To: Alexander Stein <alexander.stein@...tq-group.com>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
Sascha Hauer <s.hauer@...gutronix.de>,
Pengutronix Kernel Team <kernel@...gutronix.de>,
Fabio Estevam <festevam@...il.com>,
Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
devicetree@...r.kernel.org, imx@...ts.linux.dev,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] nvmem: imx-ocotp: Support accessing controller for
i.MX8M Nano
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@...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@....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
>
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