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Thu, 19 Mar 2026 09:17:43 -0700 (PDT) Date: Fri, 20 Mar 2026 00:17:37 +0800 From: Kuan-Wei Chiu To: Tomer Maimon Cc: andrew@codeconstruct.com.au, avifishman70@gmail.com, tali.perry1@gmail.com, srini@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, venture@google.com, yuenn@google.com, benjaminfair@google.com, jserv@ccns.ncku.edu.tw, eleanor15x@gmail.com, linux-arm-kernel@lists.infradead.org, openbmc@lists.ozlabs.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] nvmem: npcm-otp: Add Nuvoton NPCM OTP driver Message-ID: References: <20260318193538.246853-1-visitorckw@gmail.com> <20260318193538.246853-3-visitorckw@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Hi Tomer, On Thu, Mar 19, 2026 at 12:57:04PM +0200, Tomer Maimon wrote: > Hi Kuan-Wei, > > Thanks for the upstream Nuvoton OTP driver. > > On Wed, 18 Mar 2026 at 21:36, Kuan-Wei Chiu wrote: > > > > Add a new NVMEM driver for the OTP memory controllers found on Nuvoton > > NPCM SoCs. > > > > This OTP is read-only and manages two independent arrays: Key Storage > > and Fuse Array, which contain cryptographic keys, hardware strapping, > > and calibration data. > > > > Each array provides 1024 bytes of storage. > > > > It can be accessed by writing the target address and a read command > > to the control registers, and then polling a status register until > > the data is ready. Concurrent accesses are protected by a mutex. > > > > Signed-off-by: Kuan-Wei Chiu > > --- > > MAINTAINERS | 7 +++ > > drivers/nvmem/Kconfig | 10 +++ > > drivers/nvmem/Makefile | 2 + > > drivers/nvmem/npcm-otp.c | 129 +++++++++++++++++++++++++++++++++++++++ > > 4 files changed, 148 insertions(+) > > create mode 100644 drivers/nvmem/npcm-otp.c > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > index 61bf550fd37c..e391e2bcb5f6 100644 > > --- a/MAINTAINERS > > +++ b/MAINTAINERS > > @@ -18894,6 +18894,13 @@ F: drivers/nubus/ > > F: include/linux/nubus.h > > F: include/uapi/linux/nubus.h > > > > +NUVOTON NPCM OTP NVMEM DRIVER > > +M: Kuan-Wei Chiu > > +L: linux-arm-kernel@lists.infradead.org (moderated for non-subscribers) > > +S: Maintained > > +F: Documentation/devicetree/bindings/nvmem/nuvoton,npcm750-otp.yaml > > +F: drivers/nvmem/npcm-otp.c > > + > > NUVOTON NCT6694 MFD DRIVER > > M: Ming Yu > > S: Supported > > diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig > > index 74ddbd0f79b0..5d065b7448ff 100644 > > --- a/drivers/nvmem/Kconfig > > +++ b/drivers/nvmem/Kconfig > > @@ -483,4 +483,14 @@ config NVMEM_QORIQ_EFUSE > > This driver can also be built as a module. If so, the module > > will be called nvmem_qoriq_efuse. > > > > +config NVMEM_NPCM_OTP > > + tristate "Nuvoton NPCM7xx OTP Controller" > > + depends on ARCH_NPCM || COMPILE_TEST > > + help > > + This option enables support for the OTP (One-Time Programmable) > > + controller found on Nuvoton NPCM7xx BMCs. > > + > > + This driver can also be built as a module. If so, the module > > + will be called npcm-otp. > > + > > endif > > diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile > > index 7252b8ec88d4..63c23b304d64 100644 > > --- a/drivers/nvmem/Makefile > > +++ b/drivers/nvmem/Makefile > > @@ -95,3 +95,5 @@ obj-$(CONFIG_NVMEM_ZYNQMP) += nvmem_zynqmp_nvmem.o > > nvmem_zynqmp_nvmem-y := zynqmp_nvmem.o > > obj-$(CONFIG_NVMEM_QORIQ_EFUSE) += nvmem-qoriq-efuse.o > > nvmem-qoriq-efuse-y := qoriq-efuse.o > > +obj-$(CONFIG_NVMEM_NPCM_OTP) += nvmem-npcm-otp.o > > +nvmem-npcm-otp-y := npcm-otp.o > > diff --git a/drivers/nvmem/npcm-otp.c b/drivers/nvmem/npcm-otp.c > > new file mode 100644 > > index 000000000000..abe4bab66c06 > > --- /dev/null > > +++ b/drivers/nvmem/npcm-otp.c > > @@ -0,0 +1,129 @@ > > +// SPDX-License-Identifier: GPL-2.0-only > > +/* > > + * Nuvoton NPCM7xx OTP (One-Time Programmable) NVMEM driver > > + * > > + * Copyright (C) 2026 Kuan-Wei Chiu > > + */ > > + > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > + > > +/* Register offsets and bitmasks */ > > +#define NPCM_OTP_FST 0x00 > > +#define NPCM_OTP_FADDR 0x04 > > +#define NPCM_OTP_FDATA 0x08 > > +#define NPCM_OTP_FCTL 0x14 > > + > > +#define FST_RDY BIT(0) > > +#define FST_RDST BIT(1) > > +#define FCTL_READ_CMD 0x02 > > + > > +/* OTP total capacity is 8192 bits (1024 Bytes) */ > > +#define NPCM_OTP_SIZE 1024 > > + > > +struct npcm_otp { > > + void __iomem *base; > > + struct mutex lock; /* protects concurrent OTP accesses */ > > +}; > > + > > +static int npcm_otp_read_byte(struct npcm_otp *otp, unsigned int offset, u8 *val) > > +{ > > + u32 fst; > > + int ret; > > + > > + writel(offset, otp->base + NPCM_OTP_FADDR); > > + writel(FCTL_READ_CMD, otp->base + NPCM_OTP_FCTL); > > + > > + ret = readl_poll_timeout(otp->base + NPCM_OTP_FST, fst, > > + (fst & FST_RDY), 10, 10000); > > + if (ret) > > + return ret; > > + > > + *val = (u8)(readl(otp->base + NPCM_OTP_FDATA) & 0xFF); > > + > > + /* Clear the status bit to prepare for the next read */ > > + writel(FST_RDST, otp->base + NPCM_OTP_FST); > > + > > + return 0; > > +} > > + > > +static int npcm_otp_read(void *context, unsigned int offset, > > + void *val, size_t bytes) > > +{ > > + struct npcm_otp *otp = context; > > + u8 *buf = val; > > + int ret = 0; > > + size_t i; > > + > > + mutex_lock(&otp->lock); > > + > > + for (i = 0; i < bytes; i++) { > > + ret = npcm_otp_read_byte(otp, offset + i, &buf[i]); > > + if (ret) > > + break; > > + } > > + > > + mutex_unlock(&otp->lock); > > + > > + return ret; > > +} > > + > > +static int npcm_otp_probe(struct platform_device *pdev) > > +{ > > + struct device *dev = &pdev->dev; > > + struct npcm_otp *otp; > > + struct nvmem_config config = { 0 }; > > + struct nvmem_device *nvmem; > > + > > + otp = devm_kzalloc(dev, sizeof(*otp), GFP_KERNEL); > > + if (!otp) > > + return -ENOMEM; > > + > > + otp->base = devm_platform_ioremap_resource(pdev, 0); > > + if (IS_ERR(otp->base)) > > + return PTR_ERR(otp->base); > Since the driver already opens and manages the OTP registers, it > should also be responsible for handling the OTP index. > The NPCM AES driver can make use of keys stored in OTP. > We would be happy to help add support for OTP‑stored keys to the > upstream driver. > If you’d like, we can set up a meeting to discuss how this can be implemented. I would be very happy to collaborate. :) Regarding scheduling a meeting, I will be traveling abroad from 03/22 to 04/01 with very limited and unstable network access, so I would prefer to avoid that window. We can coordinate the exact date and time off-list. Regards, Kuan-Wei > > + > > + mutex_init(&otp->lock); > > + > > + config.dev = dev; > > + config.name = dev_name(dev); > > + config.read_only = true; > > + config.word_size = 1; > > + config.stride = 1; > > + config.reg_read = npcm_otp_read; > > + config.priv = otp; > > + config.size = NPCM_OTP_SIZE; > Suggest setting the size according to the BMC SoC, > The NPCM7xx has 2 8Kbyte OTP, and the NPCM8xx 64KB size.OPT > > + > > + nvmem = devm_nvmem_register(dev, &config); > > + if (IS_ERR(nvmem)) > > + return dev_err_probe(dev, PTR_ERR(nvmem), "Failed to register nvmem\n"); > > + > > + return 0; > > +} > > + > > +static const struct of_device_id npcm_otp_dt_ids[] = { > > + { .compatible = "nuvoton,npcm750-key-storage" }, > > + { .compatible = "nuvoton,npcm750-fuse-array" }, > > + { } > > +}; > > +MODULE_DEVICE_TABLE(of, npcm_otp_dt_ids); > > + > > +static struct platform_driver npcm_otp_driver = { > > + .probe = npcm_otp_probe, > > + .driver = { > > + .name = "npcm-otp", > > + .of_match_table = npcm_otp_dt_ids, > > + }, > > +}; > > +module_platform_driver(npcm_otp_driver); > > + > > +MODULE_AUTHOR("Kuan-Wei Chiu "); > > +MODULE_DESCRIPTION("Nuvoton NPCM7xx OTP NVMEM driver"); > > +MODULE_LICENSE("GPL"); > > -- > > 2.53.0.851.ga537e3e6e9-goog > > > > Thanks, > > Tomer