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([2a02:810d:15c0:828:7e24:6d1b:6bf:4249]) by smtp.gmail.com with ESMTPSA id y21-20020a1709060a9500b00965cd15c9bbsm1032892ejf.62.2023.05.18.07.22.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 18 May 2023 07:22:50 -0700 (PDT) Message-ID: Date: Thu, 18 May 2023 16:22:48 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH v2 2/3] nvmem: syscon: Add syscon backed nvmem driver Content-Language: en-US To: Marek Vasut , linux-arm-kernel@lists.infradead.org Cc: Alexandre Torgue , Conor Dooley , Krzysztof Kozlowski , Maxime Coquelin , Rob Herring , Srinivas Kandagatla , devicetree@vger.kernel.org, kernel@dh-electronics.com, linux-stm32@st-md-mailman.stormreply.com References: <20230517152513.27922-1-marex@denx.de> <20230517152513.27922-2-marex@denx.de> From: Krzysztof Kozlowski In-Reply-To: <20230517152513.27922-2-marex@denx.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 17/05/2023 17:25, Marek Vasut wrote: > Add trivial driver which permits exposing syscon backed register > to userspace. This is useful e.g. to expose U-Boot boot counter > on various platforms where the boot counter is stored in random > volatile register, like STM32MP15xx TAMP_BKPxR register. > > Signed-off-by: Marek Vasut > --- > Cc: Alexandre Torgue > Cc: Conor Dooley > Cc: Krzysztof Kozlowski > Cc: Marek Vasut > Cc: Maxime Coquelin > Cc: Rob Herring > Cc: Srinivas Kandagatla > Cc: devicetree@vger.kernel.org > Cc: kernel@dh-electronics.com > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-stm32@st-md-mailman.stormreply.com > --- > V2: No change > --- > drivers/nvmem/Kconfig | 10 ++++ > drivers/nvmem/Makefile | 2 + > drivers/nvmem/nvmem-syscon.c | 105 +++++++++++++++++++++++++++++++++++ > 3 files changed, 117 insertions(+) > create mode 100644 drivers/nvmem/nvmem-syscon.c > > diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig > index b291b27048c76..4e4aecdd9c293 100644 > --- a/drivers/nvmem/Kconfig > +++ b/drivers/nvmem/Kconfig > @@ -303,6 +303,16 @@ config NVMEM_STM32_BSEC_OPTEE_TA > This library is a used by stm32-romem driver or included in the module > called nvmem-stm32-romem. > > +config NVMEM_SYSCON > + tristate "Generic syscon backed nvmem" > + help > + This is a driver for generic syscon backed nvmem. This can be > + used to expose arbitrary syscon backed register to user space > + via nvmem, like the U-Boot boot counter. > + > + This driver can also be built as a module. If so, the module > + will be called nvmem-syscon. > + > config NVMEM_STM32_ROMEM > tristate "STMicroelectronics STM32 factory-programmed memory support" > depends on ARCH_STM32 || COMPILE_TEST > diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile > index f82431ec8aef0..d10e478e6a6c9 100644 > --- a/drivers/nvmem/Makefile > +++ b/drivers/nvmem/Makefile > @@ -60,6 +60,8 @@ obj-$(CONFIG_NVMEM_SPMI_SDAM) += nvmem_qcom-spmi-sdam.o > nvmem_qcom-spmi-sdam-y += qcom-spmi-sdam.o > obj-$(CONFIG_NVMEM_SPRD_EFUSE) += nvmem_sprd_efuse.o > nvmem_sprd_efuse-y := sprd-efuse.o > +obj-$(CONFIG_NVMEM_SYSCON) += nvmem_syscon.o > +nvmem_syscon-y := nvmem-syscon.o > obj-$(CONFIG_NVMEM_STM32_ROMEM) += nvmem_stm32_romem.o > nvmem_stm32_romem-y := stm32-romem.o > nvmem_stm32_romem-$(CONFIG_NVMEM_STM32_BSEC_OPTEE_TA) += stm32-bsec-optee-ta.o > diff --git a/drivers/nvmem/nvmem-syscon.c b/drivers/nvmem/nvmem-syscon.c > new file mode 100644 > index 0000000000000..e0aa5af0300d3 > --- /dev/null > +++ b/drivers/nvmem/nvmem-syscon.c > @@ -0,0 +1,105 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Copyright (C) 2022 Marek Vasut > + * > + * Based on snvs_lpgpr.c . > + */ > + > +#include > +#include > +#include > +#include > +#include > + > +struct nvmem_syscon_priv { > + struct device_d *dev; > + struct regmap *regmap; > + struct nvmem_config cfg; > + unsigned int off; > +}; > + > +static int nvmem_syscon_write(void *context, unsigned int offset, void *val, > + size_t bytes) > +{ > + struct nvmem_syscon_priv *priv = context; > + > + return regmap_bulk_write(priv->regmap, priv->off + offset, > + val, bytes / 4); > +} > + > +static int nvmem_syscon_read(void *context, unsigned int offset, void *val, > + size_t bytes) > +{ > + struct nvmem_syscon_priv *priv = context; > + > + return regmap_bulk_read(priv->regmap, priv->off + offset, > + val, bytes / 4); > +} > + > +static int nvmem_syscon_probe(struct platform_device *pdev) > +{ > + struct device *dev = &pdev->dev; > + struct device_node *node = dev->of_node; > + struct device_node *syscon_node; > + struct nvmem_syscon_priv *priv; > + struct nvmem_device *nvmem; > + struct nvmem_config *cfg; > + int ret; > + > + if (!node) > + return -ENOENT; > + > + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL); > + if (!priv) > + return -ENOMEM; > + > + ret = of_property_read_u32_index(node, "reg", 0, &priv->off); > + if (ret) > + return ret; > + > + ret = of_property_read_u32_index(node, "reg", 1, &priv->cfg.size); > + if (ret) > + return ret; > + > + syscon_node = of_get_parent(node); This does not look correct. You hard-code dependency that it must be a child of syscon node. This is weird requirement and not explained in the bindings. Why this cannot be then generic MMIO node? Why it has to be a child of syscon? > + if (!syscon_node) > + return -ENODEV; > + > + priv->regmap = syscon_node_to_regmap(syscon_node); > + of_node_put(syscon_node); > + if (IS_ERR(priv->regmap)) > + return PTR_ERR(priv->regmap); Best regards, Krzysztof