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SubjectRe: [PATCH 2/4] nvmem: add generic driver for devices with MMIO access
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Hi,

On 2023/02/01 15:47, Rafał Miłecki wrote:
> From: Rafał Miłecki <rafal@milecki.pl>
>
> With nvmem layouts in place we should now work on plain content access
> NVMEM drivers (e.g. MMIO one). Actual NVMEM content handling should go
> to layout drivers.
>
> Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
> ---
> drivers/nvmem/Kconfig | 10 ++++++
> drivers/nvmem/Makefile | 2 ++
> drivers/nvmem/mmio.c | 80 ++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 92 insertions(+)
> create mode 100644 drivers/nvmem/mmio.c
>
> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
> index 789729ff7e50..9eb5e93f0455 100644
> --- a/drivers/nvmem/Kconfig
> +++ b/drivers/nvmem/Kconfig
> @@ -170,6 +170,16 @@ config NVMEM_MICROCHIP_OTPC
> This driver enable the OTP controller available on Microchip SAMA7G5
> SoCs. It controls the access to the OTP memory connected to it.
>
> +config NVMEM_MMIO
> + tristate "MMIO access based NVMEM support"
> + depends on HAS_IOMEM
> + help
> + This driver provides support for NVMEM devices that can be accessed
> + using MMIO.
> +
> + This driver can also be built as a module. If so, the module
> + will be called nvmem-mmio.
> +
> config NVMEM_MTK_EFUSE
> tristate "Mediatek SoCs EFUSE support"
> depends on ARCH_MEDIATEK || COMPILE_TEST
> diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
> index 442f9a4876a5..2f2bed7cdf24 100644
> --- a/drivers/nvmem/Makefile
> +++ b/drivers/nvmem/Makefile
> @@ -36,6 +36,8 @@ obj-$(CONFIG_NVMEM_MESON_MX_EFUSE) +=
> nvmem_meson_mx_efuse.o
> nvmem_meson_mx_efuse-y := meson-mx-efuse.o
> obj-$(CONFIG_NVMEM_MICROCHIP_OTPC) += nvmem-microchip-otpc.o
> nvmem-microchip-otpc-y := microchip-otpc.o
> +obj-$(CONFIG_NVMEM_MMIO) += nvmem-mmio.o
> +nvmem-mmio-y := mmio.o
> obj-$(CONFIG_NVMEM_MTK_EFUSE) += nvmem_mtk-efuse.o
> nvmem_mtk-efuse-y := mtk-efuse.o
> obj-$(CONFIG_NVMEM_MXS_OCOTP) += nvmem-mxs-ocotp.o
> diff --git a/drivers/nvmem/mmio.c b/drivers/nvmem/mmio.c
> new file mode 100644
> index 000000000000..19c8880dc675
> --- /dev/null
> +++ b/drivers/nvmem/mmio.c
> @@ -0,0 +1,80 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2023 Rafał Miłecki <rafal@milecki.pl>
> + */
> +
> +#include <linux/io.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/nvmem-provider.h>
> +#include <linux/platform_device.h>
> +#include <linux/property.h>
> +#include <linux/slab.h>
> +
> +struct mmio_nvmem {
> + void __iomem *base;
> +};
> +
> +static int mmio_nvmem_read(void *context, unsigned int offset, void *val,
> size_t bytes)
> +{
> + struct mmio_nvmem *priv = context;
> +
> + memcpy_fromio(val, priv->base, bytes);
> +
> + return 0;
> +}
> +
> +static int mmio_nvmem_probe(struct platform_device *pdev)
> +{
> + struct nvmem_config config = {
> + .name = "mmio-nvmem",

The fixed name breaks sysfs for multiple nvmem instances.

sysfs: cannot create duplicate filename '/bus/nvmem/devices/mmio-nvmem0'

> + .read_only = true,

As Michael said in the mediatek patch,
I also think it's hard to make read-only fixed in the generic driver.

> + .reg_read = mmio_nvmem_read,
> + };
> + struct device *dev = &pdev->dev;
> + struct mmio_nvmem *priv;
> + struct resource *res;
> +
> + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + priv->base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
> + if (IS_ERR(priv->base))
> + return PTR_ERR(priv->base);
> +
> + config.dev = dev;
> + config.size = resource_size(res);
> + config.word_size = sizeof(u8);
> + config.stride = sizeof(u8);
> + config.priv = priv;
> +
> + if (!device_property_present(dev, "read-only"))
> + dev_warn(dev, "Writing is not supported yet");

Isn't the logic opposite?
Anyway, the driver doesn't use "read-only" properties for selection.

> +
> + return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
> +}
> +
> +static const struct of_device_id mmio_nvmem_of_match_table[] = {
> + { .compatible = "mmio-nvmem", },
> + {},
> +};
> +
> +static struct platform_driver mmio_nvmem_driver = {
> + .probe = mmio_nvmem_probe,
> + .driver = {
> + .name = "mmio_nvmem",
> + .of_match_table = mmio_nvmem_of_match_table,
> + },
> +};
> +
> +static int __init mmio_nvmem_init(void)
> +{
> + return platform_driver_register(&mmio_nvmem_driver);
> +}
> +
> +subsys_initcall_sync(mmio_nvmem_init);
> +
> +MODULE_AUTHOR("Rafał Miłecki");
> +MODULE_LICENSE("GPL");
> +MODULE_DEVICE_TABLE(of, mmio_nvmem_of_match_table);

Thank you,

---
Best Regards
Kunihiko Hayashi

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