From b9936aa8a3775c2027f655d91a206d0e6e1c7ec0 Mon Sep 17 00:00:00 2001 From: Daniel Golle Date: Tue, 11 Jul 2023 00:17:31 +0100 Subject: [PATCH 11/15] block: implement NVMEM provider On embedded devices using an eMMC it is common that one or more partitions on the eMMC are used to store MAC addresses and Wi-Fi calibration EEPROM data. Allow referencing the partition in device tree for the kernel and Wi-Fi drivers accessing it via the NVMEM layer. Signed-off-by: Daniel Golle --- block/Kconfig | 9 +++ block/Makefile | 1 + block/blk-nvmem.c | 186 ++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 196 insertions(+) create mode 100644 block/blk-nvmem.c --- a/block/Kconfig +++ b/block/Kconfig @@ -203,6 +203,15 @@ config BLK_INLINE_ENCRYPTION_FALLBACK by falling back to the kernel crypto API when inline encryption hardware is not present. +config BLK_NVMEM + bool "Block device NVMEM provider" + depends on OF + depends on NVMEM + help + Allow block devices (or partitions) to act as NVMEM prodivers, + typically used with eMMC to store MAC addresses or Wi-Fi + calibration data on embedded devices. + source "block/partitions/Kconfig" config BLOCK_COMPAT --- a/block/Makefile +++ b/block/Makefile @@ -35,6 +35,7 @@ obj-$(CONFIG_BLK_DEV_ZONED) += blk-zoned obj-$(CONFIG_BLK_WBT) += blk-wbt.o obj-$(CONFIG_BLK_DEBUG_FS) += blk-mq-debugfs.o obj-$(CONFIG_BLK_DEBUG_FS_ZONED)+= blk-mq-debugfs-zoned.o +obj-$(CONFIG_BLK_NVMEM) += blk-nvmem.o obj-$(CONFIG_BLK_SED_OPAL) += sed-opal.o obj-$(CONFIG_BLK_PM) += blk-pm.o obj-$(CONFIG_BLK_INLINE_ENCRYPTION) += blk-crypto.o blk-crypto-profile.o \ --- /dev/null +++ b/block/blk-nvmem.c @@ -0,0 +1,186 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * block device NVMEM provider + * + * Copyright (c) 2023 Daniel Golle + * + * Useful on devices using a partition on an eMMC for MAC addresses or + * Wi-Fi calibration EEPROM data. + */ + +#include "blk.h" +#include +#include +#include +#include + +/* List of all NVMEM devices */ +static LIST_HEAD(nvmem_devices); +static DEFINE_MUTEX(devices_mutex); + +struct blk_nvmem { + struct nvmem_device *nvmem; + struct block_device *bdev; + struct list_head list; +}; + +static int blk_nvmem_reg_read(void *priv, unsigned int from, + void *val, size_t bytes) +{ + unsigned long offs = from & ~PAGE_MASK, to_read; + pgoff_t f_index = from >> PAGE_SHIFT; + struct address_space *mapping; + struct blk_nvmem *bnv = priv; + size_t bytes_left = bytes; + struct folio *folio; + void *p; + int ret; + + if (!bnv->bdev) + return -ENODEV; + + if (!bnv->bdev->bd_disk) + return -EINVAL; + + if (!bnv->bdev->bd_disk->fops) + return -EIO; + + if (!bnv->bdev->bd_disk->fops->open) + return -EIO; + + ret = bnv->bdev->bd_disk->fops->open(bnv->bdev, FMODE_READ); + if (ret) + return ret; + + mapping = bnv->bdev->bd_inode->i_mapping; + + while (bytes_left) { + folio = read_mapping_folio(mapping, f_index++, NULL); + if (IS_ERR(folio)) { + ret = PTR_ERR(folio); + goto err_release_bdev; + } + to_read = min_t(unsigned long, bytes_left, PAGE_SIZE - offs); + p = folio_address(folio) + offset_in_folio(folio, offs); + memcpy(val, p, to_read); + offs = 0; + bytes_left -= to_read; + val += to_read; + folio_put(folio); + } + +err_release_bdev: + bnv->bdev->bd_disk->fops->release(bnv->bdev->bd_disk, FMODE_READ); + + return ret; +} + +static int blk_nvmem_register(struct device *dev, struct class_interface *iface) +{ + struct device_node *np = dev_of_node(dev); + struct block_device *bdev = dev_to_bdev(dev); + struct nvmem_config config = {}; + struct blk_nvmem *bnv; + + /* skip devices which do not have a device tree node */ + if (!np) + return 0; + + /* skip devices without an nvmem layout defined */ + if (!of_get_child_by_name(np, "nvmem-layout")) + return 0; + + /* + * skip devices which don't have GENHD_FL_NVMEM set + * + * This flag is used for mtdblock and ubiblock devices because + * both, MTD and UBI already implement their own NVMEM provider. + * To avoid registering multiple NVMEM providers for the same + * device node, don't register the block NVMEM provider for them. + */ + if (!(bdev->bd_disk->flags & GENHD_FL_NVMEM)) + return 0; + + /* + * skip block device too large to be represented as NVMEM devices + * which are using an 'int' as address + */ + if (bdev_nr_bytes(bdev) > INT_MAX) + return -EFBIG; + + bnv = kzalloc(sizeof(struct blk_nvmem), GFP_KERNEL); + if (!bnv) + return -ENOMEM; + + config.id = NVMEM_DEVID_NONE; + config.dev = &bdev->bd_device; + config.name = dev_name(&bdev->bd_device); + config.owner = THIS_MODULE; + config.priv = bnv; + config.reg_read = blk_nvmem_reg_read; + config.size = bdev_nr_bytes(bdev); + config.word_size = 1; + config.stride = 1; + config.read_only = true; + config.root_only = true; + config.ignore_wp = true; + config.of_node = to_of_node(dev->fwnode); + + bnv->bdev = bdev; + bnv->nvmem = nvmem_register(&config); + if (IS_ERR(bnv->nvmem)) { + dev_err_probe(&bdev->bd_device, PTR_ERR(bnv->nvmem), + "Failed to register NVMEM device\n"); + + kfree(bnv); + return PTR_ERR(bnv->nvmem); + } + + mutex_lock(&devices_mutex); + list_add_tail(&bnv->list, &nvmem_devices); + mutex_unlock(&devices_mutex); + + return 0; +} + +static void blk_nvmem_unregister(struct device *dev, struct class_interface *iface) +{ + struct block_device *bdev = dev_to_bdev(dev); + struct blk_nvmem *bnv_c, *bnv = NULL; + + mutex_lock(&devices_mutex); + list_for_each_entry(bnv_c, &nvmem_devices, list) { + if (bnv_c->bdev == bdev) { + bnv = bnv_c; + break; + } + } + + if (!bnv) { + mutex_unlock(&devices_mutex); + return; + } + + list_del(&bnv->list); + mutex_unlock(&devices_mutex); + nvmem_unregister(bnv->nvmem); + kfree(bnv); +} + +static struct class_interface blk_nvmem_bus_interface __refdata = { + .class = &block_class, + .add_dev = &blk_nvmem_register, + .remove_dev = &blk_nvmem_unregister, +}; + +static int __init blk_nvmem_init(void) +{ + int ret; + + ret = class_interface_register(&blk_nvmem_bus_interface); + if (ret) + return ret; + + return 0; +} +device_initcall(blk_nvmem_init);