From: Oleksij Rempel Date: Thu, 21 Aug 2025 13:07:50 +0000 (+0200) Subject: mmc: core: Add infrastructure for undervoltage handling X-Git-Tag: v6.18-rc1~163^2~52 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3202d6ed9368fc1e842fda73727553ae614633f8;p=thirdparty%2Fkernel%2Fstable.git mmc: core: Add infrastructure for undervoltage handling Implement the core infrastructure to allow MMC bus types to handle REGULATOR_EVENT_UNDER_VOLTAGE events from power regulators. This is primarily aimed at allowing devices like eMMC to perform an emergency shutdown to prevent data corruption when a power failure is imminent. This patch introduces: - A new 'handle_undervoltage' function pointer to 'struct mmc_bus_ops'. Bus drivers (e.g., for eMMC) can implement this to define their emergency procedures. - A workqueue ('uv_work') in 'struct mmc_supply' to handle the event asynchronously in a high-priority context. - A new function 'mmc_handle_undervoltage()' which is called from the workqueue. It stops the host queue to prevent races with card removal, checks for the bus op, and invokes the handler. - Functions to register and unregister the regulator notifier, intended to be called by bus drivers like 'mmc_attach_mmc' when a compatible card is detected. The notifier is only registered for the main vmmc supply, as undervoltage handling for vqmmc or vqmmc2 is not required at this time. Signed-off-by: Oleksij Rempel Link: https://lore.kernel.org/r/20250821130751.2089587-2-o.rempel@pengutronix.de Signed-off-by: Ulf Hansson --- diff --git a/drivers/mmc/core/bus.c b/drivers/mmc/core/bus.c index 1cf64e0952fbe..ec4f3462bf809 100644 --- a/drivers/mmc/core/bus.c +++ b/drivers/mmc/core/bus.c @@ -19,6 +19,7 @@ #include #include +#include #include "core.h" #include "card.h" @@ -383,6 +384,14 @@ int mmc_add_card(struct mmc_card *card) mmc_card_set_present(card); + /* + * Register for undervoltage notification if the card supports + * power-off notification, enabling emergency shutdowns. + */ + if (mmc_card_mmc(card) && + card->ext_csd.power_off_notification == EXT_CSD_POWER_ON) + mmc_regulator_register_undervoltage_notifier(card->host); + return 0; } @@ -394,6 +403,9 @@ void mmc_remove_card(struct mmc_card *card) { struct mmc_host *host = card->host; + if (mmc_card_present(card)) + mmc_regulator_unregister_undervoltage_notifier(host); + mmc_remove_card_debugfs(card); if (mmc_card_present(card)) { diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c index 88fd231fee1d1..860378bea557b 100644 --- a/drivers/mmc/core/core.c +++ b/drivers/mmc/core/core.c @@ -1398,6 +1398,29 @@ void mmc_power_cycle(struct mmc_host *host, u32 ocr) mmc_power_up(host, ocr); } +/** + * mmc_handle_undervoltage - Handle an undervoltage event on the MMC bus + * @host: The MMC host that detected the undervoltage condition + * + * This function is called when an undervoltage event is detected on one of + * the MMC regulators. + * + * Returns: 0 on success or a negative error code on failure. + */ +int mmc_handle_undervoltage(struct mmc_host *host) +{ + /* Stop the host to prevent races with card removal */ + __mmc_stop_host(host); + + if (!host->bus_ops || !host->bus_ops->handle_undervoltage) + return 0; + + dev_warn(mmc_dev(host), "%s: Undervoltage detected, initiating emergency stop\n", + mmc_hostname(host)); + + return host->bus_ops->handle_undervoltage(host); +} + /* * Assign a mmc bus handler to a host. Only one bus handler may control a * host at any given time. diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h index 73f5d3d8c77d5..a028b48be1644 100644 --- a/drivers/mmc/core/core.h +++ b/drivers/mmc/core/core.h @@ -31,6 +31,7 @@ struct mmc_bus_ops { int (*sw_reset)(struct mmc_host *); bool (*cache_enabled)(struct mmc_host *); int (*flush_cache)(struct mmc_host *); + int (*handle_undervoltage)(struct mmc_host *host); }; void mmc_attach_bus(struct mmc_host *host, const struct mmc_bus_ops *ops); @@ -59,6 +60,10 @@ void mmc_power_off(struct mmc_host *host); void mmc_power_cycle(struct mmc_host *host, u32 ocr); void mmc_set_initial_state(struct mmc_host *host); u32 mmc_vddrange_to_ocrmask(int vdd_min, int vdd_max); +int mmc_handle_undervoltage(struct mmc_host *host); +void mmc_regulator_register_undervoltage_notifier(struct mmc_host *host); +void mmc_regulator_unregister_undervoltage_notifier(struct mmc_host *host); +void mmc_undervoltage_workfn(struct work_struct *work); static inline void mmc_delay(unsigned int ms) { diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c index f14671ea57162..5f0ec23aeff55 100644 --- a/drivers/mmc/core/host.c +++ b/drivers/mmc/core/host.c @@ -564,6 +564,8 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev) INIT_WORK(&host->sdio_irq_work, sdio_irq_work); timer_setup(&host->retune_timer, mmc_retune_timer, 0); + INIT_WORK(&host->supply.uv_work, mmc_undervoltage_workfn); + /* * By default, hosts do not support SGIO or large requests. * They have to set these according to their abilities. diff --git a/drivers/mmc/core/regulator.c b/drivers/mmc/core/regulator.c index 3dae2e9b79781..a85179f1a4de6 100644 --- a/drivers/mmc/core/regulator.c +++ b/drivers/mmc/core/regulator.c @@ -7,6 +7,7 @@ #include #include #include +#include #include @@ -262,6 +263,82 @@ static inline int mmc_regulator_get_ocrmask(struct regulator *supply) #endif /* CONFIG_REGULATOR */ +/* To be called from a high-priority workqueue */ +void mmc_undervoltage_workfn(struct work_struct *work) +{ + struct mmc_supply *supply; + struct mmc_host *host; + + supply = container_of(work, struct mmc_supply, uv_work); + host = container_of(supply, struct mmc_host, supply); + + mmc_handle_undervoltage(host); +} + +static int mmc_handle_regulator_event(struct notifier_block *nb, + unsigned long event, void *data) +{ + struct mmc_supply *supply = container_of(nb, struct mmc_supply, + vmmc_nb); + struct mmc_host *host = container_of(supply, struct mmc_host, supply); + unsigned long flags; + + switch (event) { + case REGULATOR_EVENT_UNDER_VOLTAGE: + spin_lock_irqsave(&host->lock, flags); + if (host->undervoltage) { + spin_unlock_irqrestore(&host->lock, flags); + return NOTIFY_OK; + } + + host->undervoltage = true; + spin_unlock_irqrestore(&host->lock, flags); + + queue_work(system_highpri_wq, &host->supply.uv_work); + break; + default: + return NOTIFY_DONE; + } + + return NOTIFY_OK; +} + +/** + * mmc_regulator_register_undervoltage_notifier - Register for undervoltage + * events + * @host: MMC host + * + * To be called by a bus driver when a card supporting graceful shutdown + * is attached. + */ +void mmc_regulator_register_undervoltage_notifier(struct mmc_host *host) +{ + int ret; + + if (IS_ERR_OR_NULL(host->supply.vmmc)) + return; + + host->supply.vmmc_nb.notifier_call = mmc_handle_regulator_event; + ret = regulator_register_notifier(host->supply.vmmc, + &host->supply.vmmc_nb); + if (ret) + dev_warn(mmc_dev(host), "Failed to register vmmc notifier: %d\n", ret); +} + +/** + * mmc_regulator_unregister_undervoltage_notifier - Unregister undervoltage + * notifier + * @host: MMC host + */ +void mmc_regulator_unregister_undervoltage_notifier(struct mmc_host *host) +{ + if (IS_ERR_OR_NULL(host->supply.vmmc)) + return; + + regulator_unregister_notifier(host->supply.vmmc, &host->supply.vmmc_nb); + cancel_work_sync(&host->supply.uv_work); +} + /** * mmc_regulator_get_supply - try to get VMMC and VQMMC regulators for a host * @mmc: the host to regulate diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h index 5ed5d203de23c..e0d935a4ac1d5 100644 --- a/include/linux/mmc/host.h +++ b/include/linux/mmc/host.h @@ -337,11 +337,15 @@ struct mmc_slot { struct regulator; struct mmc_pwrseq; +struct notifier_block; struct mmc_supply { struct regulator *vmmc; /* Card power supply */ struct regulator *vqmmc; /* Optional Vccq supply */ struct regulator *vqmmc2; /* Optional supply for phy */ + + struct notifier_block vmmc_nb; /* Notifier for vmmc */ + struct work_struct uv_work; /* Undervoltage work */ }; struct mmc_ctx { @@ -494,6 +498,13 @@ struct mmc_host { unsigned int can_dma_map_merge:1; /* merging can be used */ unsigned int vqmmc_enabled:1; /* vqmmc regulator is enabled */ + /* + * Indicates if an undervoltage event has already been handled. + * This prevents repeated regulator notifiers from triggering + * multiple REGULATOR_EVENT_UNDER_VOLTAGE events. + */ + unsigned int undervoltage:1; /* Undervoltage state */ + int rescan_disable; /* disable card detection */ int rescan_entered; /* used with nonremovable devices */