STRUCT ATMEL_MCI(9)

💖 struct atmel_mci 💖

okay bestie, welcome to the Kernel API Manual, section 9 — this page is literally all about struct atmel_mci, and we're gonna get into every single field without skipping a crumb 🍓

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🌸 NAME 🌸

struct atmel_mci — MMC controller state shared between all slots. periodt 💅

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✨ SYNOPSIS ✨

struct atmel_mci {
    spinlock_t lock;
    void __iomem            *regs;
    struct scatterlist      *sg;
    unsigned int            sg_len;
    unsigned int            pio_offset;
    unsigned int            *buffer;
    unsigned int            buf_size;
    dma_addr_t buf_phys_addr;
    struct atmel_mci_slot   *cur_slot;
    struct mmc_request      *mrq;
    struct mmc_command      *cmd;
    struct mmc_data         *data;
    unsigned int            data_size;
    struct atmel_mci_dma    dma;
    struct dma_chan         *data_chan;
    struct dma_slave_config dma_conf;
    u32 cmd_status;
    u32 data_status;
    u32 stop_cmdr;
    struct work_struct      bh_work;
    unsigned long           pending_events;
    unsigned long           completed_events;
    enum atmel_mci_state    state;
    struct list_head        queue;
    bool need_clock_update;
    bool need_reset;
    struct timer_list       timer;
    u32 mode_reg;
    u32 cfg_reg;
    unsigned long           bus_hz;
    unsigned long           mapbase;
    struct clk              *mck;
    struct device           *dev;
    struct mci_slot_pdata   pdata[ATMCI_MAX_NR_SLOTS];
    struct atmel_mci_slot   *slot[ATMCI_MAX_NR_SLOTS];
    struct atmel_mci_caps   caps;
    u32 (*prepare_data)(struct atmel_mci *host, struct mmc_data *data);
    void (*submit_data)(struct atmel_mci *host, struct mmc_data *data);
    void (*stop_transfer)(struct atmel_mci *host);
 };

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🫶 Members 🫶

• lock — spinlock protecting the queue and associated data, no cap.
• regs — pointer to MMIO registers ✨
• sg — scatterlist entry currently being processed by PIO or PDC code.
• sg_len — size of the scatterlist.
• pio_offset — offset into the current scatterlist entry.
• buffer — buffer used if we don't have the r/w proof capability. We don't have the time to switch pdc buffers so we have to use only one buffer for the full transaction. it's giving efficiency 💀
• buf_size — size of the buffer.
• buf_phys_addr — buffer address needed for pdc.
• cur_slot — the slot which is currently using the controller 👑
• mrq — the request currently being processed on cur_slot, or NULL if the controller is idle.
• cmd — the command currently being sent to the card, or NULL.
• data — the data currently being transferred, or NULL if no data transfer is in progress.
• data_size — just data->blocks * data->blksz.
• dma — DMA client state.
• data_chan — DMA channel being used for the current data transfer.
• dma_conf — configuration for the DMA slave.
• cmd_status — snapshot of SR taken upon completion of the current command. Only valid when EVENT_CMD_COMPLETE is pending. iykyk 🔥
• data_status — snapshot of SR taken upon completion of the current data transfer. Only valid when EVENT_DATA_COMPLETE or EVENT_DATA_ERROR is pending.
• stop_cmdr — value to be loaded into CMDR when the stop command is to be sent.
• bh_work — work running the request state machine.
• pending_events — bitmask of events flagged by the interrupt handler to be processed by the work.
• completed_events — bitmask of events which the state machine has processed.
• state — work state.
• queue — list of slots waiting for access to the controller.
• need_clock_update — update the clock rate before the next request.
• need_reset — reset controller before next request.
• timer — timer to balance the data timeout error flag which cannot rise.
• mode_reg — value of the MR register.
• cfg_reg — value of the CFG register.
• bus_hz — the rate of mck in Hz. This forms the basis for MMC bus rate and timeout calculations.
• mapbase — physical address of the MMIO registers.
• mck — the peripheral bus clock hooked up to the MMC controller.
• dev — device associated with the MMC controller.
• pdata — per-slot configuration data.
• slot — slots sharing this MMC controller.
• caps — MCI capabilities depending on MCI version.
• prepare_data — function to setup MCI before data transfer which depends on MCI capabilities.
• submit_data — function to start data transfer which depends on MCI capabilities.
• stop_transfer — function to stop data transfer which depends on MCI capabilities.

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💜 Description 💜

okay so the whole personality of this struct is locking, and it is not playing around about it 😭

🔒 Locking 🔒

lock is a softirq-safe spinlock protecting queue as well as cur_slot, mrq and state. These must always be updated at the same time while holding lock. no splitting the group chat update, bestie 🫶

lock also protects mode_reg and need_clock_update since these are used to synchronize mode register updates with the queue processing.

The mrq field of struct atmel_mci_slot is also protected by lock, and must always be written at the same time as the slot is added to queue.

pending_events and completed_events are accessed using atomic bit operations, so they don't need any locking. slay for them ✨

None of the fields touched by the interrupt handler need any locking. However, ordering is important: Before EVENT_DATA_ERROR or EVENT_DATA_COMPLETE is set in pending_events, all data-related interrupts must be disabled and data_status updated with a snapshot of SR. Similarly, before EVENT_CMD_COMPLETE is set, the CMDRDY interrupt must be disabled and cmd_status updated with a snapshot of SR, and before EVENT_XFER_COMPLETE can be set, the bytes_xfered field of data must be written. This is ensured by using barriers. do not skip the barrier order, fr fr 💀

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🦋 SEE ALSO 🦋

• Kernel file ./drivers/mmc/host/atmel-mci.c
• struct mci_slot_pdata(9)
• struct atmel_mci_slot(9)

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mwah 💋 source ./drivers/mmc/host, October 2026, page struct atmel_mci(9) — that's the whole footer vibe, bestie 🫶🌈