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Diffstat (limited to 'doc/driver-model/UDM-mmc.txt')
| -rw-r--r-- | doc/driver-model/UDM-mmc.txt | 319 |
1 files changed, 0 insertions, 319 deletions
diff --git a/doc/driver-model/UDM-mmc.txt b/doc/driver-model/UDM-mmc.txt deleted file mode 100644 index 97f83a7..0000000 --- a/doc/driver-model/UDM-mmc.txt +++ /dev/null @@ -1,319 +0,0 @@ -The U-Boot Driver Model Project -=============================== -MMC system analysis -=================== -Marek Vasut <marek.vasut@gmail.com> -2012-02-25 - -I) Overview ------------ - -The MMC subsystem is already quite dynamic in it's nature. It's only necessary -to flip the subsystem to properly defined API. - -The probing process of MMC drivers start by calling "mmc_initialize()", -implemented by MMC framework, from the architecture initialization file. The -"mmc_initialize()" function in turn calls "board_mmc_init()" function and if -this doesn't succeed, "cpu_mmc_init()" function is called. It is important to -note that both of the "*_mmc_init()" functions have weak aliases to functions -which automatically fail. - -Both of the "*_mmc_init()" functions though serve only one purpose. To call -driver specific probe function, which in turn actually registers the driver with -MMC subsystem. Each of the driver specific probe functions is currently done in -very ad-hoc manner. - -The registration with the MMC subsystem is done by calling "mmc_register()", -whose argument is a runtime configured structure of information about the MMC -driver. Currently, the information structure is intermixed with driver's internal -data. The description of the structure follows: - -struct mmc { - /* - * API: Allows this driver to be a member of the linked list of all MMC drivers - * registered with MMC subsystem - */ - struct list_head link; - - /* DRIVER: Name of the registered driver */ - char name[32]; - - /* DRIVER: Driver's private data */ - void *priv; - - /* DRIVER: Voltages the host bus can provide */ - uint voltages; - - /* API: Version of the card */ - uint version; - - /* API: Test if the driver was already initialized */ - uint has_init; - - /* DRIVER: Minimum frequency the host bus can provide */ - uint f_min; - - /* DRIVER: Maximum frequency the host bus can provide */ - uint f_max; - - /* API: Is the card SDHC */ - int high_capacity; - - /* API: Actual width of the bus used by the current card */ - uint bus_width; - - /* - * DRIVER: Clock frequency to be configured on the host bus, this is read-only - * for the driver. - */ - uint clock; - - /* API: Capabilities of the card */ - uint card_caps; - - /* DRIVER: MMC bus capabilities */ - uint host_caps; - - /* API: Configuration and ID data retrieved from the card */ - uint ocr; - uint scr[2]; - uint csd[4]; - uint cid[4]; - ushort rca; - - /* API: Partition configuration */ - char part_config; - - /* API: Number of partitions */ - char part_num; - - /* API: Transmission speed */ - uint tran_speed; - - /* API: Read block length */ - uint read_bl_len; - - /* API: Write block length */ - uint write_bl_len; - - /* API: Erase group size */ - uint erase_grp_size; - - /* API: Capacity of the card */ - u64 capacity; - - /* API: Descriptor of this block device */ - block_dev_desc_t block_dev; - - /* DRIVER: Function used to submit command to the card */ - int (*send_cmd)(struct mmc *mmc, - struct mmc_cmd *cmd, struct mmc_data *data); - - /* DRIVER: Function used to configure the host */ - void (*set_ios)(struct mmc *mmc); - - /* DRIVER: Function used to initialize the host */ - int (*init)(struct mmc *mmc); - - /* DRIVER: Function used to report the status of Card Detect pin */ - int (*getcd)(struct mmc *mmc); - - /* - * DRIVER: Maximum amount of blocks sent during multiblock xfer, - * set to 0 to autodetect. - */ - uint b_max; -}; - -The API above is the new API used by most of the drivers. There're still drivers -in the tree that use old, legacy API though. - -2) Approach ------------ - -To convert the MMC subsystem to a proper driver model, the "struct mmc" -structure will have to be properly split in the first place. The result will -consist of multiple parts, first will be the structure defining operations -provided by the MMC driver: - -struct mmc_driver_ops { - /* Function used to submit command to the card */ - int (*send_cmd)(struct mmc *mmc, - struct mmc_cmd *cmd, struct mmc_data *data); - /* DRIVER: Function used to configure the host */ - void (*set_ios)(struct mmc *mmc); - /* Function used to initialize the host */ - int (*init)(struct mmc *mmc); - /* Function used to report the status of Card Detect pin */ - int (*getcd)(struct mmc *mmc); -} - -The second part will define the parameters of the MMC driver: - -struct mmc_driver_params { - /* Voltages the host bus can provide */ - uint32_t voltages; - /* Minimum frequency the host bus can provide */ - uint32_t f_min; - /* Maximum frequency the host bus can provide */ - uint32_t f_max; - /* MMC bus capabilities */ - uint32_t host_caps; - /* - * Maximum amount of blocks sent during multiblock xfer, - * set to 0 to autodetect. - */ - uint32_t b_max; -} - -And finally, the internal per-card data of the MMC subsystem core: - -struct mmc_card_props { - /* Version of the card */ - uint32_t version; - /* Test if the driver was already initializes */ - bool has_init; - /* Is the card SDHC */ - bool high_capacity; - /* Actual width of the bus used by the current card */ - uint8_t bus_width; - /* Capabilities of the card */ - uint32_t card_caps; - /* Configuration and ID data retrieved from the card */ - uint32_t ocr; - uint32_t scr[2]; - uint32_t csd[4]; - uint32_t cid[4]; - uint16_t rca; - /* Partition configuration */ - uint8_t part_config; - /* Number of partitions */ - uint8_t part_num; - /* Transmission speed */ - uint32_t tran_speed; - /* Read block length */ - uint32_t read_bl_len; - /* Write block length */ - uint32_t write_bl_len; - /* Erase group size */ - uint32_t erase_grp_size; - /* Capacity of the card */ - uint64_t capacity; - /* Descriptor of this block device */ - block_dev_desc_t block_dev; -} - -The probe() function will then register the MMC driver by calling: - - mmc_device_register(struct instance *i, struct mmc_driver_ops *o, - struct mmc_driver_params *p); - -The struct mmc_driver_params will have to be dynamic in some cases, but the -driver shouldn't modify it's contents elsewhere than in probe() call. - -Next, since the MMC drivers will now be consistently registered into the driver -tree from board file, the functions "board_mmc_init()" and "cpu_mmc_init()" will -disappear altogether. - -As for the legacy drivers, these will either be converted or removed altogether. - -III) Analysis of in-tree drivers --------------------------------- - - arm_pl180_mmci.c - ---------------- - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple. - - atmel_mci.c - ----------- - This driver uses the legacy API and should be removed unless converted. It is - probably possbible to replace this driver with gen_atmel_mci.c . No conversion - will be done on this driver. - - bfin_sdh.c - ---------- - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple. - - davinci_mmc.c - ------------- - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple. - - fsl_esdhc.c - ----------- - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple, unless some problem appears due to the FDT - component of the driver. - - ftsdc010_esdhc.c - ---------------- - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple. - - gen_atmel_mci.c - --------------- - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple. - - mmc_spi.c - --------- - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple. - - mv_sdhci.c - ---------- - This is a component of the SDHCI support, allowing it to run on Marvell - Kirkwood chip. It is probable the SDHCI support will have to be modified to - allow calling functions from this file based on information passed via - platform_data. - - mxcmmc.c - -------- - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple. - - mxsmmc.c - -------- - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple. - - omap_hsmmc.c - ------------ - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple. - - pxa_mmc.c - --------- - This driver uses the legacy API and is written in a severely ad-hoc manner. - This driver will be removed in favor of pxa_mmc_gen.c, which is proved to work - better and is already well tested. No conversion will be done on this driver - anymore. - - pxa_mmc_gen.c - ------------- - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple. - - s5p_mmc.c - --------- - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple. - - sdhci.c - ------- - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple, though it'd be necessary to modify this driver - to also support the Kirkwood series and probably also Tegra series of CPUs. - See the respective parts of this section for details. - - sh_mmcif.c - ---------- - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple. - - tegra2_mmc.c - ------------ - Follows the new API and also has a good encapsulation of the whole driver. The - conversion here will be simple. |