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Diffstat (limited to 'doc/driver-model/UDM-spi.txt')
| -rw-r--r-- | doc/driver-model/UDM-spi.txt | 200 |
1 files changed, 0 insertions, 200 deletions
diff --git a/doc/driver-model/UDM-spi.txt b/doc/driver-model/UDM-spi.txt deleted file mode 100644 index 9ba0f84..0000000 --- a/doc/driver-model/UDM-spi.txt +++ /dev/null @@ -1,200 +0,0 @@ -The U-Boot Driver Model Project -=============================== -SPI analysis -============ -Viktor Krivak <viktor.krivak@gmail.com> -2012-03-03 - -I) Overview ------------ - - 1) The SPI driver - ----------------- - - At this moment U-Boot provides standard API that consist of 7 functions: - - void spi_init(void); - struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs, - unsigned int max_hz, unsigned int mode); - void spi_free_slave(struct spi_slave *slave); - int spi_claim_bus(struct spi_slave *slave); - void spi_release_bus(struct spi_slave *slave); - int spi_xfer(struct spi_slave *slave, unsigned int bitlen, - const void *dout, void *din, unsigned long flags); - int spi_cs_is_valid(unsigned int bus, unsigned int cs); - void spi_cs_activate(struct spi_slave *slave); - void spi_cs_deactivate(struct spi_slave *slave); - void spi_set_speed(struct spi_slave *slave, uint hz); - - Method spi_init() is usually empty. All necessary configuration are sets by - spi_setup_slave(). But this configuration is usually stored only in memory. - No real hardware sets are made. All hardware settings are provided by method - spi_claim_bus(). This method claims the bus and it can't be claimed again - until it's release. That's mean all calls of method spi_claim_bus() will - fail. But lots of cpu implementation don't meet this behaviour. - Method spi_release_bus() does exact opposite. It release bus directly by - some hardware sets. spi_free_slave() only free memory allocated by - spi_setup_slave(). Method spi_xfer() do actually read and write operation - throw specified bus and cs. Other methods are self explanatory. - - 2) Current limitations - ---------------------- - - Theoretically at this moment api allows use more then one bus per device at - the time. But in real this can be achieved only when all buses have their - own base addresses in memory. - - -II) Approach ------------- - - 1) Claiming bus - --------------- - - The current api cannot be used because struct spi_slave have to be in - private data. In that case user are prohibited to use different bus on one - device at same time. But when base memory address for bus are different. - It's possible make more instance of this driver. Otherwise it can't can be - done because of hardware limitation. - - 2) API change - ------------- - - Method spi_init() is moved to probe. Methods spi_setup_slave() and - spi_claim_bus() are joined to one method. This method checks if desired bus - exists and is available then configure necessary hardware and claims bus. - Method spi_release_bus() and spi_free_slave() are also joined to meet this - new approach. Other function remain same. Only struct spi_slave was change - to instance. - - struct ops { - int (*spi_request_bus)(struct instance *i, unsigned int bus, - unsigned int cs, unsigned int max_hz, - unsigned int mode); - void (*spi_release_bus)(struct instance *i); - int (*spi_xfer) (struct instance *i, unsigned int bitlen, - const void *dout, void *din, unsigned long flags); - int (*spi_cs_is_valid)(struct instance *i, unsigned int bus, - unsigned int cs); - void (*spi_cs_activate)(struct instance *i); - void (*spi_cs_deactivate)(struct instance *i); - void (*spi_set_speed)(struct instance *i, uint hz); - } - - 3) Legacy API - ------------- - - To easy conversion of the whole driver. Original and new api can exist next - to each other. New API is designed to be only a wrapper that extracts - necessary information from private_data and use old api. When driver can - use more than one bus at the time. New API require multiple instance. One - for each bus. In this case spi_slave have to be copied in each instance. - - 4) Conversion TIME-LINE - ----------------------- - - To prevent build corruption api conversion have to be processed in several - independent steps. In first step all old API methods are renamed. After that - new API and core function are implemented. Next step is conversion of all - board init methods to set platform data. After all these steps it is possible - to start conversion of all remaining calls. This procedure guarantees that - build procedure and binaries are never broken. - -III) Analysis of in-tree drivers --------------------------------- - - altera_spi.c - ------------ - All methods have designated structure. Simple conversion possible. - - andes_spi.c - ----------- - All methods have designated structure. Simple conversion possible. - - andes_spi.h - ----------- - Support file for andes_spi.c. No conversion is needed. - - armada100_spi.c - --------------- - All methods have designated structure. Simple conversion possible. - - atmel_dataflash_spi.c - --------------------- - Wrong placement. Will be moved to another location. - - atmel_spi.c - ----------- - Supports more than one bus. Need some minor change. - - atmel_spi.h - ----------- - Support file for andes_spi.c. No conversion is needed. - - bfin_spi.c - ---------- - Supports more than one bus. Need some minor change. - - cf_spi.c - -------- - Cooperate with some cpu specific methods from other files. Hard conversion. - - davinci_spi.c - ------------- - All methods have designated structure. Simple conversion possible. - - davinci_spi.h - ------------- - Support file for davinci_spi.h. No conversion is needed. - - fsl_espi.c - ---------- - All methods have designated structure. Simple conversion possible. - - kirkwood_spi.c - -------------- - All methods have designated structure. Simple conversion possible. - - mpc8xxx_spi.c - ------------- - All methods have designated structure. Simple conversion possible. - - mpc52xx_spi.c - ------------- - All methods have designated structure. Simple conversion possible. - - mxc_spi.c - --------- - All methods have designated structure. Simple conversion possible. - - mxs_spi.c - --------- - All methods have designated structure. Simple conversion possible. - - oc_tiny_spi.c - ------------- - Supports more than one bus. Need some minor change. - - omap3_spi.c - ----------- - Supports more than one bus. Need some minor change. - - omap3_spi.h - ----------- - Support file for omap3_spi.c. No conversion is needed. - - sh_spi.c - -------- - All methods have designated structure. Simple conversion possible. - - sh_spi.h - -------- - Support file for sh_spi.h. No conversion is needed. - - soft_spi.c - ---------- - Use many board specific method linked from other files. Need careful debugging. - - tegra2_spi.c - ------------ - Some hardware specific problem when releasing bus. |