1SPI/QSPI Dual flash connection modes: 2===================================== 3 4This describes how SPI/QSPI flash memories are connected to a given 5controller in a single chip select line. 6 7Current spi_flash framework supports, single flash memory connected 8to a given controller with single chip select line, but there are some 9hw logics(ex: xilinx zynq qspi) that describes two/dual memories are 10connected with a single chip select line from a controller. 11 12"dual_flash" from include/spi.h describes these types of connection mode 13 14Possible connections: 15-------------------- 16SF_SINGLE_FLASH: 17 - single spi flash memory connected with single chip select line. 18 19 +------------+ CS +---------------+ 20 | |----------------------->| | 21 | Controller | I0[3:0] | Flash memory | 22 | SPI/QSPI |<======================>| (SPI/QSPI) | 23 | | CLK | | 24 | |----------------------->| | 25 +------------+ +---------------+ 26 27SF_DUAL_STACKED_FLASH: 28 - dual spi/qspi flash memories are connected with a single chipselect 29 line and these two memories are operating stacked fasion with shared buses. 30 - xilinx zynq qspi controller has implemented this feature [1] 31 32 +------------+ CS +---------------+ 33 | |---------------------->| | 34 | | I0[3:0] | Upper Flash | 35 | | +=========>| memory | 36 | | | CLK | (SPI/QSPI) | 37 | | | +---->| | 38 | Controller | CS | | +---------------+ 39 | SPI/QSPI |------------|----|---->| | 40 | | I0[3:0] | | | Lower Flash | 41 | |<===========+====|====>| memory | 42 | | CLK | | (SPI/QSPI) | 43 | |-----------------+---->| | 44 +------------+ +---------------+ 45 46 - two memory flash devices should has same hw part attributes (like size, 47 vendor..etc) 48 - Configurations: 49 on LQSPI_CFG register, Enable TWO_MEM[BIT:30] on LQSPI_CFG 50 Enable U_PAGE[BIT:28] if U_PAGE flag set - upper memory 51 Disable U_PAGE[BIT:28] if U_PAGE flag unset - lower memory 52 - Operation: 53 accessing memories serially like one after another. 54 by default, if U_PAGE is unset lower memory should accessible, 55 once user wants to access upper memory need to set U_PAGE. 56 57Note: Technically there is only one CS line from the controller, but 58zynq qspi controller has an internal hw logic to enable additional CS 59when controller is configured for dual memories. 60 61[1] http://www.xilinx.com/support/documentation/user_guides/ug585-Zynq-7000-TRM.pdf 62 63-- 64Jagannadha Sutradharudu Teki <jaganna@xilinx.com> 6505-01-2014. 66