• Laurentiu-Cristian Duca's avatar
    am335x (beaglebone black) omap4 spi real-time driver. · 3d8d59f9
    Laurentiu-Cristian Duca authored
    spi-omap2-mcspi-rt.c:
    I/O handling is lifted from  omap2/4 mcspi linux driver.
    The code follows the model in spi-bcm2835.c.
    The theoretical maximum spi frequency of am335x omap4 is 48MHz,
    and the driver practical maximum frequency is limited to 40MHz.
    The omap4 maximum fifo queue size is 64 bytes,
    but when the transfer implies both sending and receiving
    it is limited to 32, so, in the driver things are kept simple:
    max 32 for tx and max 32 for rx.
    When the driver must transfer N bytes
    then ((int)(N/32))*32 bytes are transfered with fifo queue size 32
    and (N mod 32) bytes are transfered with fifo queue size (N mod 32);
    between fifo setup, the slave chip select line is kept active
    by using the FORCE bit in the channel configuration register.
    Signed-off-by: default avatarLaurentiu-Cristian Duca <laurentiu.duca@gmail.com>
    Signed-off-by: Jan Kiszka's avatarJan Kiszka <jan.kiszka@siemens.com>
    3d8d59f9
spi-omap2-mcspi-rt.c 26.8 KB