• Stephen Street's avatar
    [PATCH] spi: stabilize PIO mode transfers on PXA2xx systems · 8d94cc50
    Stephen Street authored
    Stabilize PIO mode transfers against a range of word sizes and FIFO
    thresholds and fixes word size setup/override issues.
    
    1) 16 and 32 bit DMA/PIO transfers broken due to timing differences.
    2) Potential for bad transfer counts due to transfer size assumptions.
    3) Setup function broken is multiple ways.
    4) Per transfer bit_per_word changes break DMA setup in pump_tranfers.
    5) False positive timeout are not errors.
    6) Changes in pxa2xx_spi_chip not effective in calls to setup.
    7) Timeout scaling wrong for PXA255 NSSP.
    8) Driver leaks memory while busy during unloading.
    
    Known issues:
    
    SPI_CS_HIGH and SPI_LSB_FIRST settings in struct spi_device are not handled.
    
    Testing:
    
    This patch has been test against the "random length, random bits/word,
    random data (verified on loopback) and stepped baud rate by octaves
    (3.6MHz to 115kHz)" test.  It is robust in PIO mode, using any
    combination of tx and rx thresholds, and also in DMA mode (which
    internally computes the thresholds).
    
    Much thanks to Ned Forrester for exhaustive reviews, fixes and testing.
    The driver is substantially better for his efforts.
    Signed-off-by: default avatarStephen Street <stephen@streetfiresound.com>
    Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    8d94cc50
pxa2xx 8.35 KB