• Thor Thayer's avatar
    spi: dw: Fix dynamic speed change. · 982b1001
    Thor Thayer authored
    commit 0a8727e6 upstream.
    
    An IOCTL call that calls spi_setup() and then dw_spi_setup() will
    overwrite the persisted last transfer speed. On each transfer, the
    SPI speed is compared to the last transfer speed to determine if the
    clock divider registers need to be updated (did the speed change?).
    This bug was observed with the spidev driver using spi-config to
    update the max transfer speed.
    
    This fix: Don't overwrite the persisted last transaction clock speed
    when updating the SPI parameters in dw_spi_setup(). On the next
    transaction, the new speed won't match the persisted last speed
    and the hardware registers will be updated.
    On initialization, the persisted last transaction clock
    speed will be 0 but will be updated after the first SPI
    transaction.
    
    Move zeroed clock divider check into clock change test because
    chip->clk_div is zero on startup and would cause a divide-by-zero
    error. The calculation was wrong as well (can't support odd #).
    Reported-by: default avatarVlastimil Setka <setka@vsis.cz>
    Signed-off-by: default avatarVlastimil Setka <setka@vsis.cz>
    Signed-off-by: default avatarThor Thayer <tthayer@opensource.altera.com>
    Signed-off-by: default avatarMark Brown <broonie@kernel.org>
    Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
    982b1001
spi-dw.c 21.8 KB