• Chen-Yu Tsai's avatar
    serial: 8250_dw: Add support for deferred probing · c8ed99d4
    Chen-Yu Tsai authored
    The 8250_dw driver fails to probe if the specified clock isn't
    registered at probe time. Even if a clock frequency is given,
    the required clock might be gated because it wasn't properly
    enabled.
    
    This happened to me when the device is registered through DT,
    and the clock was part of an MFD, the PRCM found on A31 and A23
    SoCs. Unlike core clocks that are registered with OF_CLK_DECLARE,
    which happen almost immediately after the kernel starts, the
    clocks are registered as sub-devices of the PRCM MFD platform
    device. Even though devices are registered in the order they are
    found in the DT, the drivers are registered in a different,
    arbitrary order. It is possible that the 8250_dw driver is
    registered, and thus associated with the device and probed, before
    the clock driver is registered and probed.
    
    8250_dw then reports unable to get the clock, and fails. Without
    a working console, the kernel panics.
    
    This patch adds support for deferred probe handling for the clock
    and reset controller. It also fixes the cleanup path if
    serial8250_register_8250_port fails.
    Signed-off-by: default avatarChen-Yu Tsai <wens@csie.org>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    c8ed99d4
8250_dw.c 13.6 KB