• Jacopo Mondi's avatar
    drm: rcar-du: Improve non-DPLL clock selection · 8c74c456
    Jacopo Mondi authored
    DU channels not equipped with a DPLL use an SoC internal (provided by
    the CPG) or external clock source combined with a DU internal divider to
    generate the desired output dot clock frequency.
    
    The current clock selection procedure does not fully exploit the ability
    of external clock sources to generate the exact dot clock frequency by
    themselves, but relies instead on tuning the internal DU clock divider
    only, resulting in a less precise clock generation process.
    
    When possible, and desirable, ask the external clock source for the
    exact output dot clock frequency, and select the clock source that
    produces the frequency closest to the desired output dot clock.
    
    This patch specifically targets platforms (like Salvator-X[S] and ULCBs)
    where the DU's input dotclock.in is generated by the versaclock VC5
    clock source, which is capable of generating the exact rate the DU needs
    as pixel clock output.
    
    This patch fixes higher resolution modes which requires an high pixel
    clock output currently not working on non-HDMI DU channel (such as
    1920x1080@60Hz on the VGA output).
    
    Fixes: 1b30dbde
    
     ("drm: rcar-du: Add support for external pixel clock")
    Signed-off-by: default avatarJacopo Mondi <jacopo@jmondi.org>
    [Factor out code to a helper function]
    Signed-off-by: default avatarLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
    Acked-by: default avatarJacopo Mondi <jacopo+renesas@jmondi.org>
    8c74c456
rcar_du_crtc.c 29.7 KB