• Tomi Valkeinen's avatar
    OMAPDSS: HDMI: PHY burnout fix · c49d005b
    Tomi Valkeinen authored
    A hardware bug in the OMAP4 HDMI PHY causes physical damage to the board
    if the HDMI PHY is kept powered on when the cable is not connected.
    
    This patch solves the problem by adding hot-plug-detection into the HDMI
    IP driver. This is not a real HPD support in the sense that nobody else
    than the IP driver gets to know about the HPD events, but is only meant
    to fix the HW bug.
    
    The strategy is simple: If the display device is turned off by the user,
    the PHY power is set to OFF. When the display device is turned on by the
    user, the PHY power is set either to LDOON or TXON, depending on whether
    the HDMI cable is connected.
    
    The reason to avoid PHY OFF when the display device is on, but the cable
    is disconnected, is that when the PHY is turned OFF, the HDMI IP is not
    "ticking" and thus the DISPC does not receive pixel clock from the HDMI
    IP. This would, for example, prevent any VSYNCs from happening, and
    would thus affect the users of omapdss. By using LDOON when the cable is
    disconnected we'll avoid the HW bug, but keep the HDMI working as usual
    from the user's point of view.
    Signed-off-by: default avatarTomi Valkeinen <tomi.valkeinen@ti.com>
    c49d005b
ti_hdmi_4xxx_ip.c 35.3 KB