tree 6b53d49b3373a5118b719ebce07d39bb384ef85c
parent aa74274b464d4aa24703963ac89a0ee942d5d267
author Tomi Valkeinen <tomi.valkeinen@ti.com> 1326791397 +0200
committer Tomi Valkeinen <tomi.valkeinen@ti.com> 1327578696 +0200

OMAPDSS: HDMI: PHY burnout fix

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: Tomi Valkeinen <tomi.valkeinen@ti.com>