On 2012-10-31 08:54, Archit Taneja wrote:

On Tuesday 30 October 2012 09:40 PM, Tomi Valkeinen wrote:

quoted

dss.c currently exposes functions to configure the dispc source clock
and lcd source clock. There are configured separately from the output
drivers.

However, there is no safe way for the output drivers to handle dispc
clock, as it's shared between the outputs. Thus, if, say, the DSI driver
sets up DSI PLL and configures both the dispc and lcd clock sources to
that DSI PLL, the resulting dispc clock could be too low for, say, HDMI.

Thus the output drivers should really only be concerned about the lcd
clock, which is what the output drivers actually use. There's lot to do
to clean up the dss clock handling, but this patch takes one step
forward and removes the use of dss_select_dispc_clk_source() from the
output drivers.

After this patch, the output drivers only configure the lcd source
clock. On omap4+ the dispc src clock is never changed from the default
PRCM source. On omap3, where the dispc and lcd clocks are actually the
same, setting the lcd clock source sets the dispc clock source.

Maybe we could have one call to dss_select_dispc_clk_source() in
omap_dsshw_porbe(). This is not necessary now, but if we support a
splash screen on bootloader, and skip the hwmod resets, we might want to
switch back our dispc clock source to PRCM if the output drivers don't
to it. This is just a point though, we don't necessarily need it right now.

If we're showing the image from the bootloader, we can't change the
clock sources if we want to keep the display working. We either need to
accept and use the config the bootloader did, or reset the dss and start
over with our config.

But you're right, even if we don't support the splash screen from the
bootloader, we can't be sure if the dss hw was reset or not, and what
the clock source is. So it probably is safer to set the clock source at
probe time (and actually all other configs also).

 Tomi