Re: [PATCH 1/4] OMAPDSS: Fix DSS clock multiplier issue on 3703 and probably 3630

On Fri, May 9, 2014 at 9:38 AM, Tomi Valkeinen [off-list ref] wrote:

On 30/04/14 02:52, Tony Lindgren wrote:

quoted

Otherwise we can get often errors like the following and the
display won't come on:

omapdss APPLY error: FIFO UNDERFLOW on gfx, disabling the overlay
omapdss APPLY error: SYNC_LOST on channel lcd, restarting
the output with video overlays disabled

There are some earlier references to this issue:

http://www.spinics.net/lists/linux-omap/msg59511.html
http://www.spinics.net/lists/linux-omap/msg59724.html

resend - my client had HTML enabled...

FWIW: I have had issues long time ago [1]. With mainline 3.14.3 I had
still the reboot problem on old 600MHz OMAP 3530. Applying this patch
solved the issues. For other versions I had no chance to reproduce the
original wakup issue mentioned in old thread

[1] http://marc.info/?l=linux-omap&m6250904607413&w=2

Andreas

Those don't sound like the same issue, but it's hard to say. What kind
of clock rates do you get? Cat you paste debugfs/omapdss/clk, with and
without this patch?

What resolution do you have? If it's a very high resolution (say, DVI
output to a monitor), it could just be an issue of
not-enough-memory-bandwidth.

quoted

It seems that it's safe to set the lower values even for 3630.
If we can confirm that 3630 works with the higher values
reliably we can add further detection.

Signed-off-by: Tony Lindgren <tony@atomide.com>
---
 drivers/video/fbdev/omap2/dss/dss.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/video/fbdev/omap2/dss/dss.c b/drivers/video/fbdev/omap2/dss/dss.c
index d55266c..ad6561f 100644
--- a/drivers/video/fbdev/omap2/dss/dss.c
+++ b/drivers/video/fbdev/omap2/dss/dss.c

@@ -707,9 +707,10 @@ static const struct dss_features omap34xx_dss_feats __initconst = {
      .dpi_select_source      =       &dss_dpi_select_source_omap2_omap3,
 };

+/* Supposedly 3630 can use div 32 mult 2, but that needs to be rechecked */
 static const struct dss_features omap3630_dss_feats __initconst = {
-     .fck_div_max            =       32,
-     .dss_fck_multiplier     =       1,
+     .fck_div_max            =       16,
+     .dss_fck_multiplier     =       2,

These values tell about the clock hardware, they are not settings that
can be changed to change the clock. OMAP3630 has a fixed x2 multiplier
and a divider with maximum value of 16.

 Tomi