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

* Tomi Valkeinen [off-list ref] [140509 00:39]:

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

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?

Without this patch:
# cat /sys/kernel/debug/omapdss/clk 
[   24.833831] DSS: dss_runtime_get
[   24.837554] DSS: dss_runtime_put
[   24.840972] DISPC: dispc_runtime_get
[   24.844757] DISPC: dispc_runtime_put
- DSS -
DSS_FCK (DSS1_ALWON_FCLK) = 57600000
- DISPC -
dispc fclk source = DSS_FCK (DSS1_ALWON_FCLK)
fck             57600000        
- LCD -
LCD clk source = DSS_FCK (DSS1_ALWON_FCLK)
lck             57600000        lck div 1
pck             19200000        pck div 3


With this patch:
# cat /sys/kernel/debug/omapdss/clk 
[   34.580688] DSS: dss_runtime_get
[   34.584197] DSS: dss_runtime_put
[   34.587768] DISPC: dispc_runtime_get
[   34.591552] DISPC: dispc_runtime_put
- DSS -
DSS_FCK (DSS1_ALWON_FCLK) = 108000000
- DISPC -
dispc fclk source = DSS_FCK (DSS1_ALWON_FCLK)
fck             108000000       
- LCD -
LCD clk source = DSS_FCK (DSS1_ALWON_FCLK)
lck             108000000       lck div 1
pck             18000000        pck div 6
 

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.

This is just the 3730-evm with the Sharp VGA panel mentioned in
this series.
 

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