OMAPDSS: omap5 SYNC_LOST error with DPI/LCD

Archit Taneja archit at
Thu May 8 23:38:51 PDT 2014

Hi Vikas,

On Friday 09 May 2014 11:54 AM, Vikas Patil wrote:
> Hi,
> Forgot to mention, DPI pins are connected to TDF19988 chip for HDMI
> conversion.
> I have build the driver for it from
> Is this the correct driver for it? Also I am trying to use the
> generic-dpi-panel driver for this. it seems I also need to add support
> for TDF19988 somewhere in omapdrm or lcd/panel driver by calling
> drm_i2c_encoder_init. Could you please give inputs, how should I proceed
> further?
> Thanks & Regards,
> Vikash
> On Thu, May 8, 2014 at 3:37 PM, Vikas Patil <vikasmpatil at
> <mailto:vikasmpatil at>> wrote:
>     Hi,
>     I am working on to enable the second display output for customized
>     OMAP5 based platform and linux 3.4.25. First display which is
>     HDMI/tv is working fine. Second display out is coming via DPI
>     interface. To enable DPI interface I enabled CONFIG_OMAP2_DSS_DPI
>     and CONFIG_PANEL_GENERIC_DPI and added that in omap_dss_device and
>     omap_dss_board_info and removed the HDMI device and disabled
>     CONFIG_OMAP5_DSS_HDMI. With his kernel seems to be booting
>     correctly, however when I try to run kmscube app and it seems to be
>     running, noticing following error and till now nothing on display.
>     Could you give some inputs to debug this? Is this following error
>     due to which not getting anything on display?

 From the logs, one thing which looks like a problem is that the DPI 
driver isn't using a DSI PLL to generate a pixel clock of 40.5 Mhz for 
the 1280x480 panel. It's trying to change DSS_FCK to get the desired 
clock. This won't work well if we start doing scaling. And in genral, 
it's always good to have DSS_FCK a bit higher than the pixel clocks of 
all the panels connected to DSS.

Could you try to set the value of CONFIG_OMAP2_DSS_MIN_FCK_PER_PCK to 4, 
and tell what happens? The correct solution would be to figure out why 
it isn't using the DSI PLL, but we could start with changing the config 


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