Re: OMAPDSS: omap5 SYNC_LOST error with DPI/LCD

[Archit Taneja <archit@ti.com>]

Hi,

On Friday 09 May 2014 02:07 PM, Patil, Vikash wrote:
> Hi Archit,
>
> With CONFIG_OMAP2_DSS_MIN_FCK_PER_PCK to 4, mode becomes invalid and can't launch kmscube.
>
> [    0.847015] [drm:omap_connector_mode_valid], connector: mode invalid: 14:"1280x480" 60 40500 1280 1350 1365 1366 480 491 492 494 0x48 0x0
> [    0.847045] [drm:drm_mode_debug_printmodeline], Modeline 14:"1280x480" 60 40500 1280 1350 1365 1366 480 491 492 494 0x48 0x0
> [    0.847045] [drm:drm_mode_prune_invalid], Not using 1280x480 mode -2
> [    0.847076] No connectors reported connected with modes

Maybe the driver wasn't able to calculate 40.5 Mhz with 
CONFIG_OMAP2_DSS_MIN_FCK_PER_PCK=4, the complete logs would help here.

>
>
>>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
>
> Is this because CONFIG_OMAP2_DSS_DSI is not set? Not sure this also needs to enable as I am using 3.4.25 kernel.

Yes, this config is needed to derive pixel clock from DSI PLL.

>
> Is there any dependencies with TDF19988 (HDMI converter)? Like missing support or driver?

A bad configuration of TDF19988 shouldn't result in a sync lost. Sync 
losts are more or less internal to the Display Controller(DISPC).


A dump of the DSS and DISPC registers will help here.

Could you set CONFIG_OMAP2_DSS_DEBUGFS to 'y', and share the output of 
the just after the error occurs?

cat /sys/kernel/debug/omapdss/dss
cat /sys/kernel/debug/omapdss/dispc

Archit

> Regards,
> Vikash
>
> -----Original Message-----
> From: dri-devel [mailto:dri-devel-bounces@lists.freedesktop.org] On Behalf Of Archit Taneja
> Sent: Friday, May 09, 2014 12:09 PM
> To: Vikas Patil
> Cc: Valkeinen, Tomi; dri-devel@lists.freedesktop.org
> Subject: Re: OMAPDSS: omap5 SYNC_LOST error with DPI/LCD
>
> 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
>> https://gitorious.org/thierryreding/linux/source/e7792ce2da5ded80861db787ace9b57ecf7bc96c:drivers/gpu/drm/i2c/tda998x_drv.c.
>> 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@gmail.com
>> <mailto:vikasmpatil@gmail.com>> 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
> above.
>
> Archit
>
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