Hello Forum,

i am using a vdr headless server with 3 Technisat Skystar USB tuners for satellite television streaming.

Before i used a raspberry pi 2 but because of limitations with its ethernet bandwith i went to odroid c2.

System is now armbian with self compiled vdr with vnsi plugin, both out of git repo.

System runs fine but after some hours (8h) a sporadic failure occurs and (USB?) system becomes unusable,

To get the 3 dvb-s2 tuners running i increased the urb pool (USB request block) with kernel parameter "coherent_pool=6M" in boot.ini.

I calculated that every of all 3 instances of driver needs about 512kB of USB buffer memory, without the option the first instance fails with error -12 (ENOMEM).

At first i put an option "coherent_pool=32M" to test but it seemed that this was ignored without any message.

I found a hint in another forum and tried 6M and that seemed to be taken and to be enough for my 3 tuner devices.

 

My first questions is: what are the limits for this parameter coherent_pool and what is the default value ?

 

Second: what can i do to increase stability of USB ?

 

Here the syslog after some hours:

WARN::urb_dequeue:780: urb->hcpriv == NULL; urb = ffffffc07a0c9000 status=-2

 

and then lots of

 

driver and application errors because of usb action errors:

dvb-usb2: i2c-error: out failed 68 = -110

 

 

Hello,

is there someone in this forum who can tell about this "coherent_pool" ?

Is there some adjustment needed in uboot to reseve some DRAM for this pool ?

Until now i only found that default size is 256kB and this is much too small for some multimedia devices.

 

If i take "coherent_pool=8M" the system not even runs until video chip initialization, hdmi stays black.

If set it to 1M system boots.

What are the limits, is there something to adjust in uboot ?

Thanks

  Thomas