possible bug in descriptors allocation - NIMU Eth driver

Ran Yaniv

Hi,

The NIMU ethernet driver provided in the PDK of C6670 is compiled with the following defines (defined in resource_mgr.h):

#define NIMU_NUM_TX_DESC 16u /**< Maximum number of TX descriptors used by NIMU */

#define NIMU_NUM_RX_DESC 18u /**< Maximum number of RX descriptors used by NIMU */

#define MAX_NUM_NIMU_DESC (NIMU_NUM_TX_DESC + NIMU_NUM_RX_DESC) /**< Maximum number of descriptors used bye NIMU */

The number of descriptors allocated during Qmss_insertMemoryRegion() is therefore not a power of 2.

As a result it is not possible to add more Memory Regions afterwards, unless it is done manually by specifying the explicit memory region index in memRegion field and setting start_index to leave a hole until the next power of 2.

An error -129 is returned when adding a memory region using memRegion=Qmss_MemRegion_MEMORY_REGION_NOT_SPECIFIED, .

I'd suggest changing the number of descriptors in the NIMU driver so that it is a power of 2.

Regards,

Ran

over 14 years ago

0 tscheck over 13 years ago

TI__Mastermind 23525 points

Ran,

You are right that it needs to be a power of 2 in size, within the resource_mgr.h. We are already making changes to this for future release of the MCSDK to increase the NIMU_NUM_RX_DESC number for performance reasons. Please take a look at the following post for more details on this and other changes:

http://e2e.ti.com/support/dsp/c6000_multi-core_dsps/f/639/p/134675/502440.aspx#502440

Regards,

Travis

0 Ran Yaniv over 13 years ago in reply to tscheck

Intellectual 645 points

Hi Travis,

Thanks. I'll also give the proposed changes a try. Do you expect that the short-packet latency will improve dramatically? We currently have serious latency issues receiving such messages.

Thanks

Ran

0 tscheck over 13 years ago in reply to Ran Yaniv

TI__Mastermind 23525 points

I'll have to ask. What are you currently measuring for latency?

Regards,

Travis

0 Ran Yaniv over 13 years ago in reply to tscheck

Intellectual 645 points

Hi Travis,

We were observing latencies on the order of 1-1.2 msec. This was in the case of low traffic volume and low packet rate but also with low latency requirement.

We figured this out however, the issue had to do with the TimerLoadCount accumulator configuration in the NIMU driver, which was set to 40 in the driver supplied with the PDK (40 * 25usec = 1msec ...).

Regards

Ran

0 tscheck over 13 years ago in reply to Ran Yaniv

TI__Mastermind 23525 points

Ahh, good find. So you can just disable the pacing with Qmss_AccPacingMode_NONE, or adjust the TimerLoadCount to suit your needs.

Regards,

Travis

0 Santosh Pinto over 13 years ago in reply to tscheck

Expert 1010 points

Hello tscheck,

Im too facing the same issue with packets getting dropped and not being able to deliver it to the application by the PDSP accumulator interrupt.

I want to receive packets at the Ethernet PHY of the evmc6670 at regular intervals of 1ms and less than that, so i have set the RX_INT_THRESHOLD value in NIMU driver to "1" which means that the interrupt by the PDSP will be enabled when it recieves one packet in the interrupt queue, and have kept the TimerLoadCount to "40" itself.

Even in these settings , ive observed that packets tend to get missed at the evm C6670 after some runs.

Ive even posted the same issue at

http://e2e.ti.com/support/embedded/bios/f/355/p/162523/674656.aspx#674656

Pls help me with this issue. ITs been pending from a long time, and suggest me an appropriate setting so as to not miss any packets at the NIMU.

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possible bug in descriptors allocation - NIMU Eth driver