66AK2G12: Using EDMA in Linux RT

Hi,

Koichiro Tashiro said:

In their system, both DSP and ARM use EDMA.
Customer afraid there may be access conflicts between DSP and ARM at EDMA.
If so, are there any guideline or sample codes to avoid conflicts?

Did you mean EDMA resource conflict or memory read/write conflict? If EDMA resource conflict is the concern, then just provide different core id to EdmaMgr_init() function for DSP and ARM. If memory read/write conflict is the concern, then you'll need to make sure your application code on DSP and ARM don't access same memory simultaneously.

Koichiro Tashiro said:

It seems EDMA transfer function (EdmaMgr_copy1D1D) is called without calling EDMA initialization function (EdmaMgr_init).
Is this valid? No need to call EdmaMgr_init ?

EdmaMgr_init() is called under the hook by OpenCL monitor during initialization, so those examples do not need to call EdmaMgr_init(). 

Regards,

Jianzhong

Hi Jianzhong,

Jianzhong Xu said:

If EDMA resource conflict is the concern, then just provide different core id to EdmaMgr_init() function for DSP and ARM.

Do you mean both DSP TI RTOS and ARM Linux use the same API (EdmaMgr_Init) ?
It seems RTOS side does not use EdmaMgr.
https://software-dl.ti.com/processor-sdk-rtos/esd/docs/latest/rtos/index_device_drv.html#edma3
Could you clarify this point?
 

Jianzhong Xu said:

EdmaMgr_init() is called under the hook by OpenCL monitor during initialization

Customer wants to know exact code where EdmaMgr_Init() is called.
Could you point me the code location?

Thanks and regards,
Koichiro Tashiro

Hi Koichiro Tashiro,

Linux EDMA usage is handled under the DMA Engine framework by Linux kernel. Any kernel driver which requires DMA would call DMA Engine API to allocate/config/start a DMA channel. The kernel device tree shows mcasp0 uses edma0 channel 24 & 25, mcasp1 uses edma1 channel 48 & 49, mcasp2 uses edma1 channel 50 & 51. You can find detailed information in <sdk>/board-support/linux-rt-.../arch/arm/boot/dts/keystone-k2g.dtsi.

RTOS EDMA usage can be handled either through Framework Component (EDMA manager) or by EDMA LLD. Both have well documented APIs. 

If EDMA is used by both Linux ARM and RTOS DSP, resource conflict can be avoided as long as ARM and DSP don't use the same EDMA resource (different controllers or different channels). However, there is no example for this use case in Processor-SDK and therefore it hasn't been validated. 

Regarding the examples in Linux SDK using EDMA manager that you mentioned, those examples are actually offloaded by OpenCL to run on the DSP. EdmaMgr_init() is called by OpenCL monitor on C66x. Before any of those examples is offloaded to DSP, OpenCL monitor will already have called EdmaMgr_init() under the hook:

• https://git.ti.com/cgit/opencl/ti-opencl/tree/monitor/src/monitor.c#n1198:  when an OpenCL application starts on ARM, it sends a configuration message to OpenCL monitor on C66x, which calls initialize_edmamgr().  It will be initialized only once.
• https://git.ti.com/cgit/opencl/ti-opencl/tree/monitor/src/edma.c#n86: here EdmaMgr_init() is called
• Resource file for configuring K2G edma is here: https://git.ti.com/cgit/opencl/ti-opencl/tree/monitor/src/edma3_tci66ak2g02_cfg.c

Hope this is helpful.

Regards,

Jianzhong

Hi Jianzhong,

Thanks for your detailed answer. There are a few additional questions from customer.

Jianzhong Xu said:

If EDMA is used by both Linux ARM and RTOS DSP, resource conflict can be avoided as long as ARM and DSP don't use the same EDMA resource (different controllers or different channels).

Q3) For example, MMC/SD is mapped to EDMA_1 controller according to TRM Table 10-8.
If ARM uses MMC/SD, Linux ARM needs to use EDMA_1 controller, correct?
In this case, EDMA_0 controller is used by DSP only? Or ARM still can use EDMA_0 controller if channels are different than DSP?
(ex. EDMA_0 ch0 to 31 are used by DSP. EDMA_0 ch32 to 63 are used by ARM.)

Jianzhong Xu said:

Linux EDMA usage is handled under the DMA Engine framework by Linux kernel. Any kernel driver which requires DMA would call DMA Engine API to allocate/config/start a DMA channel. The kernel device tree shows mcasp0 uses edma0 channel 24 & 25, mcasp1 uses edma1 channel 48 & 49, mcasp2 uses edma1 channel 50 & 51. You can find detailed information in <sdk>/board-support/linux-rt-.../arch/arm/boot/dts/keystone-k2g.dtsi.

RTOS EDMA usage can be handled either through Framework Component (EDMA manager) or by EDMA LLD. Both have well documented APIs. 

Q4) Customer understood;
- Linux uses EDMA manager only.
- RTOS can use both EMDA manager and LLD. Which one is recommended, EDMA manger or LLD?

Q5) When EMDA manger is used, src and dst addresses used by EdmaMgr_copy1D1D or EdmaMgr_copy1D2D are virtual address or physical address?

Thanks and regards,
Koichiro Tashiro