Linux/AM3359: GPMC communication with an external FPGA with two Chip Selects

Mobin P K

Expert 1035 points

Part Number: AM3359

Tool/software: Linux

Hello,

Please clarify the following doubts regarding GPMC communication with an external FPGA.

16 bit GPMC asynchronous mode is interfaced with FPGA using CS3 for normal data transfer & CS5 for DMA operation

1) If am transmitting 256kbytes over CS5 and at the same time I am operating CS3 for single write/read. How would be the behavior of GPMC. whether it will stop the DMA operation and start CS3 single write / read or immediately stop the DMA operation over CS5 ?

2) If am using 3 Chip selects. How would be the priority of data transfer operation over these chip selects ?

Waiting for your reply

thanks

Mobin P K

over 6 years ago

0 Krunal Bhargav34 over 6 years ago

TI__Mastermind 44955 points

Hello Mobin,

I have reached out to our GPMC experts and I will keep you posted on any updates.

Regards,
Krunal

0 Krunal Bhargav34 over 6 years ago in reply to Krunal Bhargav34

TI__Mastermind 44955 points

Hi Mobin,

I am still looking into your first question but for the second question, there is no such arbitration/prioritization inside the GPMC on a chip select basis. This all occurs higher up the chain inside the L3 interconnect.

Regards,
Krunal

0 Krunal Bhargav34 over 6 years ago in reply to Krunal Bhargav34

TI__Mastermind 44955 points

Hi Mobin,

Based on my discussion with our experts, DMA vs CPU arbitration is happening outside GPMC at the L3 interconnect. Please refer to the "L3 Interconnect" section in the AM335x Technical Reference Manual.

Regards,
Krunal

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Linux/AM3359: GPMC communication with an external FPGA with two Chip Selects