topic IMX6Q SPI Speed in i.MX Processors

IMX6Q SPI Speed

brli — Thu, 18 Jul 2019 03:34:57 GMT

Hi,

Could you suggest how to improve SPI speed?

We are connecting LCD(320x240) device to IMX6Q SPI interface, but its data transfer speed is slow. detail as attached

Free for 9.5 us per 8 bytes during transferring 320*240*2 bytes data size.

Free for 245 ns per 8 bits during transferring 320*240*2 bytes data size.

How can i reduce these free time?

Thanks!

Br Li

Re: IMX6Q SPI Speed

igorpadykov — Thu, 18 Jul 2019 08:34:25 GMT

Hi br

max. ecspi frequency can be found in sect.4.12.2.1 ECSPI Master Mode Timing

i.MX 6Dual/6Quad Applications Processors for Consumer Products - Data Sheet

So in software one can try to set its clock to max. available values and use

bursts configured by BURST_LENGTH field ECSPIx_CONREG register.

Best regards
igor
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Re: IMX6Q SPI Speed

brli — Mon, 29 Jul 2019 09:49:36 GMT

Hi Igorpadykov,

Where can i set the BURST_LENGTH in Linux source code?

Thanks!

Br Li

Re: IMX6Q SPI Speed

igorpadykov — Mon, 29 Jul 2019 15:04:18 GMT

one can look at ecspi driver

spi-imx.c\spi\drivers - linux-imx - i.MX Linux kernel

Best regards
igor

Re: IMX6Q SPI Speed

brli — Tue, 30 Jul 2019 03:16:38 GMT

Hi Igorpadykov,

Modify the burst length can reduce the the 245ns free time per 8 bits,but my LCD device protocol specified is 8 bits transfer. otherwise it works abnormal.

Can we possible to reduce the 9.5 us free time per 8 bytes, or increase the 8 bytes to 16/24/32 bytes?

Thanks!

Br Li

Re: IMX6Q SPI Speed

angelo_d — Thu, 17 Dec 2020 22:20:59 GMT

Note that there are different speed limit if you only write on TX fifo or only read from RX,
at least so it seems (IMX6DQIEC.pdf 4.12.2.1)

RX max speed seems 25Mhz for fast pad group, 18Mhz for slow group.

While for TX seems possible to reach 66Mhz.

Is this assumption correct ?