3-wire spi not supported ?

ranchu

Guru 20755 points

Hi,

I'm using PSP 4.1.0.2 .

I've tried to configure the driver to 3-wire but on doing that the driver fails with the following:

spi spi3.0: setup: unsupported mode bits 10
omap2_mcspi omap2_mcspi.3: can't setup spi3.0, status -22
omap2_mcspi omap2_mcspi.3: can't create new device for elbit_lcd

Is there a way to work with spi 3-wire with dm8148 ?

Best Regards,

Ran

over 9 years ago

0 Pavel Botev over 9 years ago

TI__Guru**** 170625 points

Ran,

What do you mean by "3-wire spi"? Do you mean you need to use only 3 pins of the SPI? If yes, which pins exactly?

BR
Pavel

0 ranchu over 9 years ago in reply to Pavel Botev

Guru 20755 points

Hi Pavel,

3-wire SPI means that SDI and SDO are connected together.
in /include/linux/spi/spi.h you can find:
#define SPI_3WIRE 0x10
trying to use it with DM8148 PSP 4.1.0.2 result in the errors I've posted before.
I try to understand if this is a HW limitation or driver in PSP limitation.

Best Regards,
Ran

0 Pavel Botev over 9 years ago in reply to ranchu

TI__Guru**** 170625 points

Ran,

See if the below pointers will help:

e2e.ti.com/.../315070
e2e.ti.com/.../382636
e2e.ti.com/.../168346

processors.wiki.ti.com/.../Linux_Core_SPI_User's_Guide

linux-kernel/drivers/spi/spi.c
linux-kernel/drivers/spi/spidev.c

linux-kernel/Documentation/spi/spidev_test.c
linux-kernel/Documentation/spi/spidev

BR
Pavel

0 ranchu over 9 years ago in reply to Pavel Botev

Guru 20755 points

Hi Pavel,

Thank you for the links.

I actually made e2e search before posting the question, and found those posts, but none of them give answer to the question about 3-wire spi support with DM8148 (or omap devices).

The 3-wire support is very important for me becuase it is the only way I can verify that the writing to the spi device worked. Without it we can't validate the writing.

The driver gives an error, but I am not sure if it is a limitation of HW or driver SW ?

If it is a HW limitation, than there is nothing we can do, but in case it is a driver limitation, maybe there is a solution or patch in oreder to work with 3-wire device ?

Regards,

Ran

0 Pavel Botev over 9 years ago in reply to ranchu

TI__Guru**** 170625 points

You can check DM814x documentation (datasheet, TRM, silicon errata) to check for SPI HW support.

BR
Pavel

0 ranchu over 9 years ago in reply to Pavel Botev

Guru 20755 points

Hi Pavel,

Did you ever tried to use 3-wire devices with omap (in linux) ?

Thanks,
Ran

0 Pavel Botev over 9 years ago in reply to ranchu

TI__Guru**** 170625 points

Ran,

No I did not. I have DM814x TI EVM, where the two data pins are used.

From HW point of view, single data pin mode is supported, when you have receive only slave or transmit only slave. See DM814x TRM, sections:
22.2.2 SPI Transmission
22.2.2.2 Single Data Pin Interface Mode
22.2.2.2.1 Example With a Receive-Only Slave
22.2.2.2.2 Example With a Transmit-Only Slave

Regards,
Pavel

0 ranchu over 8 years ago in reply to Pavel Botev

Guru 20755 points

Hi Pavel,

If I can may ask on this subject:

Is there any idea or reference how to add support for 3WIRES in linux ?

Regards,
Ran

0 Pavel Botev over 8 years ago in reply to ranchu

TI__Guru**** 170625 points

Ran,

I search for example regarding SPI_3WIRE but I am not able to find.

The reference should be the DM814x TRM. You can add SPI_3WIRE support in the SPI driver (omap2_mcspi.c), just follow TRM instructions.

Regards,
Pavel

0 ranchu over 8 years ago in reply to Pavel Botev

Guru 20755 points

OK Pavel,

Thanks!

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3-wire spi not supported ?