3-wire spi not supported ?

ranchu

Guru 20755 points

Hello,

I use 3-wire spi device with omap35x.

But it seems not to be detected from kernbel code.

I suspect it is issue of 3-wire not supported in kernel driver ?

Is is correct assumption ? Is there any patch to support 3-wire with omap ?

Regards,

Ran

over 9 years ago

0 Titusrathinaraj Stalin over 9 years ago

TI__Guru** 116100 points

Have you enabled the SPI support in board file and checked the probe function in SPI driver ?

0 ranchu over 9 years ago in reply to Titusrathinaraj Stalin

Guru 20755 points

Hi Titus,

Yes, I did.
We struggle with this, but the suspicsion is that TI's driver omap2_mcspi.c, just does not support 3-wire devices,
therefore it will not help becuase the device supports only 3-wire.
I just wanted to verify that this is the state , and there are no patches from TI for 3-wire spi.

Regards,
Ran

0 Titusrathinaraj Stalin over 9 years ago in reply to ranchu

TI__Guru** 116100 points

Did you mean 3-wire SPI is "SIMO, SMIO and CLK" and without EN pin ?

0 ranchu over 9 years ago in reply to Titusrathinaraj Stalin

Guru 20755 points

Hi,

"The 3-wire communication mode operates similar to SPI mode. However, in the 3-wire mode,
there is one bi-directional I/O instead of separate data in and data out signals. The 3-wire interface consists of the MCS,
MDIO and MCL. The 3-Wire Master interface reads data on the falling edge of MCL. During 3-Wire write operation the 3-
Wire master outputs the data on the falling edge of MCL"

Regards,
Ran

0 Titusrathinaraj Stalin over 9 years ago in reply to ranchu

TI__Guru** 116100 points

Dear Ran,
Yes, it seems the driver is not supporting the 3-wire SPI (half duplex)
Can you try to use the existing driver with tie up the SIMO & SOMI of host to 10K resistor as given in below link ?
But I'm not sure about this.

In newer kernel, the have added the support as a property "spi-3wire" , it may come in future for newer devices.

http://lxr.free-electrons.com/source/Documentation/devicetree/bindings/spi/spi-bus.txt?v=3.8

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3-wire spi not supported ?