Linux/AM3352: Changing pinmux mode

Angel Falcon

Expert 1160 points

Part Number: AM3352

Tool/software: Linux

Hello,

We have our own board design based on am3352 processor and we use kernel 4.4.19 from TI SDK 03.01.00.06.

In our .dts we configure mcasp1 interface pins

         0x1a0 ( PIN_OUTPUT | MUX_MODE3 ) /* (B12) mcasp0_aclkr.mcasp1_aclkx */
         0x1a4 ( PIN_OUTPUT | MUX_MODE3 ) /* (C13) mcasp0_fsr.mcasp1_fsx */
         0x1ac ( PIN_OUTPUT | MUX_MODE3 ) /* (A14) mcasp0_ahclkx.mcasp1_axr1 TX */
         0x1a8 ( PIN_INPUT | MUX_MODE3 ) /* (D13) mcasp0_axr1.mcasp1_axr0 RX */

But, some times we need to change these pin modes, set them as inputs, make some work and then change them again to MUX_MODE3.

We want to do this inside kernel space, in one of the drivers we are writting, but I do not find functions to change pinmux mode.

Could you help us to find how to do this?

Best regards

over 8 years ago

0 Biser Gatchev-XID over 8 years ago

TI__Guru**** 393215 points

Hi,

You can write directly to the pinmux registers in kernel code.

However you should note that changing pinmux at runtime is not recommended by TI, due to the configuration of IO sets and delay on many of the pins. There is a possibility of glitches occurring on pins if this is done during runtime operation.

0 Angel Falcon over 8 years ago in reply to Biser Gatchev-XID

Expert 1160 points

Hi,

Thank you for your help.
I wanted to avoid writing directly to registers, but that seems to be the solution.
You are right, application must take extra care when trying to change pin mode.
Best regards

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Linux/AM3352: Changing pinmux mode