AM335x switch pin's function

user4121072

Hi All,

I am working on AM335x, and now I was confused by the pin's function switch, describe as below:

As you know the functions of pin were defined at arch/arm/mach-omap2/. but now I want to define a pin as GPIO when system bootup, and than change the pin as uart function.

For example, driver A will be "insmod" after system bootup, this driver use the uart0_rtsn as GPIO output, and then, driver A will be "remod", Driver B will be "insmod", this driver use the uart0_rtsn as uart4_txd.

In other words, the functions(GPIO and uart_txd) of uart0_rtsn was defined in different driver at different time, is it possible?

Thanks in advance,

Jakebo

over 9 years ago

0 Biser Gatchev-XID over 9 years ago

TI__Guru**** 393215 points

Hi,

I will forward this to the software team.

0 Kemal R. Shakir over 9 years ago in reply to Biser Gatchev-XID

TI__Guru 55345 points

Hello Jakebo,

Yes, it is possible. Please, search for a Runtime pinmuxing within the Kernel documentation.

Best regards,
Kemal

0 Biser Gatchev-XID over 9 years ago in reply to Kemal R. Shakir

TI__Guru**** 393215 points

An important note from hardware point of view: You should be aware that the state of the pin is undefined for a few ns when changed from one mux mode to another. This occurs because delay paths through the pin-mux selection logic may temporarily select an unexpected peripheral as the decode logic resolves the new source of output and output enable. This is very important to consider if changing the mux mode on a terminal that connects to an important function like chip select because the output could glitch. It is also best if you never do this on a terminal that is being used as an input. A terminal being used as an input is most like connected to an output of an external device. The two outputs could be in contention for a few ns if the output enable is turned on during the mux mode change.