rs_timer

[Todd Poynor]

Prakash kanthi wrote:
> Hi Folks,
>
> I observed that, even after linux boots and INIT
> process starts, rs_timer stays active and causes the
> rs_interrupt_single to be called.

Depending on your board and the kernel version you're using, this might
be the result of using IRQ 0 for ttyS0 interrupts (as occurs for ppc_405
boards).  The stock kernel from kernel.org does not recognize IRQ 0 as a
valid value, and sets up rs_timer polling instead.  Recent
linuxppc_2_4_devel kernels (and perhaps other ppc kernel trees) are
modified to remove this restriction; see modifications to
drivers/char/serial.c that remove checks for "irq != 0" and such.
MontaVista Linux makes this an optional feature, enabled by defining
SERIAL_IRQ0_VALID.


--
Todd


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