rge: make int_rx_mod a sysctl tunable

[chris.longros_gmail.com]

Summary

The interrupt moderation timer value was hardcoded to 0x2600. Add a
per-interface sysctl dev.rge.%d.int_rx_mod tunable so users can
adjust this value at runtime.

Signed-off-by: Christos Longros <[e-mail]>

[chris.longros_gmail.com]

@adrian could you please review the commit when you have time? Thanks :)

[adrian]

can you add some validation of the parameter before programming it into the register? surely it's not a single 32 bit field?

[adrian]

I've pushed D56103; please rebase this on top of -HEAD as of today and please address limiting the rx moderation value appropriately (just do it when you program; don't bother going through creating a SYSCTL_PROC hook to validate it on read/write..)

[chris.longros_gmail.com]

In D56102#1291882, @adrian wrote:

can you add some validation of the parameter before programming it into the register? surely it's not a single 32 bit field?

Added validation in rge_setup_sim_im() to clamp negative values before programming the register. I probed TIMERINT0 on hardware via PCI BAR0: writing 0xFFFFFFFF reads back 0xFFFFFFFF, so the register stores 32 bits. Could you confirm the timer field width so I can add an upper bound if needed?