Re: ahci power management
Matthew Dillon <dillon@apollo.backplane.com> wrote:
>
> If you set up a SYSCTL_PROC (you can probably find examples
> in various places in the kernel) then whenever the sysctl is
> read or written the procedure callback is made.
>
> In order to safely modify the feature while AHCI is operational
> you probably just need to get the AHCI port lock. There are
> numerous examples in the ahci code of calls to e.g.
> ahci_os_lock_port(ap). So you'd get the lock, modify the
> feature, and then release the lock.
>
> The patch looks pretty good, but needs one or two more passes
> before comitting. There are capability bits for AHCI features
> and the power management feature must be conditionalized on the
> capability existing. I think the one that applies is
> AHCI_REG_CAP_SALP. See other AHCI_REG_CAP_* uses in the ahci
> code for examples.
>
I have updated the patch at
http://leaf.dragonflybsd.org/~hofmann/ahci_pwrmgmt.patch
accordingly.
Link power management can now be switched on and off with a sysctl.
On my system it is "hw.ahci0.0.link_pwr_mgmt"
(0 = disabled, 1 = medium, 2 = aggressive).
Thanks for the help on the ML and on irc,
Johannes
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