On 11/15/2009 03:05 AM, Tejun Heo wrote:
11/14/2009 12:24 PM, Arjan van de Ven wrote:From f62ff8c98080b4a9e66f82f793145b863b4e183a Mon Sep 17 00:00:00 2001 From: Arjan van de Ven<arjan@xxxxxxxxxxxxxxx> Date: Fri, 13 Nov 2009 16:54:37 -0800 Subject: [PATCH] libata: Add ALPM power state accounting to the AHCI driver PowerTOP wants to show the user how effective the ALPM link power management is for the user. ALPM is worth around 0.5W on a quiet link; PowerTOP wants to be able to find and expose cases where the "quiet link" isn't actually quiet. This patch adds state accounting functionality to the AHCI driver for PowerTOP to use. The parts of the patch are 1) the sysfs logic of exposing the stats for each state in sysfs 2) the basic accounting logic that gets update on link change interrupts (or when the user accesses the info from sysfs) 3) a "accounting enable" flag; in order to get the accounting to work, the driver needs to get phyrdy interrupts on link status changes. Normally and currently this is disabled by the driver when ALPM is on (to reduce overhead); when PowerTOP is running this will need to be on to get usable statistics... hence the sysfs tunable. The PowerTOP output currently looks like this: Recent SATA AHCI link activity statistics Active Partial Slumber Device name 0.5% 99.5% 0.0% host0 (work to resolve "host0" to a more human readable name is in progress in PowerTOP)Most of logic seems to belong to libata generic part rather than in ahci itself. Wouldn't it be better to implement the thing as generic libata feature which ahci uses?
I had pretty much the same comment, on IRC. The accounting variables should probably live in struct ata_link, or a subsidiary (struct ata_link_accounting ?).
What little there is of driver-specific behavior can be handled from existing callbacks (->enable_pm) or by creating a driver-specific function that calls a generic function (eg. ahci_alpm_set_accounting could call ata_alpm_set_accounting, before twiddling AHCI's PORT_IRQ_MASK).
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