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Date: Mon, 2 Jun 2008 09:55:23 -0700
From: Kristen Carlson Accardi <kristen.c.accardi@...el.com>
To: Jeff Garzik <jeff@...zik.org>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>, Pavel Machek <pavel@....cz>,
Theodore Tso <tytso@....edu>, linux-ide@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ata: ahci: power off unused ports
On Mon, 02 Jun 2008 05:48:16 -0400
Jeff Garzik <jeff@...zik.org> wrote:
> Alan Cox wrote:
> >> The key requirement is per-port control. Ideally via hdparm or another
> >> userspace tool, but kernel command line (module options) or sysfs would
> >> be just fine too. And agreed, the minimal you need is simply 1/0 for
> >> the port's policy.
> >
> > We don't need it per port Jeff, you are being quite silly here. Right now
> > its permanently foo=0 for all ports and nobody has suffered anything too
> > horrible so being able to turn it off for all ports is clearly quite
> > sufficient for the neat future.
>
> Er, huh? foo=0 means hotplug continues to work on the unused ports.
> Nobody has suffered because we default to enabling all the goodies.
>
> Jeff
>
>
well - I disagree about nobody suffering. I would argue that most
users don't use hotplug and would prefer power savings to be the
default, but the patch I sent implemented a module parameter to allow
disable power savings if the user desires hotplug on every port.
Also keep in mind that this patch would still allow hotplug on a per
port basis if the BIOS tells us that this is either an external SATA
port or a port with some kind of externally accessible mechanism.
Here's the patch I sent so you can all review it again.
power off unused ports
If the port isn't either a drive bay or an external SATA port, do not
keep the phy powered on if the port is unoccupied. This saves .75 watts
on most laptops. A module parameter can be used to override this
behavior and allow the phy's to be powered up regardless of whether it
has externally accessible SATA ports.
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@...el.com>
---
drivers/ata/ahci.c | 21 +++++++++++++++++++++
drivers/ata/libata-core.c | 24 ++++++++++++++++++++++++
include/linux/libata.h | 1 +
3 files changed, 46 insertions(+)
Index: linux-ahci-phy/drivers/ata/ahci.c
===================================================================
--- linux-ahci-phy.orig/drivers/ata/ahci.c 2008-05-08 14:29:02.000000000 -0700
+++ linux-ahci-phy/drivers/ata/ahci.c 2008-05-08 14:31:05.000000000 -0700
@@ -53,9 +53,13 @@ static int ahci_skip_host_reset;
module_param_named(skip_host_reset, ahci_skip_host_reset, int, 0444);
MODULE_PARM_DESC(skip_host_reset, "skip global host reset (0=don't skip, 1=skip)");
+static int ahci_power_save = 1;
+module_param_named(power_save, ahci_power_save, int, 0444);
+MODULE_PARM_DESC(power_save, "Power off unused ports (0=don't power off, 1=power off)");
static int ahci_enable_alpm(struct ata_port *ap,
enum link_pm policy);
static void ahci_disable_alpm(struct ata_port *ap);
+static int ahci_is_hotplug_capable(struct ata_port *ap);
enum {
AHCI_PCI_BAR = 5,
@@ -166,6 +170,8 @@ enum {
PORT_CMD_ASP = (1 << 27), /* Aggressive Slumber/Partial */
PORT_CMD_ALPE = (1 << 26), /* Aggressive Link PM enable */
PORT_CMD_ATAPI = (1 << 24), /* Device is ATAPI */
+ PORT_CMD_ESP = (1 << 21), /* External SATA Port */
+ PORT_CMD_HPCP = (1 << 18), /* port is hot plug capable */
PORT_CMD_PMP = (1 << 17), /* PMP attached */
PORT_CMD_LIST_ON = (1 << 15), /* cmd list DMA engine running */
PORT_CMD_FIS_ON = (1 << 14), /* FIS DMA engine running */
@@ -1900,6 +1906,18 @@ static int ahci_pci_device_resume(struct
}
#endif
+static int ahci_is_hotplug_capable(struct ata_port *ap)
+{
+ void __iomem *port_mmio = ahci_port_base(ap);
+ u8 cmd;
+
+ if (!ahci_power_save)
+ return 1;
+
+ cmd = readl(port_mmio + PORT_CMD);
+ return ((cmd & PORT_CMD_HPCP) || (cmd & PORT_CMD_ESP));
+}
+
static int ahci_port_start(struct ata_port *ap)
{
struct device *dev = ap->host->dev;
@@ -1951,6 +1969,9 @@ static int ahci_port_start(struct ata_po
ap->private_data = pp;
+ /* set some flags based on port capabilities */
+ if (!ahci_is_hotplug_capable(ap))
+ ap->flags |= ATA_FLAG_NO_HOTPLUG;
/* engage engines, captain */
return ahci_port_resume(ap);
}
Index: linux-ahci-phy/drivers/ata/libata-core.c
===================================================================
--- linux-ahci-phy.orig/drivers/ata/libata-core.c 2008-05-08 14:28:57.000000000 -0700
+++ linux-ahci-phy/drivers/ata/libata-core.c 2008-05-08 14:29:50.000000000 -0700
@@ -162,6 +162,19 @@ MODULE_DESCRIPTION("Library module for A
MODULE_LICENSE("GPL");
MODULE_VERSION(DRV_VERSION);
+static void ata_phy_offline(struct ata_link *link)
+{
+ u32 scontrol;
+ int rc;
+
+ /* set DET to 4 */
+ rc = sata_scr_read(link, SCR_CONTROL, &scontrol);
+ if (rc)
+ return;
+ scontrol &= ~0xf;
+ scontrol |= (1 << 2);
+ sata_scr_write(link, SCR_CONTROL, scontrol);
+}
/**
* ata_force_cbl - force cable type according to libata.force
@@ -2671,6 +2684,7 @@ void ata_port_disable(struct ata_port *a
ap->link.device[0].class = ATA_DEV_NONE;
ap->link.device[1].class = ATA_DEV_NONE;
ap->flags |= ATA_FLAG_DISABLED;
+ ata_phy_offline(&ap->link);
}
/**
@@ -5609,6 +5623,8 @@ int ata_host_register(struct ata_host *h
if (ap->ops->error_handler) {
struct ata_eh_info *ehi = &ap->link.eh_info;
unsigned long flags;
+ int device_attached = 0;
+ struct ata_device *dev;
ata_port_probe(ap);
@@ -5627,6 +5643,14 @@ int ata_host_register(struct ata_host *h
/* wait for EH to finish */
ata_port_wait_eh(ap);
+ ata_link_for_each_dev(dev, &ap->link)
+ if (ata_dev_enabled(dev))
+ device_attached++;
+ if (!device_attached &&
+ (ap->flags & ATA_FLAG_NO_HOTPLUG)) {
+ /* no device present, disable port */
+ ata_port_disable(ap);
+ }
} else {
DPRINTK("ata%u: bus probe begin\n", ap->print_id);
rc = ata_bus_probe(ap);
Index: linux-ahci-phy/include/linux/libata.h
===================================================================
--- linux-ahci-phy.orig/include/linux/libata.h 2008-05-08 14:28:57.000000000 -0700
+++ linux-ahci-phy/include/linux/libata.h 2008-05-08 14:29:50.000000000 -0700
@@ -193,6 +193,7 @@ enum {
ATA_FLAG_AN = (1 << 18), /* controller supports AN */
ATA_FLAG_PMP = (1 << 19), /* controller supports PMP */
ATA_FLAG_IPM = (1 << 20), /* driver can handle IPM */
+ ATA_FLAG_NO_HOTPLUG = (1 << 21), /* port doesn't support HP */
/* The following flag belongs to ap->pflags but is kept in
* ap->flags because it's referenced in many LLDs and will be
--
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