libata: reimplement link power management

The current LPM implementation has the following issues.

* Operation order isn't well thought-out.  e.g. HIPM should be
  configured after IPM in SControl is properly configured.  Not the
  other way around.

* Suspend/resume paths call ata_lpm_enable/disable() which must only
  be called from EH context directly.  Also, ata_lpm_enable/disable()
  were called whether LPM was in use or not.

* Implementation is per-port when it should be per-link.  As a result,
  it can't be used for controllers with slave links or PMP.

* LPM state isn't managed consistently.  After a link reset for
  whatever reason including suspend/resume the actual LPM state would
  be reset leaving ap->lpm_policy inconsistent.

* Generic/driver-specific logic boundary isn't clear.  Currently,
  libahci has to mangle stuff which libata EH proper should be
  handling.  This makes the implementation unnecessarily complex and
  fragile.

* Tied to ALPM.  Doesn't consider DIPM only cases and doesn't check
  whether the device allows HIPM.

* Error handling isn't implemented.

Given the extent of mismatch with the rest of libata, I don't think
trying to fix it piecewise makes much sense.  This patch reimplements
LPM support.

* The new implementation is per-link.  The target policy is still
  port-wide (ap->target_lpm_policy) but all the mechanisms and states
  are per-link and integrate well with the rest of link abstraction
  and can work with slave and PMP links.

* Core EH has proper control of LPM state.  LPM state is reconfigured
  when and only when reconfiguration is necessary.  It makes sure that
  LPM state is reset when probing for new device on the link.
  Controller agnostic logic is now implemented in libata EH proper and
  driver implementation only has to deal with controller specifics.

* Proper error handling.  LPM config failure is attributed to the
  device on the link and LPM is disabled for the link if it fails
  repeatedly.

* ops->enable/disable_pm() are replaced with single ops->set_lpm()
  which takes @policy and @hints.  This simplifies driver specific
  implementation.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 11 insertions, 6 deletions

diff --git a/include/linux/libata.h b/include/linux/libata.h
index 7770eeb21039..bc4ee218b185 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -172,6 +172,7 @@ enum {
         ATA_LFLAG_NO_RETRY      = (1 << 5), /* don't retry this link */
         ATA_LFLAG_DISABLED      = (1 << 6), /* link is disabled */
         ATA_LFLAG_SW_ACTIVITY   = (1 << 7), /* keep activity stats */
+        ATA_LFLAG_NO_LPM        = (1 << 8), /* disable LPM on this link */
 
         /* struct ata_port flags */
         ATA_FLAG_SLAVE_POSS     = (1 << 0), /* host supports slave dev */
@@ -324,12 +325,11 @@ enum {
         ATA_EH_HARDRESET        = (1 << 2), /* meaningful only in ->prereset */
         ATA_EH_RESET            = ATA_EH_SOFTRESET | ATA_EH_HARDRESET,
         ATA_EH_ENABLE_LINK      = (1 << 3),
-        ATA_EH_LPM              = (1 << 4),  /* link power management action */
         ATA_EH_PARK             = (1 << 5), /* unload heads and stop I/O */
 
         ATA_EH_PERDEV_MASK      = ATA_EH_REVALIDATE | ATA_EH_PARK,
         ATA_EH_ALL_ACTIONS      = ATA_EH_REVALIDATE | ATA_EH_RESET |
-                                  ATA_EH_ENABLE_LINK | ATA_EH_LPM,
+                                  ATA_EH_ENABLE_LINK,
 
         /* ata_eh_info->flags */
         ATA_EHI_HOTPLUGGED      = (1 << 0),  /* could have been hotplugged */
@@ -377,7 +377,6 @@ enum {
         ATA_HORKAGE_BROKEN_HPA  = (1 << 4),     /* Broken HPA */
         ATA_HORKAGE_DISABLE     = (1 << 5),     /* Disable it */
         ATA_HORKAGE_HPA_SIZE    = (1 << 6),     /* native size off by one */
-        ATA_HORKAGE_LPM         = (1 << 7),     /* Link PM problems */
         ATA_HORKAGE_IVB         = (1 << 8),     /* cbl det validity bit bugs */
         ATA_HORKAGE_STUCK_ERR   = (1 << 9),     /* stuck ERR on next PACKET */
         ATA_HORKAGE_BRIDGE_OK   = (1 << 10),    /* no bridge limits */
@@ -475,6 +474,11 @@ enum ata_lpm_policy {
         ATA_LPM_MIN_POWER,
 };
 
+enum ata_lpm_hints {
+        ATA_LPM_EMPTY           = (1 << 0), /* port empty/probing */
+        ATA_LPM_HIPM            = (1 << 1), /* may use HIPM */
+};
+
 /* forward declarations */
 struct scsi_device;
 struct ata_port_operations;
@@ -702,6 +706,7 @@ struct ata_link {
         unsigned int            hw_sata_spd_limit;
         unsigned int            sata_spd_limit;
         unsigned int            sata_spd;       /* current SATA PHY speed */
+        enum ata_lpm_policy     lpm_policy;
 
         /* record runtime error info, protected by host_set lock */
         struct ata_eh_info      eh_info;
@@ -773,7 +778,7 @@ struct ata_port {
 
         pm_message_t            pm_mesg;
         int                     *pm_result;
-        enum ata_lpm_policy     lpm_policy;
+        enum ata_lpm_policy     target_lpm_policy;
 
         struct timer_list       fastdrain_timer;
         unsigned long           fastdrain_cnt;
@@ -839,8 +844,8 @@ struct ata_port_operations {
         int  (*scr_write)(struct ata_link *link, unsigned int sc_reg, u32 val);
         void (*pmp_attach)(struct ata_port *ap);
         void (*pmp_detach)(struct ata_port *ap);
-        int  (*enable_pm)(struct ata_port *ap, enum ata_lpm_policy policy);
-        void (*disable_pm)(struct ata_port *ap);
+        int  (*set_lpm)(struct ata_link *link, enum ata_lpm_policy policy,
+                        unsigned hints);
 
         /*
          * Start, stop, suspend and resume