[PATCH 3.14 42/64] libata: Ignore spurious PHY event on LPM policy change

Greg Kroah-Hartman
2015-06-03T12:13:52Z

From: Gabriele Mazzotta <gabriele.mzt@gmail.com>

commit 09c5b4803a80a5451d950d6a539d2eb311dc0fb1 upstream.

When the LPM policy is set to ATA_LPM_MAX_POWER, the device might
generate a spurious PHY event that cuases errors on the link.
Ignore this event if it occured within 10s after the policy change.

The timeout was chosen observing that on a Dell XPS13 9333 these
spurious events can occur up to roughly 6s after the policy change.

Link: http://lkml.kernel.org/g/3352987.ugV1Ipy7Z5@xps13
Signed-off-by: Gabriele Mazzotta <gabriele.mzt@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/ata/libata-core.c | 15 ++++++++++++++-
drivers/ata/libata-eh.c | 3 +++
include/linux/libata.h | 9 +++++++++
3 files changed, 26 insertions(+), 1 deletion(-)

--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -6839,8 +6839,21 @@ u32 ata_wait_register(struct ata_port *a
*/
bool sata_lpm_ignore_phy_events(struct ata_link *link)
{
+ unsigned long lpm_timeout = link->last_lpm_change +
+ msecs_to_jiffies(ATA_TMOUT_SPURIOUS_PHY);
+
/* if LPM is enabled, PHYRDY doesn't mean anything */
- return !!(link->lpm_policy > ATA_LPM_MAX_POWER);
+ if (link->lpm_policy > ATA_LPM_MAX_POWER)
+ return true;
+
+ /* ignore the first PHY event after the LPM policy changed
+ * as it is might be spurious
+ */
+ if ((link->flags & ATA_LFLAG_CHANGED) &&
+ time_before(jiffies, lpm_timeout))
+ return true;
+
+ return false;
}
EXPORT_SYMBOL_GPL(sata_lpm_ignore_phy_events);

--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -3488,6 +3488,9 @@ static int ata_eh_set_lpm(struct ata_lin
}
}

+ link->last_lpm_change = jiffies;
+ link->flags |= ATA_LFLAG_CHANGED;
+
return 0;

fail:
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -204,6 +204,7 @@ enum {
ATA_LFLAG_SW_ACTIVITY = (1 << 7), /* keep activity stats */
ATA_LFLAG_NO_LPM = (1 << 8), /* disable LPM on this link */
ATA_LFLAG_RST_ONCE = (1 << 9), /* limit recovery to one reset */
+ ATA_LFLAG_CHANGED = (1 << 10), /* LPM state changed on this link */

/* struct ata_port flags */
ATA_FLAG_SLAVE_POSS = (1 << 0), /* host supports slave dev */
@@ -307,6 +308,12 @@ enum {
*/
ATA_TMOUT_PMP_SRST_WAIT = 5000,

+ /* When the LPM policy is set to ATA_LPM_MAX_POWER, there might
+ * be a spurious PHY event, so ignore the first PHY event that
+ * occurs within 10s after the policy change.
+ */
+ ATA_TMOUT_SPURIOUS_PHY = 10000,
+
/* ATA bus states */
BUS_UNKNOWN = 0,
BUS_DMA = 1,
@@ -785,6 +792,8 @@ struct ata_link {
struct ata_eh_context eh_context;

struct ata_device device[ATA_MAX_DEVICES];
+
+ unsigned long last_lpm_change; /* when last LPM change happened */
};
#define ATA_LINK_CLEAR_BEGIN offsetof(struct ata_link, active_tag)
#define ATA_LINK_CLEAR_END offsetof(struct ata_link, device[0])