On 6/30/25 08:26, Damien Le Moal wrote:
In ata_eh_revalidate_and_attach(), a link LPM policy is always set to ATA_LPM_MAX_POWER before calling ata_dev_revalidate() to ensure that the call to ata_phys_link_offline() does not return true, thus causing an unnecessary device reset. This change was introduced with commit 71d7b6e51ad3 ("ata: libata-eh: avoid needless hard reset when revalidating link"). However, setting the link LPM policy to ATA_LPM_MAX_POWER may be visible only after some time, depending on the power state the link was in. E.g. transitioning out of the Partial state should take no longer than a few microseconds, but transitioning out of the Slumber or DevSleep state may take several milliseconds. So despite the changes introduced with commit 71d7b6e51ad3 ("ata: libata-eh: avoid needless hard reset when revalidating link"), we can still endup with ata_phys_link_offline() seeing a link SCR_STATUS register signaling that the device is present (DET is equal to 1h) but that the link PHY is still in a low power mode (e.g. IPM is 2h, signaling "Interface in Partial power management state"). In such cases, ata_phys_link_offline() returns true, causing an EIO return for ata_eh_revalidate_and_attach() and a device reset. Avoid such unnecessary device resets by introducing a relaxed version of the link offline test implemented by ata_phys_link_offline() with the new helper function ata_eh_link_established(). This functions returns true if for the link SCR_STATUS register we see that: - A device is still present, that is, the DET field is 1h (Device presence detected but Phy communication not established) or 3h (Device presence detected and Phy communication established). - Communication is established, that is, the IPM field is not 0h, indicating that the PHY is online or in a low power state. Signed-off-by: Damien Le Moal <dlemoal@xxxxxxxxxx> --- drivers/ata/libata-eh.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c index f98d5123e1e4..7f5d13f9ca73 100644 --- a/drivers/ata/libata-eh.c +++ b/drivers/ata/libata-eh.c @@ -2071,6 +2071,33 @@ static void ata_eh_get_success_sense(struct ata_link *link) ata_eh_done(link, dev, ATA_EH_GET_SUCCESS_SENSE); }+/*+ * Check if a link is established. This is a relaxed version of + * ata_phys_link_online() which accounts for the fact that this is potentially + * called after changing the link power management policy, which may not be + * reflected immediately in the SSTAUS register (e.g., we may still be seeing + * the PHY in partial, slumber or devsleep Partial power management state. + * So check that: + * - A device is still present, that is, DET is 1h (Device presence detected + * but Phy communication not established) or 3h (Device presence detected and + * Phy communication established) + * - Communication is established, that is, IPM is not 0h, indicating that PHY + * is online or in a low power state. + */ +static bool ata_eh_link_established(struct ata_link *link) +{ + u32 sstatus; + u8 det, ipm; + + if (sata_scr_read(link, SCR_STATUS, &sstatus)) + return false; + + det = sstatus & 0x0f; + ipm = (sstatus >> 8) & 0x0f; + + return (det & 0x01) && ipm; +} + /** * ata_eh_link_set_lpm - configure SATA interface power management * @link: link to configure @@ -3275,7 +3302,7 @@ static int ata_eh_revalidate_and_attach(struct ata_link *link, goto err; }- if (ata_phys_link_offline(ata_dev_phys_link(dev))) {+ if (!ata_eh_link_established(ata_dev_phys_link(dev))) { rc = -EIO; goto err; }
Makes me wonder: if the phy is taking some time, don't we need to wait at some point for the transition to complete? From a cursory glance we just continue, and (apparently) hope that everything will be well eventually. Hmm? Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@xxxxxxx +49 911 74053 688 SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich
