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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 commit71d7b6e51a("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 commit71d7b6e51a("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@kernel.org> Reviewed-by: Niklas Cassel <cassel@kernel.org> Reviewed-by: Hannes Reinecke <hare@suse.de> Link: https://lore.kernel.org/r/20250701125321.69496-5-dlemoal@kernel.org Signed-off-by: Niklas Cassel <cassel@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.