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AHCI 1.3.3, 7.3.1.1 Software Flow for Hot Plug Removal Detection states: "To reliably detect hot plug removals, software must disable interface power management. Software should perform the following initialization on a port after a device is attached: -Set PxSCTL.IPM to 3h to disable interface power management state transitions. -Set PxCMD.ALPE to ‘0’ to disable aggressive power management. -Ensure PxIE.PRCE is set to ‘1’ to enable interrupts on hot plug removals. -Disable device initiated interface power management by issuing the appropriate SET FEATURES command." Further, AHCI 1.3.3, 7.3 Native Hot Plug Support states: "The HBA shall set the PxSERR.DIAG.X bit to ‘1’ when a COMINIT is received from the device. Hot plug insertions are detected via the PxIS.PCS bit that directly reflects the PxSERR.DIAG.X bit. The HBA shall set the PxSERR.DIAG.N bit to ‘1’ when the HBA’s internal PhyRdy signal changes state. Hot plug removals are detected via the PxIS.PRCS bit that directly reflects the PxSERR.DIAG.N bit. Note that PxSERR.DIAG.N is also set to ‘1’ on insertions and during interface power management entry/exit." ahci_set_lpm() already disables the PxIS.PRCS interrupt if setting a LPM policy != ATA_LPM_MAX_POWER, so we cannot detect hot plug removals when LPM policy != ATA_LPM_MAX_POWER. We do have PxIS.PCS interrupt enabled even for LPM policy != ATA_LPM_MAX_POWER, so we should theoretically still be able to detect hot plug insertions even when LPM is enabled. However, in practise, for LPM policy ATA_LPM_MED_POWER_WITH_DIPM, ATA_LPM_MIN_POWER_WITH_PARTIAL, and ATA_LPM_MIN_POWER, if there is no link enabled, sata_link_scr_lpm() will set SControl.DET = 0x4, which will transition the port to the "P:Offline" state. The P:Offline mode is described in SATA Gold 3.5a: 4.1.1.103 Phy offline: "In this mode the host Phy is forced off and the host Phy does not recognize nor respond to COMINIT or COMWAKE. This mode is entered by setting the DET field of the SControl register to 0100b. This is a mechanism for the host to turn off its Phy." So in the P:Offline state the PHY does not recognize the unsolicited COMINIT which is sent on a hot plug insertion. While we could change sata_link_scr_lpm() to never power off an external port for LPM policy != ATA_LPM_MAX_POWER (in order be able to handle hot plug insertions), we still would not be able to handle hot plug removals. Thus, simply modify ahci_update_initial_lpm_policy() to not enable LPM if the port advertises itself as an external port, as this function is already being used to set/override the initial LPM policy. Tested-by: Damien Le Moal <dlemoal@kernel.org> Tested-by: Jian-Hong Pan <jhp@endlessos.org> Reviewed-by: Damien Le Moal <dlemoal@kernel.org> Reviewed-by: Mario Limonciello <mario.limonciello@amd.com> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Niklas Cassel <cassel@kernel.org> |
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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 Restructured Text 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.