On 2/7/24 06:13, Niklas Cassel wrote: > 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. > > Signed-off-by: Niklas Cassel <cassel@xxxxxxxxxx> Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx> -- Damien Le Moal Western Digital Research
