Hello there, This adds a module parameter 'external_port_map' to the 'ahci' driver. Normally we do not enable LPM on ports that are marked as external by firmware. However, as always, firmware can have bugs and can have forgotten to mark a port as external. This module parameter gives those users a way to still have their ports hotplug capable, without modifying the 'mobile_lpm_policy', which will affect the LPM policy for all ports. This module parameter allows you to just mark a single port as external, such that you will still get power saving on the ports that are not marked as external. One example where this module parameter can also be used, is for buggy devices such as the "HL-DT-ST BD-RE BU40N" Blu-Ray player, which does not reply to a regular COMRESET (the controller sees nothing as connected), instead it will send a hotplug event when, and only when the user presses the tray open button. Not replying to a COMRESET is not spec compliant. If a port does not detect any device on a port, and LPM is enabled on that port, and the port is not marked as hotplug capable, then there should be no way that a device can be hotplugged later, so libata powers off the port/PHY to save power. This module parameter will give users a way to handles such non spec compliant devices in a more fine grained way (rather than using the big 'mobile_lpm_policy' hammer). There does also exist a per port link_power_management_policy sysfs attribute, however, for many people, a kernel module is more convenient compared to writing udev rules. Kind regards, Niklas Niklas Cassel (2): ata: ahci: Create a ahci_get_port_map_helper() helper ata: ahci: Add external_port_map module parameter drivers/ata/ahci.c | 89 +++++++++++++++++++++++++++++++++++++--------- 1 file changed, 72 insertions(+), 17 deletions(-) -- 2.48.0
