On Fri, Aug 10, 2018 at 4:50 PM Evan Green <evgreen@xxxxxxxxxxxx> wrote: > > UFS devices can be provisioned to have an initial power mode of either > active or sleep. If the initial power mode is sleep, then the host > controller driver must send a START STOP UNIT to the device in order > to wake it up. Unfortunately, the device will refuse to complete other > common low level operations, such as reading descriptors and attributes. > The Linux driver currently fails to enumerate devices that start in > sleep mode, because it fails to read the device descriptor from the > unconscious device. > > The way the UFS controller driver is structured, this presents a bit of > a Catch-22. In order to perform low-level enumeration of the device, the > driver needs to send a SCSI command. But SCSI needs low-level enumeration > of the device to be complete before full enumeration can occur. > > This change adds a method for sending low-level SCSI commands, modeled > after (and reusing much of) the mechanism for sending device management > commands. With this primitive, ufshcd_probe_hba can execute REQUEST SENSE > to clear the Unit Attention, and then a START STOP UNIT in order to bring > the device out of sleep mode. Only after this is done can the rest of > enumeration, such as reading the device descriptor and geometry descriptor, > be done. > > Signed-off-by: Evan Green <evgreen@xxxxxxxxxxxx> A very gentle bump, did anyone get a chance to take a look at this? Currently Linux can't enumerate UFS devices that start in Sleep mode.
