scsi: ufs: Fix WriteBooster flush during runtime suspend
Currently UFS host driver promises VCC supply if UFS device needs to do WriteBooster flush during runtime suspend. However the UFS specification mentions: "While the flushing operation is in progress, the device is in Active power mode." Therefore UFS host driver needs to promise more: Keep UFS device as "Active power mode", otherwise UFS device shall not do any flush if device enters Sleep or PowerDown power mode. Similarly, the same promises shall be applied if device needs urgent BKOP during runtime suspend. Fix this by not changing device power mode if WriteBooster flush or urgent BKOP is required in ufshcd_suspend(). Now, if device finishes its job but is not resumed for a very long time, system will have unnecessary power drain because VCC is still supplied. A method to re-check the threshold of keeping VCC supply is required to fix the power drain. However, the threshold re-check needs to re-activate the link first because the decision depends on the latest device status. Also introduce a delayed work to force runtime resume after a certain delay during runtime suspend. This makes threshold re-check happen natually in the entry of the next runtime-suspend. The device can continue its WriteBooster flush or urgent BKOP jobs soon after resumed if device has no upcoming requests and link enters hibern8 state either by Auto-Hibern8 or hibern8 during clk-gating scheme. This solution not only prevents power drain but also makes as much use of time as possible for device's background jobs. Link: https://lore.kernel.org/r/20200522083212.4008-5-stanley.chu@mediatek.com Reviewed-by:Asutosh Das <asutoshd@codeaurora.org> Signed-off-by: