On Sun, Jul 22, 2018 at 9:20 PM Asutosh Das (asd) <asutoshd@xxxxxxxxxxxxxx> wrote: > > On 7/12/2018 2:03 AM, Rob Herring wrote: > > On Fri, Jul 06, 2018 at 06:00:31PM +0530, Asutosh Das wrote: > >> From: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx> > >> > >> UFS device and link can be put in multiple different low power modes hence > >> UFS driver supports multiple different low power modes. By default UFS > >> driver selects the default (optimal) low power mode (which gives moderate > >> power savings and have relatively less enter and exit latencies) but > >> we might have to tune this default power mode for different chipset > >> platforms to meet the low power requirements/goals. Hence this patch > >> adds option to change default UFS low power mode (level). > >> > >> Signed-off-by: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx> > >> Signed-off-by: Venkat Gopalakrishnan <venkatg@xxxxxxxxxxxxxx> > >> Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx> > >> Signed-off-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx> > >> --- > >> .../devicetree/bindings/ufs/ufshcd-pltfrm.txt | 11 ++++++++ > >> drivers/scsi/ufs/ufshcd-pltfrm.c | 14 +++++++++++ > >> drivers/scsi/ufs/ufshcd.c | 29 +++++++++++++++------- > >> drivers/scsi/ufs/ufshcd.h | 4 +-- > >> 4 files changed, 47 insertions(+), 11 deletions(-) > >> > >> diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt > >> index c39dfef..f564d9a 100644 > >> --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt > >> +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt > >> @@ -38,6 +38,15 @@ Optional properties: > >> defined or a value in the array is "0" then it is assumed > >> that the frequency is set by the parent clock or a > >> fixed rate clock source. > >> +- rpm-level : UFS Runtime power management level. Following PM levels are supported: > >> + 0 - Both UFS device and Link in active state (Highest power consumption) > >> + 1 - UFS device in active state but Link in Hibern8 state > >> + 2 - UFS device in Sleep state but Link in active state > >> + 3 - UFS device in Sleep state and Link in hibern8 state (default PM level) > >> + 4 - UFS device in Power-down state and Link in Hibern8 state > >> + 5 - UFS device in Power-down state and Link in OFF state (Lowest power consumption) > >> +- spm-level : UFS System power management level. Allowed PM levels are same as rpm-level. > > > > What's the default? > > > > I assume these are minimums? The OS can pick higher power states. This > > seems to be a bit Linux specific (as 'runtime PM' could be considered > > Linux specific). For every other device, we don't put this type of > > information in DT, but is user controlled. > I didn't completely understand your comment. > Do you not want these properties to be in DT file? Right, not if it is a user decision. > When you say user-controlled, do you mean control it through sysfs entries? Yes. > > So really, wouldn't 1 > > property be sufficient for cases where a mode doesn't work due to > > some h/w limitation. Otherwise, it is an OS or user decision. > I didn't completely understand this. Could you please elaborate on your > intent here? The case that makes sense for this to be in DT is if there are h/w limitations that prevent some low power modes. In such a case, that limit is not likely specific to runtime PM or system suspend. > >> -lanes-per-direction : number of lanes available per direction - either 1 or 2. > >> Note that it is assume same number of lanes is used both > >> directions at once. If not specified, default is 2 lanes per direction. > >> @@ -66,4 +75,6 @@ Example: > >> freq-table-hz = <100000000 200000000>, <0 0>, <0 0>; > >> phys = <&ufsphy1>; > >> phy-names = "ufsphy"; > >> + rpm-level = <3>; > > > > Why specified if 3 is the default? > Ah yes - that should be removed. > I'll remove it in v2. > > > > >> + spm-level = <5>; > > > > These seem like sane defaults. When and why would you use some > > different? > I think each of the deeper sleep modes are associated with an increasing > wakeup latency. For e.g. '0' would have the highest power-consumption > and no resume latency at all as compared to '5'. > So depending on use-cases other modes may be chosen. The use-case can change in a running system. For example if you are plugged in, then you probably don't want to enter a lower power mode. Rob
