On 2016-12-13 12:04, Rob Herring wrote:
On Mon, Dec 12, 2016 at 04:54:20PM -0800, Subhash Jadavani wrote:
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).
Reviewed-by: Yaniv Gardi <ygardi@xxxxxxxxxxxxxx>
Signed-off-by: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx>
---
.../devicetree/bindings/ufs/ufshcd-pltfrm.txt | 10 ++++++
drivers/scsi/ufs/ufshcd-pltfrm.c | 14 ++++++++
drivers/scsi/ufs/ufshcd.c | 39
++++++++++++++++++++++
drivers/scsi/ufs/ufshcd.h | 4 +--
4 files changed, 65 insertions(+), 2 deletions(-)
diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
index a99ed55..c3836c5 100644
--- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
+++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
@@ -41,6 +41,14 @@ Optional properties:
-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.
+- 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.
This looks like you are putting policy for Linux into DT.
What I would expect to see here is disabling of states that don't work
due to some h/w limitation. Otherwise, it is a user decision for what
modes to go into. Also, I think link and device states should be
separate.
Yes, generally default level (3) is good enough (and recommended) for
all platforms and most likely user is only expected to change this if
they see issues (most H/W) on their platform or they want even more
aggressive power state (level-4 or level-5) and ready to take the
performance hit associated with resume latencies.
Also, I think it is better to keep Link and device states tied, one
reason is that we can't keep device in sleep/active state when Link is
in OFF state.
Rob
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