On 2016-12-19 10:38, Rob Herring wrote:
On Tue, Dec 13, 2016 at 2:16 PM, Subhash Jadavani
<subhashj@xxxxxxxxxxxxxx> wrote:
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.
What latencies can be tolerated is going to depend on the application
and could vary while running, so putting in DT doesn't make sense. I
would break down settings like this:
broken h/w -> DT
user tuning/config -> sysfs
sensible defaults -> driver
Make sense.
we already have #2 and #3 in place, will rework this patch so we have a
way to specify what is broken in h/w.
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.
The driver can tie the states to together if needed. Just document
what's broken in DT and let the driver make decisions.
Yes, agreed. will rework this patch so we have a way to specify what is
broken in h/w and separate the device and link states (something like
broken-hibern8, broken-sleep etc.)
Thanks for the suggestions.
Rob
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