On 13.07.2015 16:24, Vaibhav Hiremath wrote: > > > On Saturday 11 July 2015 12:41 PM, Krzysztof Kozlowski wrote: >> W dniu 09.07.2015 o 20:47, Vaibhav Hiremath pisze: >>> 88PM800 family of device supports output of 32KHz clock (low jitter) >>> on CLK32K2/3 pin which can be supplied to other peripherals on the >>> board. >>> >>> This patch adds the devicetree binding to enable this feature. >>> >>> Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@xxxxxxxxxx> >>> --- >>> Documentation/devicetree/bindings/mfd/88pm800.txt | 6 ++++++ >>> 1 file changed, 6 insertions(+) >>> >>> diff --git a/Documentation/devicetree/bindings/mfd/88pm800.txt >>> b/Documentation/devicetree/bindings/mfd/88pm800.txt >>> index dec842f..ae1311c 100644 >>> --- a/Documentation/devicetree/bindings/mfd/88pm800.txt >>> +++ b/Documentation/devicetree/bindings/mfd/88pm800.txt >>> @@ -9,6 +9,12 @@ Required parent device properties: >>> - #interrupt-cells : should be 1. >>> The cell is the 88pm80x local IRQ number >>> >>> +Optional properties : >>> + - marvell,88pm800-32khz-xolj-out-en : If set, driver will enable >>> low jitter >>> + version of 32Khz clock output on >> >> I am not sure if I understand it correctly. The hardware always has such >> clocks and you only want to enable/disable it in DT? Any reasons why >> these should not be enabled always? >> > > Small amount of Power savings... > Although currently I do not have power numbers to justify this. > > As per spec, (it only talks about power consumption in power down state) > > Power-down State => VSYS > 2.8 => 4.5 μA > CLK32K2 = 0 => 18 μW This would be a power saving if it could be enabled/disabled runtime. But with DT you will either: 1. enable it always so there won't be any power saving, 2. disable it always so there won't be such clock. I can find a use case - when on some boards the clock output is not wired to anything so it cannot be used. In other cases (there is some potential user) this should be triggered per-use (runtime enabled/disabled). Do you have such case? I mean boards where this is not connected at all and boards where this is used? >> Enabling it in DT does not look like a job for DT. Maybe you there >> should be just a clock driver (clock provider)? >> > > It's init time (and one time) settings, wouldn't clock-provider > be overkill for this? The clock provider would be a proper way to do it and some PMICs I know do this. Examples are max77686 and s5m8767/s2mps11. These are PMICs used for Samsung SoCs. They have two or three 32kHz clocks. Best regards, Krzysztof -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
