| Message ID | 1436442431-3471-4-git-send-email-vaibhav.hiremath@linaro.org |
|---|---|
| State | New |
| Headers | show |
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@linaro.org> >> --- >> 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 > 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? Thanks, Vaibhav -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
On Monday 13 July 2015 01:01 PM, Krzysztof Kozlowski wrote: > 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@linaro.org> >>>> --- >>>> 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). > Exactly, > Do you have such case? I mean boards where this is not connected at all > and boards where this is used? > The PXA1928 based board which I have, CLK32K1 (G3 pad) = Used by Wireless chip CLK32K2 (G11 pad) = Not connected to anything, so we need to disable this output >>> 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. > This is good to know. Let me take a look at these drivers. Thanks, Vaibhav -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 + CLK32K3 - for 88pm800 + CLK32K2 - for 88pm860 + 88pm80x family of devices consists of varied group of sub-devices: Device Supply Names Description
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@linaro.org> --- Documentation/devicetree/bindings/mfd/88pm800.txt | 6 ++++++ 1 file changed, 6 insertions(+)