Re: [PATCH 1/6] ARM: dts: dra7-evm: Make VDDA_1V8_PHY supply always on
From: Roger Quadros
Date: Wed Jul 02 2014 - 10:37:14 EST
On 07/02/2014 04:05 PM, Nishanth Menon wrote:
> On 07/02/2014 07:03 AM, Roger Quadros wrote:
>> After clarification from the hardware team it was found that
>> this 1.8V PHY supply can't be switched OFF when SoC is Active.
>> It can only be switched off when in PORz (power on reset).
>
> I dont think folks know the reasoning why hardware team decided that
> the voltage rail cannot be switched off -> I suggest adding the
> following information as well.
>
> Since isolation is not present in the design for these PHY IPs to
> allow for the PHY rail to be switched off, there is a very high risk
> of IP reliability and additional leakage paths which can result in
> additional power consumption.
>
> Only scenario where this rail can be switched off is part of Power on
> reset sequencing, but it needs to be kept always-on during operation.
This sort of information should be in the TRM instead, but doesn't harm to be in the commit message so I'll do that.
Thanks.
cheers,
-roger
>
>>
>> This patch is required for proper functionality of USB, SATA
>> and PCIe on DRA7-evm.
>>
>> CC: Rajendra Nayak <rnayak@xxxxxx>
>> CC: Tero Kristo <t-kristo@xxxxxx>
>> Signed-off-by: Roger Quadros <rogerq@xxxxxx>
>> ---
>> arch/arm/boot/dts/dra7-evm.dts | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/arm/boot/dts/dra7-evm.dts b/arch/arm/boot/dts/dra7-evm.dts
>> index 4adc280..8308954 100644
>> --- a/arch/arm/boot/dts/dra7-evm.dts
>> +++ b/arch/arm/boot/dts/dra7-evm.dts
>> @@ -240,6 +240,7 @@
>> regulator-name = "ldo3";
>> regulator-min-microvolt = <1800000>;
>> regulator-max-microvolt = <1800000>;
>> + regulator-always-on;
>> regulator-boot-on;
>> };
>>
>>
>
>
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