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 <[email protected]> >> CC: Tero Kristo <[email protected]> >> Signed-off-by: Roger Quadros <[email protected]> >> --- >> 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; >> }; >> >> > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
