From mboxrd@z Thu Jan 1 00:00:00 1970 From: leonard.crestez@nxp.com (Leonard Crestez) Date: Wed, 3 May 2017 20:58:18 +0300 Subject: [PATCH] ARM: dts: imx6sx-sdb: Remove cpufreq OPP override In-Reply-To: References: <89cc7192100bdc9ce546bf6000446e629457ebc1.1493138693.git.leonard.crestez@nxp.com> <1493141004.3557.8.camel@nxp.com> <20170503135715.GG18578@dragon> <76e22a7e-590f-00ee-04f8-87604303eaad@denx.de> <1493823533.11226.28.camel@nxp.com> Message-ID: <1493834298.11226.40.camel@nxp.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, 2017-05-03 at 17:59 +0200, Marek Vasut wrote: > On 05/03/2017 04:58 PM, Leonard Crestez wrote: > > On Wed, 2017-05-03 at 16:26 +0200, Marek Vasut wrote: > > > 2) It actually fixes a problem with the voltage rails such that the DVFS > > > ???works without leaving the system in unstable or dead state. You do > > > ???need the second part of my patch if you drop the OPP hackery, without > > > ???it the power framework cannot correctly configure the core voltages, > > > ???so the patch from Leonard makes things worse. > > No, I think there is a misunderstanding here. The second part of your > > patch will cause cpufreq poking at LDOs to indirectly adjust the input > > from the PMIC to the minimum required (this is LDO target + > > min_dropout_uv). Without it by default VDD_ARM_SOC_IN will remain fixed > > as 1375mV from boot. > Who sets / guarantees that default value for ARM and SOC rails ? I think it's from the PMIC hardware itself (but maybe uboot plays with it). VDD_ARM_SOC_IN on this board is tied to SW1AB from MMPF0200: http://www.nxp.com/assets/documents/data/en/data-sheets/MMPF0200.pdf It seems reasonable to rely on such voltages set externally. > With the OPP override in place, there's at least the guarantee that both > rails will have the same voltage requirement. If you remove the OPP > override without modeling the actual regulator wiring, the guarantee is > gone. The imx6sx chip has internal LDO_ARM and LDO_SOC regulators which can generate separate voltages for arm/soc. The fact that these regulators share the same supply is only an issue when they are set in bypass mode. However the boot issues happen on REV C but apparently not REV B of the board. I don't have a good explanation for this so maybe I am missing something. --? Regards, Leonard