On 13/04/17 07:27, Peng Fan wrote: Hi,
>> -----Original Message----- >> From: Stefano Babic [mailto:sba...@denx.de] >> Sent: Thursday, April 13, 2017 2:24 PM >> To: Peng Fan <peng....@nxp.com>; Stefano Babic <sba...@denx.de> >> Cc: van.free...@gmail.com; u-boot@lists.denx.de; andre.przyw...@arm.com; >> Albert ARIBAUD <albert.u.b...@aribaud.net> >> Subject: Re: [PATCH 1/2] imx-common: Enable ACTLR.SMP bit for i.MX cortex- >> a7 platforms >> >> Hi Peng, >> >> On 13/04/2017 05:05, Peng Fan wrote: >> >>>> Anyway, it looks to me wrong to fix this in i.MX code, as this must >>>> be fixed for all Cortex-A7. It should be fixed in general ARM code. >>>> >>>> And Andre has already sent patches for this (at least for sunxi), but >>>> with the opposite rule (default is set if not specific requested). >>> >>> Thanks for correcting me. I see Andre's patch >>> https://lists.denx.de/pipermail/u-boot/2017-February/279918.html >>> >>> It only handles sunxi platform. If we need fix i.MX A7 cores, do you prefer >>> I >> set the SMP bit in s_init for i.MX6UL/7? >>> Or you prefer this should be handled by common ARM code? >> >> As far as I understand, this issue is common to all A7 cores ==> fix should >> be in >> common ARM code. Well, it's not only common to all A7 cores, actually all ARMv7 SMP Cortex cores (A5, A7, A9, A15, A17) need this. Cortex-A8 is UP only, so does not have this bit. Sometimes this bit is set by other boot code before U-Boot (hence not every board might need this). ARMv8 Cortex cores have this bit as well, just in the CPUECTLR register. So looking at arm64, I find (in arch/arm/cpu/armv8/Kconfig): ============ config ARMV8_SET_SMPEN bool "Enable data coherency with other cores in cluster" help Say Y here if there is not any trust firmware to set CPUECTLR_EL1.SMPEN bit before U-Boot. .... ============ So I'd suggest to piggy back on this, either by moving this Kconfig option to some shared ARM code path, or by replicating this option to some ARMv7 Kconfig file. > Ok. Since there is no Cortex-A[x] revision check in U-Boot, need to first add > the code. Mmh, do you mean auto-detection during runtime? As in: if (MIDR == CortexA7) set_smp_bit(); The problem with this is that U-Boot might not be able to access the register (access to ACTLR from non-secure world can be forbidden by secure world). So I'd go with a Kconfig option. Boards or platforms that need it could just select it. We just need to find a nice place to put the code, maybe in arch/arm/cpu/armv7/start.S. And another problem is that is needs to be set on every core in the system (like arch/arm/cpu/armv7/psci.S does already in psci_enable_smp). So it cannot really work for systems without PSCI or those not bringing all cores into U-Boot. Cheers, Andre. > Then set ACTLR.SMP for A7 SMP. > > Regards, > Peng. > _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
