On Tue, Apr 14, 2015 at 5:17 PM, Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > On Tue, Apr 14, 2015 at 02:49:04PM -0500, Kumar Gala wrote: >> On Apr 14, 2015, at 11:36 AM, Mark Rutland <mark.rutland@xxxxxxx> wrote: >> > On Fri, Apr 10, 2015 at 11:05:29AM +0100, Catalin Marinas wrote: >> >> On Thu, Apr 09, 2015 at 12:37:06PM -0500, Kumar Gala wrote: >> >>> This patch set adds support for SMP boot on the MSM8x16 family of Qualcomm SoCs. >> >>> >> >>> To support SMP on the MSM8x16 SoCs we need to add ARMv8/64-bit SCM interfaces to >> >>> setup the boot/release addresses for the secondary CPUs. In addition we need >> >>> a uniquie set of cpu ops. I'm aware the desired methods for booting secondary >> >>> CPUs is either via spintable or PSCI. However, these SoCs are shipping with a >> >>> firmware that does not support those methods. >> >> >> >> And the reason is? Some guesses: >> >> >> >> a) QC doesn't think boot interface (and cpuidle) standardisation is >> >> worth the effort (to put it nicely) >> >> b) The hardware was available before we even mentioned PSCI >> >> c) PSCI is not suitable for the QC's SCM interface >> >> d) Any combination of the above >> >> >> >> I strongly suspect it's point (a). Should we expect future QC hardware >> >> to do the same? >> >> >> >> You could argue the reason was (b), though we've been discussing PSCI >> >> for at least two years and, according to QC press releases, MSM8916 >> >> started sampling in 2014. >> >> >> >> The only valid reason is (c) and if that's the case, I would expect a >> >> proposal for a new firmware interface protocol (it could be PSCI-based), >> >> well documented, that can be shared with others that may encounter the >> >> same shortcomings. >> > >> > There's no need to even fork PSCI. The PSCI specification will evolve >> > over time as vendors request changes and we try to accomodate them. >> > >> > If there's something that PSCI doesn't do that you need it to, contact >> > ARM. Other vendors already have. > > Mostly yes but there may be valid reasons for not being able to use > PSCI. The spin-table method is still a firmware interface, though not > necessarily secure (a.k.a. SMC-based). The ACPI parking protocol is > another and, who knows, maybe we define a way to park CPUs back to > firmware without SMC calls (when EL3 is not available). > >> But what is someone to do between the period of getting PSCI spec >> updated and needing to ship a product with firmware? >> >> The take still sounds like if you don’t implement an exact version of >> PSCI you are screwed from being supported in the upstream ARM64 >> kernel. > > These are silly arguments. There is a big difference between "we > couldn't get the firmware implementing the standard for the early > silicon but we are working on fixing it for future revisions" vs. "we > don't give a s**t about these standards, the kernel must be inclusive". > So please make up your mind on which direction you want to pursue. > Just speaking as an outsider to this topic, but seems like most/all tablets/phones/etc ship with signed firmware. Which means for most of the population, upgrading the firmware to a new version which did support the standard (assuming it existed), isn't really an option on our devices, any more than fixing buggy acpi tables is on our laptops.. BR, -R > -- > Catalin > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
