From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@armlinux.org.uk (Russell King - ARM Linux) Date: Fri, 19 May 2017 18:15:26 +0100 Subject: [CFT] Always enable SMP mode on MP capable CPUs In-Reply-To: References: <20170518105209.GN22219@n2100.armlinux.org.uk> Message-ID: <20170519171526.GW22219@n2100.armlinux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, May 19, 2017 at 02:07:28PM -0300, Fabio Estevam wrote: > On Thu, May 18, 2017 at 3:09 PM, Fabio Estevam wrote: > > > I tested this patch on a mx6ul, which is CortexA7 UP using USB serial > > download mode. > > > > In this boot mode the ROM code does not set the SMP bit and I can > > notice a very slow boot progress with CONFIG_SMP=n with an original > > 4.12-rc1. > > > > With this patch applied it boots with the correct speed, so: > > However the kernel still takes a long time to decompress when the > bootloader or ROM does not set the SMP bit. > > After it decompress, then it boots quickly. > > Should the SMP bit be set inside arch/arm/boot/compressed/head.S? We could expand the table to positively identify the SMP capable CPUs and enable the SMP bit there, but it's going to add a lot of entries there (one for each specific ARMv7 MP CPU) and is going to have to be endlessly added to each time a new SMP CPU comes out. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.