Re: [PATCH v4] ARM: configs: Add Freescale LS1021A defconfig

From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: Huan Wang <alison.wang@freescale.com>,
	Jin Jason <Jason.Jin@freescale.com>,
	Russell King - ARM Linux <linux@arm.linux.org.uk>,
	Fabio Estevam <festevam@gmail.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"shawnguo@kernel.org" <shawnguo@kernel.org>
Subject: Re: [PATCH v4] ARM: configs: Add Freescale LS1021A defconfig
Date: Wed, 14 Oct 2015 14:54:48 +0200	[thread overview]
Message-ID: <5232654.e6dagm53H4@wuerfel> (raw)
In-Reply-To: <BN3PR0301MB086733D602580A5A9EBF150EFE3F0@BN3PR0301MB0867.namprd03.prod.outlook.com>

On Wednesday 14 October 2015 10:18:47 Huan Wang wrote:
> > On Thursday 24 September 2015 07:27:10 Huan Wang wrote:
> > > > On Fri, Sep 18, 2015 at 4:38 AM, Huan Wang
> > > > <alison.wang@freescale.com>
> > > > wrote:
> > > >
> > > > > [Alison Wang] Thanks for your reply. I agreed with you about
> > > > > creating a new multi_v7_lpae_defconfig. In
> > > > > multi_v7_lpae_defconfig, I need to add the following CONFIG_XX to
> > > > > support LS1021A based on
> > > > multi_v7_defconfig.
> > > > >
> > > > > CONFIG_ARM_LPAE=y
> > > > > CONFIG_VMSPLIT_2G=y
> > > >
> > > > Is CONFIG_VMSPLIT_2G=y really needed?
> > > [Alison Wang] I tried to remove CONFIG_VMSPLIT_2G and used the default
> > > CONFIG_VMSPLIT_3G, but kernel could not boot up. It hangs at " Starting
> > kernel ... ".
> > >
> > > Any suggestion? Thanks.
> > 
> > Try enabling DEBUG_LL for your platform to get some debug output, if  you
> > still don't get any helpful messages, try also inserting
> > 
> >       printascii(__func__);
> > 
> > statements in the early boot process to see how far you get before the hang.
> > 
> [Alison Wang] I can get to __turn_mmu_on or later, but I could not get the print
> message "Booting Linux on physical CPU 0xf00" in smp_setup_processor_id().
> 
> I guess something wrong with the initial page tables in __create_page_tables,
> as for CONFIG_VMSPLIT_3G, only PAGE_OFFSET is changed from 0x80000000 to 0xC0000000.
> BTW, on our platform, TEXT_OFFSET is 0x00008000, PHYS_OFFSET is 0x80000000.
> 
> Any suggestion? Thanks.

My first guess is that there is something wrong with your debug_ll implementation,
as that would explain why you can't get anything to the console after
turning on page tables.

It looks like ls1021a uses lpuart, but I can't even see an implementation for
that in arch/arm/include/debug/. What code do you use for printing?

	Arnd