Hi, Rob, 2011/1/27 Rob Herring <[email protected]>: > On 01/26/2011 02:04 PM, John Linn wrote: >>> >>> -----Original Message----- >>> From: Grant Likely [mailto:[email protected]] On Behalf Of Grant >>> Likely >>> Sent: Tuesday, January 18, 2011 1:29 PM >>> To: [email protected] >>> Cc: Nicolas Pitre; Russell King; Catalin Marinas; >>> [email protected]; linux- >>> [email protected]; Olof Johansson; Jeremy Kerr; John Linn; Lennert >>> Buijtenhek >>> Subject: [PATCH 0/8] Basic ARM device tree support >>> >>> It's been a while since these patches have been circulated for review. >>> Much has changed since the last posting and there are no longer any >>> ugly hacks or workarounds to it working. From my viewpoint, these >>> patches are complete and ready to be used. >>> >>> This patch series allows CONFIG_OF to be enabled on ARM and allows the >>> kernel to accept a dtb pointer from boot firmware instead of atags. >>> If a dtb is passed, then the kernel will use the root 'compatible' >>> property to find a matching machine_desc, and it will use it to obtain >>> the memory layout, initrd location and kernel parameters string. >>> >>> Only limited device tree support is enabled here. It does not perform >>> any kind of device registration from device tree data. That support >>> will be enabled in a later patch set. Right now those patches depend >>> on the common struct clk patches that Jeremy is working on, so I'm not >>> going to post them yet. Rather, this series is a stable base that >>> other engineers can use to start working on device tree support for >>> their platforms. >>> >>> Tested on Versatile (qemu) and nVidia Tegra Harmony. Kernel compiles >>> an boot with CONFIG_OF both on and off, both with and without passing >>> a device tree blob. >> >> Tested on Xilinx platform. Did see an issue with loading the device >> tree blob into higher memory. At address 0 there was no issue. >> > > I have a fix for this. The issue is the early mmu page table needs to map > the dtb. I later realized this is also may be problem for ATAGs as well, so > I planned to re-work to make it unconditional and work for ATAGs. Or perhaps > ATAGs only get accessed with the MMU on later than the dtb and everything is > okay? > > This applies to the DT patch set prior to the one Grant sent out > this week, so it may need updates. > > From: Rob Herring <[email protected]> > Date: Tue, 5 Oct 2010 10:32:51 -0500 > Subject: [PATCH] arm/dt: map devtree blob in initial page table > > If the DTB is not in 1st 1MB of RAM, it will not be mapped before > memblock is setup, so map it early. We assume the dtb is less than > 1MB and map 2MB so it can be at any alignment. > > Some assembly optimizations from Nicolas Pitre. > > Signed-off-by: Rob Herring <[email protected]> > --- > arch/arm/kernel/head.S | 13 +++++++++++++ > 1 files changed, 13 insertions(+), 0 deletions(-) > > diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S > index 0480f25..1fcb962 100644 > --- a/arch/arm/kernel/head.S > +++ b/arch/arm/kernel/head.S > @@ -228,6 +228,19 @@ __create_page_tables: > .endif > str r6, [r0] > > +#ifdef CONFIG_OF_FLATTREE > + /* Make sure DT blob is mapped */ > + adr r0, __devtree_pointer > + ldr r0, [r0] > + mov r0, r0, lsr #20 > + mov r0, r0, lsl #20 > + add r3, r0, #PAGE_OFFSET > + add r3, r4, r3, lsr #18 > + orr r6, r7, r0 > + str r6, [r3] > + add r6, r6, #0x100000 > + str r6, [r3, #4] > +#endif > #ifdef CONFIG_DEBUG_LL > #ifndef CONFIG_DEBUG_ICEDCC
Build broken after apply your patch, arch/arm/kernel/head.S:223: Error: undefined symbol __devtree_pointer used as an immediate value make[2]: *** [arch/arm/kernel/head.o] Error 1 BR, Jason Liu > /* > -- > > _______________________________________________ > linux-arm-kernel mailing list > [email protected] > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
