Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 18 Mar 2024 14:31:30 -0700 | Subject | Re: [PATCH v4 1/2] of: create of_root if no dtb provided | From | Guenter Roeck <> |
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On 3/18/24 12:26, Rob Herring wrote: > +Stephen > > On Mon, Mar 18, 2024 at 12:09 PM Guenter Roeck <linux@roeck-us.net> wrote: >> >> Hi, >> >> On Fri, Mar 17, 2023 at 12:34:14AM -0500, Frank Rowand wrote: >>> When enabling CONFIG_OF on a platform where of_root is not populated by >>> firmware, we end up without a root node. In order to apply overlays and >>> create subnodes of the root node, we need one. Create this root node >>> by unflattening an empty builtin dtb. >>> >>> If firmware provides a flattened device tree (FDT) then the FDT is >>> unflattened via setup_arch(). Otherwise setup_of(), which is called >>> immediately after setup_arch(), will create the default root node >>> if it does not exist. >>> >>> Signed-off-by: Frank Rowand <frowand.list@gmail.com> >> >> This patch results in a crash on nios2. > > This patch was never applied. I assume you meant a later version of it > that did get applied. > >> >> Building nios2:10m50-ghrd:10m50_defconfig:10m50_devboard.dts ... running ...R failed (crashed) > > Booting with DT? > >> ------------ >> qemu log: >> earlycon: uart8250 at MMIO32 0x18001600 (options '') >> printk: legacy bootconsole [uart8250] enabled >> Linux version 6.8.0-11409-gf6cef5f8c37f (groeck@desktop) (nios2-linux-gcc (GCC) 11.4.0, GNU ld (GNU Binutils) 2.40) #1 Sun Mar 17 23:38:59 PDT 2024 >> Kernel panic - not syncing: early_init_dt_alloc_memory_arch: Failed to allocate 72 bytes align=0x40 >> ---[ end Kernel panic - not syncing: early_init_dt_alloc_memory_arch: Failed to allocate 72 bytes align=0x40 ]--- > > nios2 looks utterly broken to me. This change should be a nop unless > initial_boot_params is NULL. It looks like it is possible for r6 (dtb > address) to be 0 depending on kconfig options, but that would have > skipped copying and unflattening which would then panic in > setup_cpuinfo(). If initial_boot_params is not NULL, then the same > early_init_dt_alloc_memory_arch() calls should fail when copying the > DT. So I don't see how nios2 booting with DT ever worked. >
For nios2, in early_init_devtree():
void __init early_init_devtree(void *params) { __be32 *dtb = (u32 *)__dtb_start; ... if (be32_to_cpu((__be32) *dtb) == OF_DT_HEADER) params = (void *)__dtb_start;
That worked fine until this patch. Starting with this patch, __dtb_start always points to a valid empty devicetree blob, which overrides the devicetree blob passed to early_init_devtree(). This causes the problem.
Guenter
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