On 02/19/2013 01:26 PM, Wolfgang Denk wrote:
Dear Rob Herring,
In message 1359085160-28675-1-git-send-email-robherring2@gmail.com you wrote:
Currently, u-boot will always fixup the DT memory node on ARM. If the dtb has correct memory information, then we don't want or need u-boot to touch the memory node. Allow platforms to skip this by not filling in dram bank information.
Well, if this is what you want, then please implement just this, and do not do much more.
void __dram_init_banksize(void) { +#if CONFIG_NR_DRAM_BANKS gd->bd->bi_dram[0].start = CONFIG_SYS_SDRAM_BASE; gd->bd->bi_dram[0].size = gd->ram_size; +#endif }
This change will leave the memory information in struct bd_info uninitialized, so the "bdinfo" command will print just bogus data.
This is not a good idea.
This hunk can be dropped I think.
--- a/arch/arm/lib/bootm.c +++ b/arch/arm/lib/bootm.c @@ -79,6 +79,7 @@ void arch_lmb_reserve(struct lmb *lmb) #ifdef CONFIG_OF_LIBFDT static int fixup_memory_node(void *blob) { +#if CONFIG_NR_DRAM_BANKS bd_t *bd = gd->bd; int bank; u64 start[CONFIG_NR_DRAM_BANKS]; @@ -90,6 +91,9 @@ static int fixup_memory_node(void *blob) }
return fdt_fixup_memory_banks(blob, start, size, CONFIG_NR_DRAM_BANKS); +#else
- return 0;
+#endif
I dislike this. If you want to make a property of your device tree "immutable", then you should mark it there as such. Instead of removing the code here, U-Boot should then check for such a property and leave the value unchanged.
There is no such way defined to flag that and I'm not going to invent one. It's not that the memory node is immutable, but the default should not be "needs fixups". No one puts purposely wrong data in their DT. So therefore all data should be immutable? What happens when we need to fixup immutable data?
What I would really prefer to do is like powerpc where platforms override this if they need the fixup and the default behavior is no fixup. But that would require knowing which platforms do and don't need the fixup. It only going to get harder to change that.
Actually you are reaching here a point where it seems necessary that U-Boot itself is able to read the DT to configure itself correctly, i. e. the memory size information it holds should then also be extracted from the DT.
I thought about doing this. That's really an orthogonal issue. The problem is you cannot adjust the amount of memory u-boot uses to be different than the amount of RAM in the /memory node. If you adjust the size in u-boot, the adjusted size is passed to the kernel no matter what.
There's issues with LPAE systems having >4GB of RAM as all the size and address values are 32-bit. This could be fixed, but I'm not sure there is much value in u-boot knowing about memory above 4GB as it can't really access all of it and it would be purely informational.
Rob
Best regards,
Wolfgang Denk