Hi Kever, On Tue, 21 Nov 2017 at 03:24, Kever Yang <kever.y...@rock-chips.com> wrote: > > Hi Simon, >
There are a lot of points in here, so I will spread my comments throughout your email. > In order to make people easier to maintain a U-Boot for product, > > we want to re-use the dtb from kernel. Some peripheral like power/pmic > > and display panel, key, charger which need work in U-Boot and may different > > in different product, we want to make people only maintain kernel dts, > but not > > one more U-Boot project for all these devices. That sounds like a good idea. The U-Boot and kernel .dts should be the same. But in some cases we may need changes made to the kernel version to support U-Boot. Unfortunately this has proven quite tricky and I'm not aware of any U-Boot change that has been accepted. Admittedly I have not tried for a number of years, so perhaps the reviewers are more amenable now. > > I want to do this just around the > > relocate, need to read dtb from storage like emmc/nand/spi, and then use > > a new dtb for initr_dm after relocate. This seems OK, but why? Do you mean that U-Boot should read the kernel's DTB and use that after relocation? The problem is that it needs to be loaded from somewhere, and you need the DT for U-Boot to work. So you add a pre-reloc DT with just enough drivers for loading the post-reloc DT. But why bother? You may as well just load the full thing. > > Here are issues I have met: > > - The kernel dts may not have a stdout in chosen, we may use earlycon, > earlyprintk instead; I suppose U-Boot could support this, but IMO it would be better to upstream the change for stdout. > > this lead to U-Boot can not find a serial driver after relocate; > > - no alias for mmc device which is need by U-Boot but not used in kernel; Again, we could upstream a change. > > - not able to init mmc driver twice with current driver; > > mmc driver not able to work before relocate, no bss for (static int > initialized), and hang even Well you cannot access BSS before relocation. If you use DM then it should not need to access BSS. You should be able to use the uclass-private data instead. > > if I skip this; > > mmc driver can init and read dtb before initr_dm, but not able to > init again after initr_dm. Why not? That seems like a bug. > > > In fact, I don't think we have to re-init serial driver and mmc driver, > and most other driver which > > need pre-relocate like clock, the only driver I have seem have different > use in pre-relocate and post-relocate Yes that's true, but the idea has never been implemented. > > is video driver(no idea why it have to be pre-relocate, we always have > display very late), The video driver is only inited before relocation to find out the amount of memory it needs to be allocated. It does not actually probe it fully. > > can we add a tag for re-use the dm driver data for those with pre-relocate ? Yes I think it could work like this: - initr_dm() remembers the old dm_root pointer - post-reloc drivers can request access to the priv/platdata/uc_priv from before relocation, e.g. using: int dm_get_pre_reloc_dev(struct udevice *dev, struct udevice *pre_reloc_devp); this returns the pre-reloc device associated with the post-reloc device 'dev', if available. Regards, Simon _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
