From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Rini Date: Mon, 12 Apr 2021 14:18:18 -0400 Subject: [PATCH] Revert "spl: Drop bd_info in the data section" In-Reply-To: References: <23de53fe-e0be-9fe8-1e59-fd1e0a2104d6@gmail.com> <20210409205312.GL1310@bill-the-cat> <20210412132546.GS1310@bill-the-cat> <20210412144044.GT1310@bill-the-cat> <043c5ab0-8176-97f2-88fb-50c7ce914cf6@gmail.com> <20210412162640.GX1310@bill-the-cat> Message-ID: <20210412181818.GY1310@bill-the-cat> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On Tue, Apr 13, 2021 at 05:49:19AM +1200, Simon Glass wrote: > Hi Tom, Alex, > > On Tue, 13 Apr 2021 at 04:26, Tom Rini wrote: > > > > On Mon, Apr 12, 2021 at 10:21:18AM -0500, Alex G. wrote: > > > > > > > > > On 4/12/21 9:40 AM, Tom Rini wrote: > > > > On Mon, Apr 12, 2021 at 08:51:11AM -0500, Alex G. wrote: > > > > > > > > > > > > > > > On 4/12/21 8:25 AM, Tom Rini wrote: > > > > > > On Fri, Apr 09, 2021 at 05:29:36PM -0700, Tim Harvey wrote: > > > > > > > On Fri, Apr 9, 2021 at 1:53 PM Tom Rini wrote: > > > > > > > > > > > > > > > > On Fri, Apr 09, 2021 at 03:24:41PM -0500, Adam Ford wrote: > > > > > > > > > On Fri, Apr 9, 2021 at 2:20 PM Alex G. wrote: > > > > > > > > > > > > > > > > > > > > Hi Simon > > > > > > > > > > > > > > > > > > > > On 4/8/21 6:55 PM, Simon Glass wrote: > > > > > > > > > > > Hi Alexandru, > > > > > > > > > > > > > > > > > > > > > > On Fri, 9 Apr 2021 at 04:56, Alexandru Gagniuc wrote: > > > > > > > > > > > > > > > > > > > > > > > > This reverts commit 38d6b7ebdaee3e0e8426ef1b9df88bdce8ae2e75. > > > > > > > > > > > > > > > > > > > > > > > > struct global_data contains a pointer to the bd_info structure. This > > > > > > > > > > > > pointer was populated spl_set_bd() to a pre-allocated bd_info in the > > > > > > > > > > > > ".data" section. The referenced commit replaced this mechanism to one > > > > > > > > > > > > that uses malloc(). That new mechanism is only used if SPL_ALLOC_BD=y. > > > > > > > > > > > > which very few boards do. > > > > > > > > > > > > > > > > > > > > > > > > The result is that (struct global_data)->bd is NULL in SPL on most > > > > > > > > > > > > platforms. This breaks falcon mode, since arch_fixup_fdt() tries to > > > > > > > > > > > > access (struct global_data)->bd and set the "/memory" node in the > > > > > > > > > > > > devicetree. The result is that the "/memory" node contains garbage > > > > > > > > > > > > values, causing linux to panic() as it sets up the page table. > > > > > > > > > > > > > > > > > > > > > > > > Instead of trying to fix the mess, potentially causing other issues, > > > > > > > > > > > > revert to the code that worked, while this change is reworked. > > > > > > > > > > > > > > > > > > > > > > The goal here is to drop a feature that few boards use and reduce > > > > > > > > > > > memory usage in SPL. It has been in place for two releases now. > > > > > > > > > > > > > > > > > > > > > > If Falcon mode needs it, perhaps you could add an 'imply' in the > > > > > > > > > > > Kconfig for that feature? Is there one? Or perhaps > > > > > > > > > > > CONFIG_ARCH_FIXUP_FDT_MEMORY ? > > > > > > > > > > > > > > > > > > > > > > One option would be to return an error in arch_fixup_fdt(). In > > > > > > > > > > > general, fixups make things tricky because there is no way to > > > > > > > > > > > determine when they are used but at least this one has a CONFIG. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > The argument that this has been in place for two releases is incorrect. > > > > > > > > > > Commit 38d6b7ebdaee3e0e8426ef1b9df88bdce8ae2e75 was only introduced with > > > > > > > > > > the v2021.04 release. It definitely was not in 2021.01. It's only in the > > > > > > > > > > last release, which is four days old t the time of this writing. > > > > > > > > > > > > > > > > Yes. But another way of saying that is that we're 4 days in to the > > > > > > > > merge window. That's a bit early to say we must revert the change. If > > > > > > > > this was just before the release, yes, revert would be the right answer. > > > > > > > > It's also the case the original commit fixes some cases while also > > > > > > > > saving size, if I read it right. So a strict revert isn't right, we'd > > > > > > > > need to also probably also default y SPL_ALLOC_BD in some cases. > > > > > > > > > > > > > > > > > > Although I was able to find one example, the reality is that we don't > > > > > > > > > > know the full extent of the breakage. The prudent thing at this point is > > > > > > > > > > to revert. > > > > > > > > > > > > > > > > > > > > The knowledge of how to init the platform is in the devicetree and code. > > > > > > > > > > Why should kconfig also be involved in storing this knowledge? By this > > > > > > > > > > model, as the number of boards increases without bounds, every "if" > > > > > > > > > > predicate tends to be Kconfig driven. That is not maintainable, and why > > > > > > > > > > I think the original change --and the proposed fixes-- are broken by design. > > > > > > > > > > > > > > > > > > > > Furthermore, I'm happy to discuss what to do about Falcon mode, and if > > > > > > > > > > we should kill it entirely (I have an alternative proposal). But we > > > > > > > > > > shouldn't have that discussion in a manner holding my platform hostage. > > > > > > > > > > To be fair to you, I don't think reverting a 64-byte savings in .data > > > > > > > > > > will hold your platform hostage either. > > > > > > > > > > > > > > > > > > That original patch broke a bunch of OMAP boards, but enabling > > > > > > > > > SPL_ALLOC_BD was the solution to fix the issue. > > > > > > > > > Can you try enabling SPL_ALLOC_BD and see if that fixes it? Maybe we > > > > > > > > > can make falcon mode imply it. > > > > > > > > > > > > > > > > It would be "select" since it needs it rather than imply. > > > > > > > > > > > > > > > > > > > > > > I just ran into this as well finding that commit 38d6b7ebdaee ("spl: > > > > > > > Drop bd_info in the data section") breaks Gateworks Ventana and > > > > > > > defining SPL_ALLOC_BD does resolve it. In this case, Falcon mode is > > > > > > > not being used and the breakage is because arch/arm/mach-imx/spl.c > > > > > > > dram_init_banksize() accesses gd->bd which is NULL. > > > > > > > > > > > > > > So I would guess that this probably broke a whole lot of IMX based > > > > > > > boards that use SPL. > > > > > > > > > > > > > > I don't quite know what the best solution is... we now have a v2021.04 > > > > > > > that is broken for several or many boards and I dont' know if its > > > > > > > clear what cases break. > > > > > > > > > > > > Looking forward, I think we need to rework this. Simon, I gather you > > > > > > have some platforms where we need to set gd->bd to something that we > > > > > > malloc() ? So perhaps spl_set_bd() should have been __weak so that > > > > > > architectures / platforms could override as needed, but also move it > > > > > > just past mem_malloc_init(). > > > > > > > > > > Let's try and avoid making new weak functions. Why not introduce a > > > > > spl_platform_alloc_bd(), that each plat- *must* implement? No diversion to > > > > > Kconfig and no __weak__ required. > > > > > > > > Well, who needs something different than what we had before exactly? > > > > > > I'm not sure. From reading the commit message of the broken change, it seems > > > the main driver was to save 64 bytes on coral. I'm assuming coral is the > > > codename for a platform. > > > > Yes, coral is an x86 chromebook. It also says: > > This uses up space in the SPL binary but it always starts as zero. > > Also some boards cannot support data in TPL (e.g. Intel Apollo Lake). > > > > and defaults the new feature to enabled on all x86. And there's > > a comment about x86 in the function (that with the changes made isn't so > > helpful/correct?) now too. So yes, I want to see what Simon > > > > > > This shouldn't be kicked up to "every SoC must define...", but maybe > > > > "every architecture must define..." is OK. Or maybe it's really just "a > > > > few unusual platforms need" and so a weak function makes sense. > > > > > > We can can have arch_spl_alloc_bd() instead of plat_(). I don't believe in > > > weak functins, as I see them as the problems that "made sense at the time". > > > > I see weak functions as a good solution when the problem is something > > where the majority of the (cross-platform) cases require the same > > solution, but there's one or two oddities out there. But regardless, we > > need to have the problem better defined before we can propose a > > solution. > > So how about enabling the Kconfig for iMX? I am not sure how many > platforms do actually need this feature? That was an OK answer for the first group we hit this on. > Another option might be to (just as a test) take the 'bd' out of > global_data when the Kconfig is not defined, to find out which > platforms use it? And that might help us figure out the second grouping of platforms, yes. > As to a weak function, what would the default behaviour be? If we can > define that, then it would be better IMO. > > When we try to refactor things, weak functions and undefined (or > arch-specific behaviour) can really make things tough. Well, what was the problem you were trying to solve here? I assumed there was a case where things actively broke, with the previous design, and it's not just the 64byte savings in some cases. But is it? -- Tom -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 659 bytes Desc: not available URL: