On 14/04/2020 16:00, Rob Herring wrote: > +Karol > > On Mon, Jan 13, 2020 at 5:12 AM Jon Hunter <jonathanh@xxxxxxxxxx> wrote: >> >> >> On 10/01/2020 23:50, Rob Herring wrote: >>> On Tue, Jan 7, 2020 at 4:22 AM Jon Hunter <jonathanh@xxxxxxxxxx> wrote: >>>> >>>> Hi Rob, >>>> >>>> On 11/12/2019 23:23, Rob Herring wrote: >>>>> The phandle cache was added to speed up of_find_node_by_phandle() by >>>>> avoiding walking the whole DT to find a matching phandle. The >>>>> implementation has several shortcomings: >>>>> >>>>> - The cache is designed to work on a linear set of phandle values. >>>>> This is true for dtc generated DTs, but not for other cases such as >>>>> Power. >>>>> - The cache isn't enabled until of_core_init() and a typical system >>>>> may see hundreds of calls to of_find_node_by_phandle() before that >>>>> point. >>>>> - The cache is freed and re-allocated when the number of phandles >>>>> changes. >>>>> - It takes a raw spinlock around a memory allocation which breaks on >>>>> RT. >>>>> >>>>> Change the implementation to a fixed size and use hash_32() as the >>>>> cache index. This greatly simplifies the implementation. It avoids >>>>> the need for any re-alloc of the cache and taking a reference on nodes >>>>> in the cache. We only have a single source of removing cache entries >>>>> which is of_detach_node(). >>>>> >>>>> Using hash_32() removes any assumption on phandle values improving >>>>> the hit rate for non-linear phandle values. The effect on linear values >>>>> using hash_32() is about a 10% collision. The chances of thrashing on >>>>> colliding values seems to be low. >>>>> >>>>> To compare performance, I used a RK3399 board which is a pretty typical >>>>> system. I found that just measuring boot time as done previously is >>>>> noisy and may be impacted by other things. Also bringing up secondary >>>>> cores causes some issues with measuring, so I booted with 'nr_cpus=1'. >>>>> With no caching, calls to of_find_node_by_phandle() take about 20124 us >>>>> for 1248 calls. There's an additional 288 calls before time keeping is >>>>> up. Using the average time per hit/miss with the cache, we can calculate >>>>> these calls to take 690 us (277 hit / 11 miss) with a 128 entry cache >>>>> and 13319 us with no cache or an uninitialized cache. >>>>> >>>>> Comparing the 3 implementations the time spent in >>>>> of_find_node_by_phandle() is: >>>>> >>>>> no cache: 20124 us (+ 13319 us) >>>>> 128 entry cache: 5134 us (+ 690 us) >>>>> current cache: 819 us (+ 13319 us) >>>>> >>>>> We could move the allocation of the cache earlier to improve the >>>>> current cache, but that just further complicates the situation as it >>>>> needs to be after slab is up, so we can't do it when unflattening (which >>>>> uses memblock). >>>>> >>>>> Reported-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> >>>>> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> >>>>> Cc: Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx> >>>>> Cc: Frank Rowand <frowand.list@xxxxxxxxx> >>>>> Signed-off-by: Rob Herring <robh@xxxxxxxxxx> >>>> >>>> With next-20200106 I have noticed a regression on Tegra210 where it >>>> appears that only one of the eMMC devices is being registered. Bisect is >>>> pointing to this patch and reverting on top of next fixes the problem. >>>> That is as far as I have got so far, so if you have any ideas, please >>>> let me know. Unfortunately, there do not appear to be any obvious errors >>>> from the bootlog. >>> >>> I guess that's tegra210-p2371-2180.dts because none of the others have >>> 2 SD hosts enabled. I don't see anything obvious though. Are you doing >>> any runtime mods to the DT? >> >> I have noticed that the bootloader is doing some runtime mods and so >> checking if this is the cause. I will let you know, but most likely, >> seeing as I cannot find anything wrong with this change itself. > > Did you figure out the problem here? Karol sees a similar problem on > Tegra210 with the gpu node regulator. > > It looks like /external-memory-controller@7001b000 has a duplicate > phandle. Comparing the dtb in the filesystem with what the kernel > gets, that node is added by the bootloader. So the bootloader is > definitely creating a broken dtb. Yes it was caused by the bootloader, u-boot, incorrectly copying some nodes. After preventing u-boot from doing that, it was fine. There are some u-boot environment variables [0] that you can try clearing to prevent this. Alternatively, if you use a upstream u-boot that should also work. Cheers Jon [0] https://elinux.org/Jetson/TX1_Upstream_Kernel#Upstream_Linux_kernel -- nvpublic
