+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. Rob
