Hi David, On Mon, Feb 19, 2024 at 04:33:17PM -0600, David Lechner wrote: > This is a follow-up to [1] where it was suggested to break down the > proposed SPI offload support into smaller series. > > This takes on the first suggested task of introducing an API to > "pre-cook" SPI messages. This idea was first discussed extensively in > 2013 [2][3] and revisited more briefly 2022 [4]. > > The goal here is to be able to improve performance (higher throughput, > and reduced CPU usage) by allowing peripheral drivers that use the > same struct spi_message repeatedly to "pre-cook" the message once to > avoid repeating the same validation, and possibly other operations each > time the message is sent. > > This series includes __spi_validate() and the automatic splitting of > xfers in the optimizations. Another frequently suggested optimization > is doing DMA mapping only once. This is not included in this series, but > can be added later (preferably by someone with a real use case for it). > > To show how this all works and get some real-world measurements, this > series includes the core changes, optimization of a SPI controller > driver, and optimization of an ADC driver. This test case was only able > to take advantage of the single validation optimization, since it didn't > require splitting transfers. With these changes, CPU usage of the > threaded interrupt handler, which calls spi_sync(), was reduced from > 83% to 73% while at the same time the sample rate (frequency of SPI > xfers) was increased from 20kHz to 25kHz. > > [1]: https://lore.kernel.org/linux-spi/20240109-axi-spi-engine-series-3-v1-1-e42c6a986580@xxxxxxxxxxxx/T/ > [2]: https://lore.kernel.org/linux-spi/E81F4810-48DD-41EE-B110-D0D848B8A510@xxxxxxxxxxxxxxxx/T/ > [3]: https://lore.kernel.org/linux-spi/39DEC004-10A1-47EF-9D77-276188D2580C@xxxxxxxxxxxxxxxx/T/ > [4]: https://lore.kernel.org/linux-spi/20220525163946.48ea40c9@erd992/T/ I have a regression after this patch set. My system explodes with following trace: Unable to handle kernel paging request at virtual address 0064f69bfd319200 Mem abort info: ESR = 0x0000000086000004 EC = 0x21: IABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x04: level 0 translation fault [0064f69bfd319200] address between user and kernel address ranges Internal error: Oops: 0000000086000004 [#1] PREEMPT SMP Modules linked in: lan78xx etnaviv crct10dif_ce gpu_sched fsl_imx8_ddr_perf caam ina2xx ina3221 rtc_snvs error imx8mm_thermal imx_cpufreq_dt fuse CPU: 2 PID: 103 Comm: spi2 Tainted: G W 6.8.0-rc3-00118-g82b98fb8cd33 #36 Hardware name: Philips i.MX8MPlus Delta Evaluation Kit (DT) pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : 0x64f69bfd319200 lr : spi_res_release+0x68/0xb8 sp : ffff800083a6bcb0 x29: ffff800083a6bcb0 x28: ffff800081906008 x27: ffff8000809feea8 x26: 0000000000000001 x25: dead000000000122 x24: dead000000000100 x23: ffff800083c7ba38 x22: ffff0000c3ca5000 x21: ffff800083c7b9e0 x20: ffff800083c7ba40 x19: ffff800083c7bb48 x18: 0020000000000000 x17: 0000000000901400 x16: 00000000b0891400 x15: 049d200e412d4100 x14: 00000090fff6c1f4 x13: 000000280b412d41 x12: 000ed3ddde0a5202 x11: 6e0194029343039e x10: 00000000000014c0 x9 : ffff8000809fd5dc x8 : ffff800081906008 x7 : ffff0000c3c9c41c x6 : ffff8000800f34b0 x5 : 0000000000000000 x4 : ffff800083a6bab8 x3 : 8f64f69bfd319200 x2 : ffff800083c7bb60 x1 : ffff800083c7b9e0 x0 : ffff0000c3ca5000 Call trace: 0x64f69bfd319200 spi_async+0xac/0x110 9H0[]6 spi_mux_transfer_one_message+0xb8/0xf0 __spi_pump_transfer_message+0x26c/0x650 __spi_pump_messages+0xe0/0x228 spi_pump_messages+0x20/0x38 kthread_worker_fn+0xe0/0x2a8 kthread+0x10c/0x120 ret_from_fork+0x10/0x20 Code: ???????? ???????? ???????? ???????? (????????) ---[ end trace 0000000000000000 ]--- Kernel panic - not syncing: Oops: Fatal exception SMP: stopping secondary CPUs Kernel Offset: disabled CPU features: 0x0,00000008,00020000,2100421b Memory Limit: none Rebooting in 10 seconds.. It seems to be spi_mux specific. We have seen similar trace on other system with spi_mux. Regards, Oleksij -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
