On 21-03-23, 10:26, Bard Liao wrote: > From: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx> > > The existing code copies the hw_params pointer and reuses it later in > .prepare, specifically to re-initialize the ALH DMA channel > information that's lost in suspend-resume cycles. > > This is not needed, we can directly access the information from the > substream/rtd - as done for the HDAudio DAIs in > sound/soc/sof/intel/hda-dai.c > > In addition, using the saved pointer causes the suspend-resume test > cases to fail on specific platforms, depending on which version of GCC > is used. Péter Ujfalusi and I have spent long hours to root-cause this > problem that was reported by the Intel CI first with 6.2-rc1 and again > v6.3-rc1. In the latter case we were lucky that the problem was 100% > reproducible on local test devices, and found out that adding a > dev_dbg() or adding a call to usleep_range() just before accessing the > saved pointer "fixed" the issue. With errors appearing just by > changing the compiler version or minor changes in the code generated, > clearly we have a memory management Heisenbug. > > The root-cause seems to be that the hw_params pointer is not > persistent. The soc-pcm code allocates the hw_params structure on the > stack, and passes it to the BE dailink hw_params and DAIs > hw_params. Saving such a pointer and reusing it later during the > .prepare stage cannot possibly work reliably, it's broken-by-design > since v5.10. It's astonishing that the problem was not seen earlier. > > This simple fix will have to be back-ported to -stable, due to changes > to avoid the use of the get/set_dmadata routines this patch will only > apply on kernels older than v6.1. Applied, thanks -- ~Vinod
