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It was only for diagnostic purposes, >>>>>>>> i.e. to see if there is some kind of cache coherence issue, >>>>>>>> which seems to be the case? So perhaps the only fix needed is >>>>>>>> to add dma-coherent to our device tree? >>>>>>> >>>>>>> That sounds quite error prone. How many other DT blobs are >>>>>>> missing the property? If the memory should be coherent, i would >>>>>>> expect the driver to allocate coherent memory. Or the driver >>>>>>> needs to handle non-coherent memory and add the necessary >>>>>>> flush/invalidates etc. >>>>>> >>>>>> stmmac driver does the necessary cache flush/invalidates to >>>>>> maintain cache lines explicitly. >>>>> >>>>> Given the problem happens when the kernel performs syncing, is it >>>>> possible that there is a problem with how the syncing is performed? >>>>> >>>>> I am not familiar with this driver, but it seems to allocate multiple >>>>> buffers per packet when split header is enabled and these buffers are >>>>> allocated from the same page pool (see stmmac_init_rx_buffers()). >>>>> Despite that, the driver is creating the page pool with a non-zero >>>>> offset (see __alloc_dma_rx_desc_resources()) to avoid syncing the >>>>> headroom, which is only present in the head buffer. >>>>> >>>>> I asked Thierry to test the following patch [1] and initial testing >>>>> seems OK. He also confirmed that "SPH feature enabled" shows up in the >>>>> kernel log. >>>> >>>> It is recommended to disable the "SPH feature" by default unless some >>>> certain cases depend on it. Like Ido said, two large buffers being >>>> allocated from the same page pool for each packet, this is a huge waste >>>> of memory, and brings performance drops for most of general cases. >>>> >>>> Our downstream driver and two mainline drivers disable SPH by default: >>>> https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/tree/drivers/net/ethernet/stmicro/stmmac/dwmac-dwc-qos-eth.c#n357 >>>> https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/tree/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c#n471 >>> >>> Okay, that's something we can look into changing. What would be an >>> example of a use-case depending on SPH? Also, isn't this something >>> that should be a policy that users can configure? >>> >>> Irrespective of that we should fix the problems we are seeing with >>> SPH enabled. >> >> >> Any update on this? > > Sorry for my late response, I was on Chinese New Year holiday. No problem! Happy new year! > The fix is sent, and it will be so nice to have your Tested-by: tag there: > https://lore.kernel.org/all/20250207085639.13580-1-0x1207@gmail.com/ Thanks, I have tested and responded. All looking good! Jon -- nvpublic