Hi all, Apologies for the amount of information but we've been debugging this for a while and I wanted to get what we are seeing captured as much as possible. We are a T1042 processor and have a total 8GB DDR and our kernel version is fsl-sdk-v2.0-1703 (linux v4.1.35) as that is the latest version supplied by NXP.
A while ago we ported from 32 bit to 64 bit. Everything continued to work except the ath10k module we have. So as a first step, we checked to see if an ath9k module also failed to work and it was also no longer working. The ath10k is working fine on a 32 bit system but it's not working on 64 bit system as we are getting dma mapping errors when trying to initialize the wifi modules. pci_bus 0002:01: bus scan returning with max=01 pci_bus 0002:01: busn_res: [bus 01] end is updated to 01 pci_bus 0002:00: bus scan returning with max=01 ath10k_pci 0000:01:00.0: unable to get target info from device ath10k_pci 0000:01:00.0: could not get target info (-5) ath10k_pci 0000:01:00.0: could not probe fw (-5) ath10k_pci 0001:01:00.0: Direct firmware load for ath10k/cal-pci-0001:01:00.0.bin failed with error -2 First, we have tried the mainline kernel (v4.15) to see if that would fix the issue, it did not. So I made a patch for the ath10k driver to restrict to just GFP_DMA areas when allocating memory or creating sk_buffs and have attached it. The ath10k wifi modules now initialize correctly but when I try to connect them and send traffic, they get a DMA mapping error from the sk_buff that it receives from elsewhere in the kernel. So while the driver appears to be fixable with the patch, the modules are still unusable due to data being sent to the driver when ath10k_tx is called and it tries to dma map with the provided skb. Also, according to the ath10k mailing list, GFP_DMA is not supposed to be used in general. The error below is the same sort of dma mapping error that is seen when initializing the modules without the patch to OR with GFP_DMA. ath10k_pci 0001:01:00.0: failed to transmit packet, dropping: -5 We asked on the ath10k mailing list if anyone else is having this problem and no one else seems to have the issue but they are using different architectures (ARM or X86). As a result, it does not seem to be a driver issue to us but something within the PowerPC arch. So we dug a little deeper to try to find what addresses being mapped are working and what address being mapped are not working. We found that when the virtual address of data pointer (a member of sk_buff) is above ~3.7 GB RAM address range then return address from dma_map_single API is failed to validate in dma_mapping_error function. We also noticed that in a 64bit machine sometimes ping is working and because of the virtual address is under ~3.7GAM RAM address range. So if we set mem=2048M in the bootargs, the ath10k module works perfectly, however this isn't a real solution since it cuts our available RAM from 8GB to 2GB. Any information that could help us resolve this issue would be greatly appreciated. Thank you, Jared
