On Fri, 2018-03-23 at 07:41 -0500, Jared Bents wrote: > Thank you for the advice. Looks like I get to try to rewrite the ath9k and > ath10k drivers to use dma_alloc_coherent() instead of kmemdup() and > dev_alloc_skb()
Euh no... dev_alloc_skb() is the right thing to do for receive packets for a device driver. The arch should be able to map that for DMA, even if include bounce buffers via swiotlb. Cheers, Ben. > On Thu, Mar 22, 2018 at 8:19 PM, Oliver <ooh...@gmail.com> wrote: > > On Fri, Mar 23, 2018 at 1:37 AM, Jared Bents > > <jared.be...@rockwellcollins.com> wrote: > > > Thank you for the response but unfortunately, it looks like I already > > > have that and it is being used. To verify, I commented that out and > > > got the failure "dma_direct_alloc_coherent: No suitable zone for pfn > > > 0xe0000". Below is the code flow for function > > > ath10k_pci_hif_exchange_bmi_msg which is showing the first dma mapping > > > error. > > > > > > ath10k_pci_hif_exchange_bmi_msg -> dma_map_single -> > > > dma_map_single_attrs -> swiotlb_map_page -> dma_capable (returns > > > false) > > > > > > > > > dma_capable is what reports the failure in that flow. > > > > > > static inline bool dma_capable(struct device *dev, dma_addr_t addr, > > > size_t size) > > > { > > > #ifdef CONFIG_SWIOTLB > > > struct dev_archdata *sd = &dev->archdata; > > > > > > if (sd->max_direct_dma_addr && addr + size > sd->max_direct_dma_addr) > > > return false; > > > #endif > > > > > > if (!dev->dma_mask) > > > return false; > > > > > > return addr + size - 1 <= *dev->dma_mask; > > > } > > > Getting the below values: > > > addr = 1ee376218 > > > size = 4 > > > sd->max_direct_dma_addr = e0000000 which is I believe DMA window size > > > (e0000000) > > > > > > when executed sd->max_direct_dma_addr(e0000000) && addr(1ee376218) + > > > size(4) becomes e0000004 which is > sd->max_direct_dma_addr (e0000000) > > > > > > > > > So even though limit_zone_pfn(ZONE_DMA32, 1UL << (31 - PAGE_SHIFT)) is > > > being used in arch/powerpc/platforms/85xx/corenet_generic.c, > > > > > kmemdup(req, req_len, GFP_KERNEL) is returning an address that when > > > sent to dma_map_single(), results in a bad map. > > > > You need to use (GFP_KERNEL | GFP_DMA32) to constrain the allocations > > to ZONE_DMA32. Without that the kmemdup() will allocate from any zone > > so you'll probably get an unmappable address. > > > > That said, the driver probably shouldn't be using kmemdup() here. > > DMA-API.txt pretty explicitly says that drivers should not assume that > > dma_map_single() will work with arbitrary memory. It should be using > > dma_alloc_coherent() or a dma pool here. > > > > > - Jared > > > > > > On Wed, Mar 21, 2018 at 11:54 PM, Oliver <ooh...@gmail.com> wrote: > > >> On Thu, Mar 22, 2018 at 8:00 AM, Jared Bents > > >> <jared.be...@rockwellcollins.com> wrote: > > >>> 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. > > >> > > >> I think there's a known issue with the freescale PCIe root complex > > >> where it can't DMA beyond the 4GB mark. There's a workaround in > > >> the form of limit_zone_pfn() which you can use to put the lower 4GB into > > >> ZONE_DMA32 and allocate from there rather than ZONE_NORMAL. > > >> For details of how to use it have a look at corenet_gen_setup_arch() in > > >> arch/powerpc/platforms/85xx/corenet_generic.c > > >> > > >> Hope that helps, > > >> Oliver > >