Hi Russ, On Sunday 10 February 2008 03:32, Russell McGuire wrote: > All, > > So I am in the process of debugging my newly established HDLC driver. > More or less modeled after a simplified gianfar / ucc_geth idea. > > However, after loading, etc. and using the following commands > > -> insmod hdlc-8360.ko > -> sethdlc hdlc0 hdlc-eth > -> ifconfig hdlc0 up 192.168.1.100 > > All is well, and I am seeing IDL interrupts. Great. > > Now I go to ping an address like, > ping 192.168.1.101 > > I can see that I get the start_xmit function, the IRQ from the QE comes > back and reports the TXBD as successfully sent. > > Here is the problem, when I goto free the skb in the tx_handler, I get a > 'Unable to Handle Kernel Paging Request for data at address 0x00000000' > Even though for the life of me, I can't see any pointers that are at > address zero.
I'm experiencing a similar problem here with a in-house HDLC driver. The kernel oopses after some time under high HDLC loads. Could you please post a backtrace to see if our problems are related ? How do you free the skb ? Posting code snippet (or even the whole source code) would help. > I have checked the pointer value I am passing in, and indeed it is the > exact same pointer I am receiving from the original > start-xmit call.. > > Are we supposed to copy the skb? And free it immediately in the start_xmit? > Some special way to store the pointer? My understanding is that the skb is supposed to be freed in the TX interrupt handler. > I have tried > txbd->buf = skb->data; > txbd->buf = virt_to_phys(skb->data); > etc.. and various other ways to save that I have seen in the gianfar and > ucc_geth drivers. You should map the skb data buffer using dma_map_single. Don't forget to unmap it with dma_unmap_single in the TX interrupt handler. > My tx_sk_buff** is identical as alloced the same way. > > Anyone have any ideas? Best regards, -- Laurent Pinchart CSE Semaphore Belgium Chaussée de Bruxelles, 732A B-1410 Waterloo Belgium T +32 (2) 387 42 59 F +32 (2) 387 42 75
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