Re: [Cbe-oss-dev] [PATCH 4/10] spidernet: zero out a pointer.
On Thu, May 17, 2007 at 09:32:56AM +1000, Michael Ellerman wrote: + hwdescr-buf_addr = 0x0; If you're going to be paranoid, shouldn't you do something here to make sure the value's hit the device? I thought the whole point of paranoia is that its inexplicable. Here's a delusional reply: I didn't see any point to it. 1) a wmb would add overhead 2) the hardware is supposed to be looking at the status flag, anyway, and not misbehaving. 3) there is a wmb when the descr is actually refilled in such a way as to actually mean something to the hardware. All that I really acomplished here is a minor trick to aid in debug printing when looking for something bad. --linas - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [Cbe-oss-dev] [PATCH 4/10] spidernet: zero out a pointer.
If you're going to be paranoid, shouldn't you do something here to make sure the value's hit the device? I thought the whole point of paranoia is that its inexplicable. Here's a delusional reply: I didn't see any point to it. 1) a wmb would add overhead A wmb() doesn't guarantee the write has reached the device. 2) the hardware is supposed to be looking at the status flag, anyway, and not misbehaving. But you're paranoid, right? Can't trust that device! :-) Segher - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [Cbe-oss-dev] [PATCH 4/10] spidernet: zero out a pointer.
Here's a delusional reply: I didn't see any point to it. 1) a wmb would add overhead 2) the hardware is supposed to be looking at the status flag, anyway, and not misbehaving. 3) there is a wmb when the descr is actually refilled in such a way as to actually mean something to the hardware. All that I really acomplished here is a minor trick to aid in debug printing when looking for something bad. And the whole thing is moot because 0 is actually a perfectly valid DMA address :-) I suspect spider will end up trying to hit some internal register or it's PCIe or whatever it has mapped at 0 internally and will blow up ... At least on spider, it's not RAM there Ben. - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [Cbe-oss-dev] [PATCH 4/10] spidernet: zero out a pointer.
On Wed, 2007-05-16 at 17:09 -0500, Linas Vepstas wrote: Invalidate a pointer as its pci_unmap'ed; this is a bit of paranoia to make sure hardware doesn't continue trying to DMA to it. Signed-off-by: Linas Vepstas [EMAIL PROTECTED] drivers/net/spider_net.c |7 +-- 1 file changed, 5 insertions(+), 2 deletions(-) Index: linux-2.6.22-rc1/drivers/net/spider_net.c === --- linux-2.6.22-rc1.orig/drivers/net/spider_net.c2007-05-15 13:31:11.0 -0500 +++ linux-2.6.22-rc1/drivers/net/spider_net.c 2007-05-15 13:31:16.0 -0500 @@ -1081,7 +1082,9 @@ spider_net_decode_one_descr(struct spide chain-tail = descr-next; /* unmap descriptor */ - pci_unmap_single(card-pdev, hwdescr-buf_addr, + hw_buf_addr = hwdescr-buf_addr; + hwdescr-buf_addr = 0x0; If you're going to be paranoid, shouldn't you do something here to make sure the value's hit the device? + pci_unmap_single(card-pdev, hw_buf_addr, SPIDER_NET_MAX_FRAME, PCI_DMA_FROMDEVICE); cheers -- Michael Ellerman OzLabs, IBM Australia Development Lab wwweb: http://michael.ellerman.id.au phone: +61 2 6212 1183 (tie line 70 21183) We do not inherit the earth from our ancestors, we borrow it from our children. - S.M.A.R.T Person signature.asc Description: This is a digitally signed message part
