On Wed, Aug 12, 2009 at 1:32 PM, Luis R. Rodriguez<lrodriguez@xxxxxxxxxxx> wrote: >>> diff --git a/drivers/net/wireless/ath/ath5k/base.c b/drivers/net/wireless/ath/ath5k/base.c >>> index 63c2b57..2b3cf39 100644 >>> --- a/drivers/net/wireless/ath/ath5k/base.c >>> +++ b/drivers/net/wireless/ath/ath5k/base.c >>> @@ -471,7 +471,7 @@ ath5k_pci_probe(struct pci_dev *pdev, >>> * DMA to work so force a reasonable value here if it >>> * comes up zero. >>> */ >>> - csz = L1_CACHE_BYTES / sizeof(u32); >>> + csz = L1_CACHE_BYTES >> 2; >>> pci_write_config_byte(pdev, PCI_CACHE_LINE_SIZE, csz); >> >> I'm not sure it's better, > > I did this for consistency between drivers but yes the advantage with > a shift is it should be cheaper than a multiplication. Although I am > not sure if simple multiplications get optimized by either the > compiler or an architecture to shifts. It shouldn't matter in the above case -- division by two constants. In the multiplication by power of 2 constant case, it should also get optimized by the compiler. '>> 2' looks like magic though, maybe a comment to say why? >> although the whole thing seems bogus to >> me. Is there really a modern machine where PCI cache line size should >> only be four bytes? To correct above, I misread what it was doing.. it's getting cpu cache size and dividing by 4 to get the number of words, if cache line size was zeroed initially. Ok, I'll go back to sleep now. Whether needed or not, there's a lot of confusing comments and voodoo around the stuff (something about 2.4 kernels...) that would be nice to clear up. > Whether we remove this though would be a change which should go > through a separate patch I think. Yeah, that's reasonable. -- Bob Copeland %% www.bobcopeland.com -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
