On 18/11/09 21:28, Alan Stern wrote: > If you don't have a good kernel to start from then there's nothing to > search for. I was assuming that a relatively recent kernel change > might have caused the slow-down, but if it has been this way for a long > time then a different approach is needed. The earliest kernel I've had this happen with is 2.6.28-rc2, when I first started using it with an OHCI controller. > There's no particular significance to 256 ms that I know of, although > if the hardware is malfunctioning it could easily pick such a rate. > The page size is significant because that's how the driver and the > hardware divide up transfers; each Transfer Descriptor refers to at > most 4096 bytes of data. > > On Wed, 18 Nov 2009, Simon Arlott wrote: >> The OHCI code appears to split the data up into 4096 chunks, but even the >> odd sized transfer of 25280 bytes at the end runs at the same speed: >> >> [ 4774.830569] cxacru: sending fw 0x3 size 0x62c0 to #98668 >> [ 4776.410375] cxacru: sending fw 0x3 size 0x100 to #e0 > > Yep. My intuition says "hardware problem", but there's no hard > evidence one way or another. > > What happens with other sorts of devices, such as a USB flash drive? On my desktop, I don't usually use the OHCI controller directly, but through hubs on EHCI. I do have an USB Audio device which works ok using OHCI. The firmware load fails over EHCI (via a hub) despite running even faster: [89633.219403] cxacru: sending fw 0x3 size 0x8000 to #7000 [89633.220147] cxacru: sending fw 0x3 size 0x8000 to #e000 [89633.220530] cxacru: sending fw 0x3 size 0x8000 to #15000 [89633.220774] cxacru: sending fw 0x3 size 0x8000 to #1c000 [89633.220898] cxacru: sending fw 0x3 size 0x8000 to #23000 [89633.221286] cxacru: sending fw 0x3 size 0x8000 to #2a000 338µs per 32KB... which is 775mbit/s+ and doesn't make sense. I can write a 10MB file to an USB flash drive over OHCI, and umount+sync takes around 13 seconds. -- Simon Arlott -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
