On Tue, Apr 13, 2010 at 1:48 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: >> I never saw the mass storage driver enqueue more sg entries than >> TRBS_PER_SEGMENT. It's just Ramya's driver that has this behavior. At >> this point, we can't tell what he's doing without his source code. > > This directly contradicts Ramya's statement above: "When I am testing > the default usb storage driver with 960 max_sectors Sarah saw ~120 > scatter-gather list entries." > > Evidently the two of you need to figure out exactly what happened. > More tests can't hurt... Sorry to confuse you but please find the scenario that resulted in the above discussion. Initially, I was working on a UASP driver and was seeing a timeout issue. So, during my debug process, I also tested the default mass storage driver by increasing the max sectors to 960, since our device is capable of supporting it. Here, I encountered a similar issue and sent my logs to Sarah, requesting her help. At that point, the logs had indicated that scatter gather list had 73 entries (>63). Later, I used the Sarah Sharp “xhci-large-tx” branch where TRBS_PER_SEGMENT is set to 128, which was thought about as a temporary fix. That is the reason I saw 120 scatter-gather list entries. However, today I tested the default usb storage driver for more than 10 times by setting the TRBS_PER_SEGEMENT to 64 and I am unable to see sg_list entries greater than 63. When I changed TRBS_PER_SEGMENT to 128 then I am seeing 120 sg_list entries. But, that still leaves my issue in the unresolved state, since I am unable to do large transfers consistently (with default mass storage driver) when max_sectors is set to 960. I tried the same with EHCI driver (using USB2.0 port) and it works fine without any issue. I aslo tried with USB 2.0 cable by connecting it to USB 3.0 port and it works fine without any issues. So, I guess it should either be a hardware issue or maybe something related to xHCI driver. I can send the latest logs, if needed. Thansk and Regards, Ramya. -- 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
