I am running into an odd intermittent symptom using the Samsung S3C2410 ARM SOC with the 2.6.14.3 kernel (it seems to happen occasionally, but less often, with the 2.6.10 kernel). This chip has built-in OHCI, which has virtually no documentation in the manual except for the addresses of the OHCI controller registers. The gross symptom is that intermittently (say, 50% of the time in the worst configuration of U-Boot and kernel versions) none of the USB devices get enumerated (i.e., lsusb only sees the root hub); this appears to be due to an -ETIMEDOUT error trying to read a descriptor. A more detailed symptom (based on turning on both CONFIG_USB_DEBUG and OHCI_VERBOSE_DEBUG on ohci-hcd.c, and adding some additional ohci_dbg() messages) is that (consistently) in the cases that successfully enumerate devices, the controller is sending SOF's (based on the SF bit in the InterruptStatus register) pretty much as soon as OHCI_USB_OPER is written to HcControl in ohci_run(), whereas in the unsuccessful cases, SF only starts appearing later on (after some more register accesses). The former behavior appears to be correct based on documentation of the HCFS field in the OHCI spec.
1) ohci-hcd.c often reads() a register after writing it to "flush" the write. Is there a rule about this, and where does it come from? (In fact, the OHCI_USB_OPER write does not have such a flush, but the behavior doesn't change when you add one). 2) Are there any errata or quirks for the OHCI controller on the S3C2410? (I tried unsuccessfully to register on the Samsung site in case there was more info.) 3) Does this suggest anything to anyone? Is the micro-symptom plausibly connected to the gross, non-enumeration symptom? Thanks for any assistance, Steve ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_id=7637&alloc_id=16865&op=click _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
