一步一步解决 kernel 26 usb host driver.docVIP

一步一步解决 kernel 2.6 usb host driver (以下讨论基于kernel 2.6.11，ARM9 s3c2410，arm-linux-gcc 3.4.1 ) ================================================= 2.6在s3c2410上usb host不工作的直接结果就是提示110错误： usb 1-1: device descriptor read/64, error -110 追踪错误代码，我们来看看能不能找到导致这个错误的线索。 include/asm-generic/errno.h #define EPROTO 71 /* Protocol error */ #define EILSEQ 84 /* Illegal byte sequence */ #define ETIMEDOUT 110 /* Connection timed out */ Documentation/usb/error-codes.txt -EPROTO (*, **) a) bitstuff error b) no response packet received within the prescribed bus turn-around time c) unknown USB error -EILSEQ (*, **) a) CRC mismatch b) no response packet received within the prescribed bus turn-around time c) unknown USB error -ETIMEDOUT (**) No response packet received within the prescribed bus turn-around time. This error may instead be reported as -EPROTO or -EILSEQ. 由此我们可以判断，这个错误与 usb 设备的超时有关。报告这个错误的地方在drivers/usb/core/hub.c中的hub_port_init部分，由于usb_get_device_descriptor获取 usb 设备信息的时候产生了超时。这样基本可以确定三种情况，1、usb 设备及接口有问题；2、usb core有问题；3、usb driver有问题。 我们可以很容易地排除1和2的可能性，问题应该在usb driver implement部分造成的。2.6的usb driver把usb规范中对usb接口的操作集中到了core里面，针对不同设备的implement分别归为host、gadget、storage等。基本确定问题就在ohci-s3c2410.c里。 跟踪进入ohci-s3c2410.c，这里面主要完成s3c2410 usb host设备的初始化工作，包括电源、时钟、寄存器等。 其实很多问题在互联网上已经被遇到和解决，我们要做的就是多参考别人的成功经验，这样可以节省时间，同时能够帮助我们找到一些思路。借助google这双强大的翅膀，我们来看看能找到什么： /FAQ.html#ts6 Q: Why doesn’t USB work at all? I get “device not accepting address”. A: You may have some problem with your PCI setup that’s preventing your USB host controller from getting hardware interrupts. When Linux submits a request, but never hears back from the controller, this is the diagnostic you’ll see. To see if this is the problem, look at /proc/interrupts to see if the interrupt count for your host controller driver ever goes up. If it doesn’t, this is the problem: either your BIOS isn’t telling the truth to Linux (ACPI sometimes confuses these things, or setting the expected OS to windows in your BIOS),