Tiny210 USB Camera 自动断开
现象：
使用usb camera 在lcd上显示图像时，偶尔发生USB ROOT HUB reset， 导致camera停止工作，
然后发生usb camera自动断开，然后又重新识别，断开又识别。
如果不使用usb camera，就不会发生 usb reset。
分析：
1、怀疑USB供电问题，导致usb不稳定，但是，使用带外接电源的usb，没有任何改善；
2、分析log，是usb异常中断导致，但是仍然无法判断异常的来源；
3、怀疑是驱动问题，更换linux 内核版本，3.4.2、3.7、3.9.7、3.10、3.13几个版本都有同样问题；
4、使用官方kernel 3.0.8就没有问题，确认还是驱动配置问题。但是仍然找不到原因。
使用排除法，移植3.0.8内核，一步一步添加官方驱动，无论与camera usb相关不相关，都要测试。
最终发现问题在LCD的GPIO配置上。
结果：
从Linux主线下载的新版本的kernel后，配置好LCD的时序，发生lcd能够正常工作，所以就没有继续关系LCD的配置，
尤其是 RGB的GPIO配置，甚至都没有把LCD的GPIO配置成功能引脚，但恰巧是这方面的问题。
最终重新配置LCD的gpio 为功能，并设置驱动能力， 经过很长时间的测试USB没有发生reset。
问题log：
[liujia@210]#[ 171.257109] lj:port 1, status 0100, change 0001, 12 Mb/s [ 171.257174] usb 1-1: USB disconnect, device number 23 [ 171.257219] usb 1-1.2: USB disconnect, device number 24 [ 171.522012] usb 1-1: new high-speed USB device number 25 using s5p-ehci [ 171.652422] usb 1-1: New USB device found, idVendor=0424, idProduct=2514 [ 171.652480] usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0 [ 171.657089] hub 1-1:1.0: USB hub found [ 171.657294] hub 1-1:1.0: 4 ports detected [ 171.857405] lj:port 2, status 0101, change 0000, 12 Mb/s [ 171.942257] usb 1-1.2: new high-speed USB device number 26 using s5p-ehci [ 172.265034] usb 1-1.2: New USB device found, idVendor=046d, idProduct=0825 [ 172.265093] usb 1-1.2: New USB device strings: Mfr=0, Product=0, SerialNumber=2 [ 172.265154] usb 1-1.2: SerialNumber: F46BE640 [ 172.269636] uvcvideo: Found UVC 1.00 device <unnamed> (046d:0825) [ 172.291195] input: UVC Camera (046d:0825) as /devices/platform/s5p-ehci/usb1/1-1/1-1.2/1-1.2:1.0/input/input10 [ 174.309219] lj:port 1, status 0100, change 0001, 12 Mb/s [ 174.309283] usb 1-1: USB disconnect, device number 25 [ 174.309328] usb 1-1.2: USB disconnect, device number 26 [ 174.572011] usb 1-1: new high-speed USB device number 27 using s5p-ehci [ 174.702413] usb 1-1: New USB device found, idVendor=0424, idProduct=2514 [ 174.702471] usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0 [ 174.706912] hub 1-1:1.0: USB hub found [ 174.707163] hub 1-1:1.0: 4 ports detected [ 174.907402] lj:port 2, status 0101, change 0000, 12 Mb/s [ 174.992252] usb 1-1.2: new high-speed USB device number 28 using s5p-ehci [ 175.315403] usb 1-1.2: New USB device found, idVendor=046d, idProduct=0825 [ 175.315462] usb 1-1.2: New USB device strings: Mfr=0, Product=0, SerialNumber=2 [ 175.315524] usb 1-1.2: SerialNumber: F46BE640 [ 175.320003] uvcvideo: Found UVC 1.00 device <unnamed> (046d:0825) [ 175.341248] input: UVC Camera (046d:0825) as /devices/platform/s5p-ehci/usb1/1-1/1-1.2/1-1.2:1.0/input/input11 [ 183.131082] lj:port 1, status 0100, change 0001, 12 Mb/s [ 183.131146] usb 1-1: USB disconnect, device number 27 [ 183.131191] usb 1-1.2: USB disconnect, device number 28 [ 183.397012] usb 1-1: new high-speed USB device number 29 using s5p-ehci [ 183.527401] usb 1-1: New USB device found, idVendor=0424, idProduct=2514 [ 183.527458] usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0 [ 183.531947] hub 1-1:1.0: USB hub found [ 183.532271] hub 1-1:1.0: 4 ports detected [ 183.732386] lj:port 2, status 0101, change 0000, 12 Mb/s [ 183.817231] usb 1-1.2: new high-speed USB device number 30 using s5p-ehci [ 184.140261] usb 1-1.2: New USB device found, idVendor=046d, idProduct=0825 [ 184.140320] usb 1-1.2: New USB device strings: Mfr=0, Product=0, SerialNumber=2 [ 184.140382] usb 1-1.2: SerialNumber: F46BE640 [ 184.144692] uvcvideo: Found UVC 1.00 device <unnamed> (046d:0825) [ 184.166384] input: UVC Camera (046d:0825) as /devices/platform/s5p-ehci/usb1/1-1/1-1.2/1-1.2:1.0/input/input12
解决patch：
static void s5pv210_fb_cfg_gpios(unsigned int base, unsigned int nr)
{
s3c_gpio_cfgrange_nopull(base, nr, S3C_GPIO_SFN(2));
for (; nr > 0; nr--, base++)
s5p_gpio_set_drvstr(base, S5P_GPIO_DRVSTR_LV4);
}
void s5pv210_fb_gpio_setup_24bpp(void)
{
#if 0
s5pv210_fb_cfg_gpios(S5PV210_GPF0(0), 8);
s5pv210_fb_cfg_gpios(S5PV210_GPF1(0), 8);
s5pv210_fb_cfg_gpios(S5PV210_GPF2(0), 8);
s5pv210_fb_cfg_gpios(S5PV210_GPF3(0), 4);
/* Set DISPLAY_CONTROL register for Display path selection.
*
* ouput | RGB | I80 | ITU
* -----------------------------------
* 00 | MIE | FIMD | FIMD
* 01 | MDNIE | MDNIE | FIMD
* 10 | FIMD | FIMD | FIMD
* 11 | FIMD | FIMD | FIMD
*/
writel(0x2, S5P_MDNIE_SEL);
#endif
int i;
for (i = 0; i < 8; i++) {
s3c_gpio_cfgpin(S5PV210_GPF0(i), S3C_GPIO_SFN(2));
s3c_gpio_setpull(S5PV210_GPF0(i), S3C_GPIO_PULL_NONE);
}
for (i = 0; i < 8; i++) {
s3c_gpio_cfgpin(S5PV210_GPF1(i), S3C_GPIO_SFN(2));
s3c_gpio_setpull(S5PV210_GPF1(i), S3C_GPIO_PULL_NONE);
}
for (i = 0; i < 8; i++) {
s3c_gpio_cfgpin(S5PV210_GPF2(i), S3C_GPIO_SFN(2));
s3c_gpio_setpull(S5PV210_GPF2(i), S3C_GPIO_PULL_NONE);
}
for (i = 0; i < 4; i++) {
s3c_gpio_cfgpin(S5PV210_GPF3(i), S3C_GPIO_SFN(2));
s3c_gpio_setpull(S5PV210_GPF3(i), S3C_GPIO_PULL_NONE);
}
/* mDNIe SEL: why we shall write 0x2 ? */
writel(0x2, S5P_MDNIE_SEL);
/* drive strength to 2x ....(max for smdkv210) */
writel(0xaaaaaaaa, S5PV210_GPF0_BASE + 0xc);
writel(0xaaaaaaaa, S5PV210_GPF1_BASE + 0xc);
writel(0xaaaaaaaa, S5PV210_GPF2_BASE + 0xc);
writel(0x000000aa, S5PV210_GPF3_BASE + 0xc);
}