On Fri, Jun 22, 2018 at 9:27 AM Fabio Estevam <festevam@xxxxxxxxx> wrote: > > Hi Andrey, > > On Thu, Jun 21, 2018 at 6:44 PM, Andrey Smirnov > <andrew.smirnov@xxxxxxxxx> wrote: > > > I just finished experimenting with it on RDU1 and Babbage boards and I > > can't reproduce the hang that you describe against 4.18-rc1. At this > > point I wonder if it's the bootloader that is a variable that plays > > into this. I was booting both boards with 2018.06.0 version of barebox > > + the custom patches that can be found here > > https://github.com/ndreys/barebox/commits/rdu1-netboot. Note that the > > last patch in that branch/stack was added as a part of this > > investigation, but even before it, I was able to boot Linux just fine, > > albeit without working USB. > > Thanks for investigating this issue. > > Yes, t is possible that the difference in behaviour that we see could > be related to the fact we use different bootloaders. > > In order to make things easier, I am sharing a Buildroot image for > imx51-babbage that contains U-Boot 2018.05 + kernel 4.17.2: > https://www.dropbox.com/s/yevnu4y1zdchnbt/sdcard.img?dl=0 > > Please flash it directly to the SD card via dd and boot it. > > You will notice that it will boot normally. Then please copy a > 4.18-rc1 zImage into the first SD card partition and you will notice > the hang. > It's definitely the bootloader, or more specifically whether or not it initialized/used USB before booting the kernel. Some interesting highlights: - On your "good" 4.17.2 based image, if you interrupt U-Boot, do "usb start" (optionally "usb stop") and then "boot", you'll get the hang that I was trying to fix with my patch. - Things are exact opposite with 4.18-rc1 and doing the above would _prevent_ the hang and the image would boot fine. - Disabling USB in Barebox based boot "stack" gets it to behave the same way as U-boot from your image (hanging when booting 4.18-rc1) Digging more into code it seems that the reason for 4.18-rc1's behavior is the fact that it's missing a call hw_phymode_configure() after usb_phy_init() and, AFAICT, the only reason it is not happening is because default image is being built without CONFIG_USB_CHIPIDEA_ULPI and CONFIG_USB_ULPI_BUS. Enabling those two options on 4.18-rc1, seem to fix the problem on both your U-Boot based image and my "special" Barebox setup. So AFAICT, this patch still fixes a valid issue (my use-case was net booting via USB-Ethernet dongle), but an additional patch enabling those two configuration options might be needed. Thoughts? Also, I don't have any i.MX53 HW, so I wasn't able to test the effects of enabling those two options there. Thanks, Andrey Smirnov -- 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
