On Friday, July 12, 2013 6:46 AM, Julius Werner wrote: > > Hi Jingoo, > > Yeah, I followed that discussion back then, but it seems to have > stalled a little (at least the HSIC patches haven't been picked up in > any kernel.org repo yet to my knowledge). > > The problem is that I think these approaches cannot work reliably. I > agree that it would be nice to control the HSIC device from its own > driver, and have spent quite some time playing around with the > usb/misc/usb3503.c driver to try to make this work... but there's a > timing dependency here that you just can't model correctly with > independent drivers. > > If the HSIC device is already active during boot (e.g. because it was > used by firmware), there's always a chance that the USB stack will > come up before the driver that resets it does. The device will be > enumerated as normal, and when the other driver later pulls the reset > signal the USB stack will not notice because there is no real > disconnect detection on HSIC. Only when you eventually try to send > another transfer to the device will you start to get timeouts, and the > newly reset device will not be able to reenumerate because the host > never asks it to. > > I really don't see how you could solve this without putting some kind > of synchronization mechanism in the USB drivers. So this leaves > ehci-s5p and phy-samsung-usb2 as the only possible places, and I chose > the latter since all the host-side HSIC initialization is also there > already. I think if you think of it as "reset whatever is on the other > side of this PHY", it's okay to put it as an optional feature into the > PHY driver. CC'ed Tomasz Figa, Dongjin Kim, Yulgon Kim Hi Tomasz, Dongjin, Julius Werner wants to put 'SMSC 3503 hub reset on Arndale board' to 'phy-samsung-usb*.c' files, because there is a timing dependency above mentioned. The following is the original patch sent by Julius Werner two day ago. (http://www.spinics.net/lists/linux-samsung-soc/msg20250.html) Previously, Olof mentioned that 'drivers/platform/arm/' would be used. (http://patches.linaro.org/16856/) Also, another way was mentioned by Fabio Estevam, using 'drivers/reset/gpio-reset.c' which is not merged yet. (http://permalink.gmane.org/gmane.linux.drivers.devicetree/36830) I think that 'phy-samsung-usb*.c' files are not a good place. However, Julius Werner's comment looks reasonable enough. If you have a comment, please feel free to share it. :) Thank you. Best regards, Jingoo Han -- 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
