On Thu, Dec 12, 2013 at 02:20:59AM +0200, Grazvydas Ignotas wrote: > This is a hard to reproduce problem which leads to non-functional > USB-OTG port in 0.1%-1% of all boots. Tracked it down to commit > e25bec160158abe86c "omap2+: save and restore OTG_INTERFSEL", > which introduces save/restore of OTG_INTERFSEL over suspend. > > Since the resume function is also called early in driver init, it uses a > non-initialized value (which is 0 and a non-supported setting in DM37xx > for INTERFSEL). Shortly after the correct value is set. Apparently this > works most time, but not always. > > Fix it by not writing the value on runtime resume if it is 0 > (0 should never be saved in the context as it's invalid value, > so we use it as an indicator that context hasn't been saved yet). > > This issue was originally found by Andreas Naumann: > http://marc.info/?l=linux-usb&m=138562574719654&w=2 > > Reported-and-bisected-by: Andreas Naumann <anaumann@xxxxxxxxxxxxxx> > Signed-off-by: Grazvydas Ignotas <notasas@xxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> > --- > This is a regression from 3.2, so should go to -rc and stable, IMO. > It's really annoying issue if you want to have a stable OTG behavior, > I've burned quite a lot of time on it myself over a year ago and gave up > eventually. Good thing Andreas finally found it, many thanks to him! > > drivers/usb/musb/omap2430.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/usb/musb/omap2430.c b/drivers/usb/musb/omap2430.c > index 2a408cd..737b3da 100644 > --- a/drivers/usb/musb/omap2430.c > +++ b/drivers/usb/musb/omap2430.c > @@ -672,7 +672,8 @@ static int omap2430_runtime_resume(struct device *dev) > > if (musb) { > omap2430_low_level_init(musb); > - musb_writel(musb->mregs, OTG_INTERFSEL, > + if (musb->context.otg_interfsel != 0) You might want to write an inline comment explaining why you're checking otg_interfsel for 0 here (as you explained 0 is not a valid value to be found). Br, David > + musb_writel(musb->mregs, OTG_INTERFSEL, > musb->context.otg_interfsel); > phy_power_on(musb->phy); > } > -- > 1.7.9.5 > > -- > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
