On 01/03, Adam Ford wrote: > On Thu, Dec 8, 2016 at 3:24 PM, Laurent Pinchart > <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > > Hi Stephen, > > > > On Thursday 08 Dec 2016 13:16:01 Stephen Boyd wrote: > >> On 12/02, Laurent Pinchart wrote: > >> > From: Richard Watts <rrw@xxxxxxxxxxxxx> > >> > > >> > The OMAP36xx DPLL5, driving EHCI USB, can be subject to a long-term > >> > frequency drift. The frequency drift magnitude depends on the VCO update > >> > rate, which is inversely proportional to the PLL divider. The kernel > >> > DPLL configuration code results in a high value for the divider, leading > >> > to a long term drift high enough to cause USB transmission errors. In > >> > the worst case the USB PHY's ULPI interface can stop responding, > >> > breaking USB operation completely. This manifests itself on the > >> > Beagleboard xM by the LAN9514 reporting 'Cannot enable port 2. Maybe the > >> > cable is bad?' in the kernel log. > >> > > >> > Errata sprz319 advisory 2.1 documents PLL values that minimize the > >> > drift. Use them automatically when DPLL5 is used for USB operation, > >> > which we detect based on the requested clock rate. The clock framework > >> > will still compute the PLL parameters and resulting rate as usual, but > >> > the PLL M and N values will then be overridden. This can result in the > >> > effective clock rate being slightly different than the rate cached by > >> > the clock framework, but won't cause any adverse effect to USB > >> > operation. > >> > > >> > Signed-off-by: Richard Watts <rrw@xxxxxxxxxxxxx> > >> > [Upported from v3.2 to v4.9] > >> > Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> > >> > --- > >> > >> Applied to clk-next > > > > Since this fixes an errata issue, is there any way we can get this > patch applied to the older LTS kernels? (4.4 seems to apply cleanly, > but I didn't try any older than that) > Sure. Just follow the stable kernel rules. See Documentation/process/stable-kernel-rules.rst, specifically option #2. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project -- 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
