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) adam > Thank you. > > -- > Regards, > > Laurent Pinchart > > -- > 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 -- 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
