imx6: PCIe imx6_pcie_assert_core_reset() hangs after watchdog reset

Tim Harvey tharvey at
Thu Mar 26 06:23:55 PDT 2015

On Thu, Mar 26, 2015 at 4:06 AM, Lucas Stach <l.stach at> wrote:
> Am Mittwoch, den 25.03.2015, 11:32 +0100 schrieb Stefan Roese:
> Okay, I've looked a bit into this and it seems there is no easy solution
> available. It is really unfortunate that the WD reset doesn't reset the
> GPR registers. Also I have no idea if the WD reset properly resets the
> PCIe core, as the reset signal of this core is only wired to the POR
> line.
> To fix this (almost) properly we would have to change the complete init
> order of the core, which isn't an easy task, as experience has shown
> that even small changes in that area can prevent the link from coming up
> under certain circumstances.
> Which brings me back to my earlier assertion that WD reset should really
> be done through the PMIC. That's yet another case of a WD making the
> overall system more instable.
> I think the easiest workaround for now is to detect the WD reset in your
> bootloader and bash the expected default values into the GPR bits.
> Regards,
> Lucas


There are many boards out there that unfortunately don't reset PMIC's
properly, IMHO due to a confusing reference design from Freescale.

Using the WDOGx_WRSR register we can detect the reason for reset:
 Bit 4 - POR - Power on reset
 Bit 1 - TOUT - Watchdog timeout
 Bit 0 - SFTW - Software reset (used in machine_restart)

Can we reset the GPR registers based on bits 0 or 1 set, or use these
as further qualifiers in the WAR?


More information about the linux-arm-kernel mailing list