Re: [PATCH v3 0/3] Revised Renesas uPD72020x workaround for 32bit DMA issue

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On Wed, May 23, 2018 at 06:41:35PM +0100, Marc Zyngier wrote:
> Back around the 4.13 timeframe, we tried to address a rather bad issue
> with the Renesas uPD72020x USB3 controller family. They have trouble
> with the programming of the base addresses which tend to stick on XHCI
> reset. This makes transitionning from 64bit to 32bit addresses
> completely unsafe. This was observed on a fairly popular arm64
> platform (AMD Opteron 1100, which has all of its memory above 4GB).
> 
> The fix was to perform a PCI reset of the device, but we have had
> multiple reports that this generated regressions (the controller not
> being usable after the patch was applied).
> 
> This series reverts the problematic patch, and tries to address it in
> a more constrained way. If the controller is behind an IOMMU (and only
> in that case), we zero its base addresses before reseting it. In the
> affected configuration, this has the effect of putting the device in a
> state where the XHCI reset will be effective.
> 
> It must be noted that in the absence of an IOMMU (and maybe even in
> its presence), this device is completely unsafe, and may silently
> corrupt memory.

Mathias, any objections for me queueing these up now for 4.18-rc1?

thanks,

greg k-h
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