FSL/NXP P5020: USB problems with the latest Git kernels

Laurentiu Tudor laurentiu.tudor at nxp.com
Thu Sep 6 00:08:21 AEST 2018


Hi Scott,

> -----Original Message----- 
> On Mon, 2018-08-27 at 20:15 +0200, Christian Zigotzky wrote:
> > Hello,
> >
> > Our users tested the RC1 of kernel 4.19 on their P5020 boards today.
> > Unfortunately the USB bug still exists. With mem values bigger than
> 4096M,
> > the USB mouse and keyboard doesn’t work. With the bootarg mem=4096M, the
> USB
> > devices work without any problems. Please compile the RC1 and test it on
> > your P5020 board. There is a problem with the memory management since
> > 22/08/18.
> 
> I just tested 4.19-rc1 on a T4240 and got a similar problem with MMC.  MMC
> and
> USB on these chips both have a 32-bit DMA limitation.  I'll look into it.

I encountered similar issues on LS104xA chips. This is the workaround for MMC:
https://patchwork.kernel.org/patch/10506627/
On the USB side I didn't find a proper place in the usb subsystem code for a workaround but instead
found an undocumented kernel arg (*) that limits the dma mask to 32 bits:
xhci-hcd.quirks=0x800000.

(*) https://patchwork.kernel.org/patch/10509159/

---
Best Regards, Laurentiu


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