[RFC PATCH 1/9] usb: xhci: Add missing cache flush in the scratchpad array initialization

[Nicolas Saenz Julienne]

On Wed, 2020-04-22 at 17:21 +0800, Bin Meng wrote:
> Hi Nicolas,
> 
> On Wed, Apr 22, 2020 at 4:53 PM Nicolas Saenz Julienne
> <nsaenzjulienne at suse.de> wrote:
> > Hi Sylwester, Marek
> > 
> > On Tue, 2020-04-21 at 18:50 +0200, Sylwester Nawrocki wrote:
> > > In current code there is no cache flush after initializing the scratchpad
> > > buffer array with the scratchpad buffer pointers. This leads to a failure
> > > of the "slot enable" command on the rpi4 board (Broadcom STB PCIe
> > > controller + VL805 USB hub) - the very first TRB transfer on the command
> > > ring fails and there is a timeout while waiting for the command completion
> > > event. After adding the missing cache flush everything seems to be working
> > > as expected.
> > > 
> > > Signed-off-by: Sylwester Nawrocki <s.nawrocki at samsung.com>
> > > Reviewed-by: Bin Meng <bmeng.cn at gmail.com>
> > > ---
> > 
> > I've been trying to get this working on my own and got stuck with this
> > specific
> > issue. I'm glad you found a solution, it was driving me crazy.
> > 
> > Out of curiosity how did you found the solution?
> > 
> > >  drivers/usb/host/xhci-mem.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > > 
> > > diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
> > > index 93450ee..729bdc3 100644
> > > --- a/drivers/usb/host/xhci-mem.c
> > > +++ b/drivers/usb/host/xhci-mem.c
> > > @@ -393,6 +393,9 @@ static int xhci_scratchpad_alloc(struct xhci_ctrl
> > > *ctrl)
> > >               scratchpad->sp_array[i] = cpu_to_le64(ptr);
> > >       }
> > > 
> > > +     xhci_flush_cache((uintptr_t)scratchpad->sp_array,
> > > +                      sizeof(u64) * num_sp);
> > > +
> > 
> > Marek, souldn't running 'dcache off; icache off' be equivalent to this
> > (which
> > didn't do the trick for me)? or am I missing somthing?
> 
> I guess something is wrong with RPi4's "dcache off" command ..

You can't trust anything these times :)

I'll look into it.

Regards,
Nicolas

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