Re: [PATCH for-4.14 3/3] xen/arm: plat: Allocate as much as possible memory below 1GB for dom0 for RPI

[Corey Minyard <minyard@xxxxxxx>]

On Mon, May 18, 2020 at 08:36:08PM +0000, Volodymyr Babchuk wrote:
> Hi Julien,
> 
> On Mon, 2020-05-18 at 12:30 +0100, Julien Grall wrote:
> > From: Julien Grall <jgrall@xxxxxxxxxx>
> > 
> > The raspberry PI 4 has devices that can only DMA into the first GB of
> > the RAM. Therefore we want allocate as much as possible memory below 1GB
> > for dom0.
> > 
> > Use the recently introduced dma_bitsize field to specify the DMA width
> > supported.
> > 
> > Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
> > Reported-by: Corey Minyard <minyard@xxxxxxx>
> > ---
> >  xen/arch/arm/platforms/brcm-raspberry-pi.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/xen/arch/arm/platforms/brcm-raspberry-pi.c 
> > b/xen/arch/arm/platforms/brcm-raspberry-pi.c
> > index b697fa2c6c0e..ad5483437b31 100644
> > --- a/xen/arch/arm/platforms/brcm-raspberry-pi.c
> > +++ b/xen/arch/arm/platforms/brcm-raspberry-pi.c
> > @@ -43,6 +43,7 @@ static const struct dt_device_match rpi4_blacklist_dev[] 
> > __initconst =
> >  PLATFORM_START(rpi4, "Raspberry Pi 4")
> >      .compatible     = rpi4_dt_compat,
> >      .blacklist_dev  = rpi4_blacklist_dev,
> > +    .dma_bitsize    = 10,
> 
> I'm confused. Should it be 30?

Indeed it should.  I just tested this series, and Linux fails to boot
with this set to 10.  With it set to 30 it works.

With this set to 30, you can have a:

Tested-by: Corey Minyard <cminyard@xxxxxxxxxx>

for all three patches.

-corey

> 
> >  PLATFORM_END
> >  
> >  /*