[PATCH] qemu: arm: Scan the pci bus in board_init

[Simon Glass]

Hi Heinrich,

On Tue, 31 Dec 2019 at 09:59, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> On 12/31/19 4:49 PM, Sughosh Ganu wrote:
> >
> > On Tue, 31 Dec 2019 at 20:38, Heinrich Schuchardt <xypron.glpk at gmx.de
> > <mailto:xypron.glpk at gmx.de>> wrote:
> >
> >     On 12/31/19 2:31 PM, Sughosh Ganu wrote:
> >      > Scan the pci bus in board_init routine before scanning the virtio
> >      > devices. This enumerates all the virtio devices, including devices
> >      > found on the pci bus.
> >      >
> >      > Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org
> >     <mailto:sughosh.ganu at linaro.org>>
> >      > ---
> >      >  board/emulation/qemu-arm/qemu-arm.c | 7 +++++++
> >      >  1 file changed, 7 insertions(+)
> >      >
> >      > diff --git a/board/emulation/qemu-arm/qemu-arm.c
> >     b/board/emulation/qemu-arm/qemu-arm.c
> >      > index 4e18733..6c5335c 100644
> >      > --- a/board/emulation/qemu-arm/qemu-arm.c
> >      > +++ b/board/emulation/qemu-arm/qemu-arm.c
> >      > @@ -63,6 +63,13 @@ struct mm_region *mem_map = qemu_arm64_mem_map;
> >      >  int board_init(void)
> >      >  {
> >      >       /*
> >      > +      * Scan the pci bus before calling virtio_init. This
> >      > +      * enumerates all virtio devices, including devices
> >      > +      * on the pci bus.
> >
> >     The last sentence is easy to misunderstand. You surely do not mean that
> >     pci_init() would enumerate all virtio devices including mmio virtio
> >     devices.
> >
> >     I would suggest to rephrase it to "This enumerates all pci devices
> >     including virtio devices on the pci bus."
> >
> >
> > Ok.
> >
> >
> >     With the patch I no longer need to run `virtio scan` on
> >     qemu_arm64_defonfig before using the rng command supplied in patch
> >
> >     [PATCH 1/1] cmd: add rng command
> >     https://lists.denx.de/pipermail/u-boot/2019-December/394539.html
> >
> >     Unfortunately you only considered the ARM architecture. We need a
> >     solution that works on all QEMU architectures (MIPS, RISC-V, X86, ARM).
> >
> >
> > That is fine with me, but currently, only risc-v and arm architectures
> > are calling virtio_init.
> >
> >
> >     How about eliminating board_init() for ARM and RISC-V and moving
> >     virtio_init() to common/board_r.c after initr_pci?
> >
> >
> > That can be done, but currently, for some reason, initr_pci function
> > calls pci_init only when CONFIG_DM_PCI is not defined. Not sure why that
> > is the case, although initr_pci gets called after initr_dm.
> >
> > -sughosh
>
> This dates back to Simon's commit ff3e077bd23c ("dm: pci: Add a uclass
> for PCI").
>
> I hope that Simon can tell us why he chose not to call pci_init() if
> DM_PCI is defined.

Driver model uses lazy init. We have discussed this before, and
considered using a uclass flag to tell U-Boot that the uclass needs to
be fully probed (i.e. probe all devices in that uclass, recursively).

But I'm not sure we got agreement. If you think it is a good idea you
could send a patch. The only thing is that I think some platforms
don't need PCI to boot so might not want this?

Regards,
Simon