Re: [PATCH v2 06/12] aspeed/smc: Wire CS lines at reset

[Cédric Le Goater]

On 6/7/23 12:49, Joel Stanley wrote:
> On Wed, 7 Jun 2023 at 04:40, Cédric Le Goater <clg@kaod.org> wrote:
> > Currently, a set of default flash devices is created at machine init
> > and drives defined on the QEMU command line are associated to the FMC
> > and SPI controllers in sequence :
> >
> >     -drive file<file>,format=raw,if=mtd
> >     -drive file<file1>,format=raw,if=mtd
> >
> > The CS lines are wired in the same creation loop. This makes a strong
> > assumption on the ordering and is not very flexible since only a
> > limited set of flash devices can be defined : 1 FMC + 1 or 2 SPI,
> > which is less than what the SoC really supports.
> >
> > A better alternative would be to define the flash devices on the
> > command line using a blockdev attached to a CS line of a SSI bus :
> >
> >      -blockdev node-name=fmc0,driver=file,filename=./flash.img
> >      -device mx66u51235f,addr=0x0,bus=ssi.0,drive=fmc0
>
> I don't like the idea of making the command line more complicated
There are benefits to this change and patch 8 :

 - it is possible to define block backends out of order
 - it is possible to define *all* devices backends. Some machines support
   up to 8.
 - it is possible to use different flash models without adding new boards
 - as a consequence, the machine options "spi-model" and "fmc-model" can
   be deprecated. These were a clumsy interface.
 - with -nodefaults, the machine starts running by fetching instructions
   from the FMC0 device, which is what HW does.
 - and the machine option "execute-in-place" can be deprecated.

> That is not a comment on this patch though, but it would be nice if we
> could head towards decreasing the complexity.

Describing the devices on various buses comes at a cost.

Using -drive is still possible. It should be considered an optimization
loading the FMC0 contents as a ROM to speedup boot.

Thanks,

C.


> > However, user created flash devices are not correctly wired to their
> > SPI controller and consequently can not be used by the machine. Fix
> > that and wire the CS lines of all available devices when the SSI bus
> > is reset.
> >
> > Signed-off-by: Cédric Le Goater <clg@kaod.org>
>
> Reviewed-by: Joel Stanley <joel@jms.id.au>
>
>
> > ---
> >   hw/arm/aspeed.c     | 5 +----
> >   hw/ssi/aspeed_smc.c | 8 ++++++++
> >   2 files changed, 9 insertions(+), 4 deletions(-)
> >
> > diff --git a/hw/arm/aspeed.c b/hw/arm/aspeed.c
> > index 76a1e7303de1..e5a49bb0b1a7 100644
> > --- a/hw/arm/aspeed.c
> > +++ b/hw/arm/aspeed.c
> > @@ -299,17 +299,14 @@ void aspeed_board_init_flashes(AspeedSMCState *s, const 
> > char *flashtype,
> >
> >       for (i = 0; i < count; ++i) {
> >           DriveInfo *dinfo = drive_get(IF_MTD, 0, unit0 + i);
> > -        qemu_irq cs_line;
> >           DeviceState *dev;
> >
> >           dev = qdev_new(flashtype);
> >           if (dinfo) {
> >               qdev_prop_set_drive(dev, "drive", blk_by_legacy_dinfo(dinfo));
> >           }
> > +        qdev_prop_set_uint8(dev, "addr", i);
> >           qdev_realize_and_unref(dev, BUS(s->spi), &error_fatal);
> > -
> > -        cs_line = qdev_get_gpio_in_named(dev, SSI_GPIO_CS, 0);
> > -        qdev_connect_gpio_out_named(DEVICE(s), "cs", i, cs_line);
> >       }
> >   }
> >
> > diff --git a/hw/ssi/aspeed_smc.c b/hw/ssi/aspeed_smc.c
> > index 72811693224d..2a4001b774a2 100644
> > --- a/hw/ssi/aspeed_smc.c
> > +++ b/hw/ssi/aspeed_smc.c
> > @@ -692,6 +692,14 @@ static void aspeed_smc_reset(DeviceState *d)
> >           memset(s->regs, 0, sizeof s->regs);
> >       }
> >
> > +    for (i = 0; i < asc->cs_num_max; i++) {
> > +        DeviceState *dev = ssi_get_cs(s->spi, i);
> > +        if (dev) {
> > +            qemu_irq cs_line = qdev_get_gpio_in_named(dev, SSI_GPIO_CS, 0);
> > +            qdev_connect_gpio_out_named(DEVICE(s), "cs", i, cs_line);
> > +        }
> > +    }
> > +
> >       /* Unselect all peripherals */
> >       for (i = 0; i < asc->cs_num_max; ++i) {
> >           s->regs[s->r_ctrl0 + i] |= CTRL_CE_STOP_ACTIVE;
> > --
> > 2.40.1