On Fri, 2 Feb 2024 at 20:48, Joe Komlodi <koml...@google.com> wrote:
>
> It's possible for a reset to come in the middle of a transaction, which
> causes the bus to be in an old state when a new transaction comes in.
>
> Signed-off-by: Joe Komlodi <koml...@google.com>
> ---
> hw/i2c/core.c | 19 +++++++++++++++++++
> include/hw/i2c/i2c.h | 2 +-
> 2 files changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/hw/i2c/core.c b/hw/i2c/core.c
> index 4cf30b2c86..3128067bba 100644
> --- a/hw/i2c/core.c
> +++ b/hw/i2c/core.c
> @@ -23,10 +23,29 @@ static Property i2c_props[] = {
> DEFINE_PROP_END_OF_LIST(),
> };
>
> +static void i2c_bus_hold_reset(Object *obj)
> +{
> + I2CBus *bus = I2C_BUS(obj);
> + I2CNode *node, *next;
> +
> + bus->broadcast = false;
> + QLIST_FOREACH_SAFE(node, &bus->current_devs, next, next) {
> + QLIST_REMOVE(node, next);
> + g_free(node);
> + }
> +}
This does what it says it's going to do; but I think it
would be good to hear from Corey whether it's better to
do this, or instead to call i2c_end_transfer() in the
reset-enter phase.
Mostly QEMU's "reset" is like power-cycling, in which case
I guess that what we have here where we just forget about
the in-progress transfer and assume the device on the other
end is also going to reset back to a neutral state is what
we want.
Does i2c have a concept of a bus-level "reset" operation?
> +
> +static void i2c_bus_class_init(ObjectClass *klass, void *data)
> +{
> + ResettableClass *rc = RESETTABLE_CLASS(klass);
> + rc->phases.hold = i2c_bus_hold_reset;
> +}
> +
> static const TypeInfo i2c_bus_info = {
> .name = TYPE_I2C_BUS,
> .parent = TYPE_BUS,
> .instance_size = sizeof(I2CBus),
> + .class_init = i2c_bus_class_init,
> };
> static int i2c_bus_pre_save(void *opaque)
> diff --git a/include/hw/i2c/i2c.h b/include/hw/i2c/i2c.h
> index 2a3abacd1b..49580e30e2 100644
> --- a/include/hw/i2c/i2c.h
> +++ b/include/hw/i2c/i2c.h
> @@ -64,7 +64,7 @@ struct I2CSlave {
> };
>
> #define TYPE_I2C_BUS "i2c-bus"
> -OBJECT_DECLARE_SIMPLE_TYPE(I2CBus, I2C_BUS)
> +OBJECT_DECLARE_TYPE(I2CBus, I2CBusClass, I2C_BUS)
I don't think you need this change any more ?
thanks
-- PMM
