On 06/28/2016 09:30 PM, miny...@acm.org wrote:
> From: Corey Minyard <cminy...@mvista.com>
>
> Change 2293c27faddf (i2c: implement broadcast write) added broadcast
> capability to the I2C bus, but it broke SMBus read transactions.
> An SMBus read transaction does two i2c_start_transaction() calls
> without an intervening i2c_end_transfer() call. This will
> result in i2c_start_transfer() adding the same device to the
> current_devs list twice, and then the ->event() for the same
> device gets called twice in the second call to i2c_start_transfer(),
> resulting in the smbus code getting confused.
Hi Corey,
I didn't know that we can do two i2c_start_transfer without an
end_transfert in the middle. Maybe worth a comment in the code?
Otherwise:
Reviewed-by: KONRAD Frederic <fred.kon...@greensocs.com>
Tested-by: KONRAD Frederic <fred.kon...@greensocs.com>
Thanks,
Fred
>
> Note that this happens even with pure I2C devices when simulating
> SMBus over I2C.
>
> This fix only scans the bus if the current set of devices is empty.
> This means that the current set of devices stays fixed until
> i2c_end_transfer() is called, which is really what you want.
>
> This also deletes the empty check from the top of i2c_end_transfer().
> It's unnecessary, and it prevents the broadcast variable from being
> set to false at the end of the transaction if no devices were on
> the bus.
>
> Cc: KONRAD Frederic <fred.kon...@greensocs.com>
> Cc: Alistair Francis <alistair.fran...@xilinx.com>
> Cc: Peter Crosthwaite <crosthwaite.pe...@gmail.com>
> Cc: Kwon <hyun.k...@xilinx.com>
> Cc: Peter Maydell <peter.mayd...@linaro.org>
> Signed-off-by: Corey Minyard <cminy...@mvista.com>
> ---
> hw/i2c/core.c | 28 +++++++++++++++-------------
> 1 file changed, 15 insertions(+), 13 deletions(-)
>
> This fix should work with I2C devices as well as SMBus devices.
>
> Sorry for not thinking it through all the way before.
>
> diff --git a/hw/i2c/core.c b/hw/i2c/core.c
> index abb3efb..6313d31 100644
> --- a/hw/i2c/core.c
> +++ b/hw/i2c/core.c
> @@ -101,15 +101,21 @@ int i2c_start_transfer(I2CBus *bus, uint8_t address,
> int recv)
> bus->broadcast = true;
> }
>
> - QTAILQ_FOREACH(kid, &bus->qbus.children, sibling) {
> - DeviceState *qdev = kid->child;
> - I2CSlave *candidate = I2C_SLAVE(qdev);
> - if ((candidate->address == address) || (bus->broadcast)) {
> - node = g_malloc(sizeof(struct I2CNode));
> - node->elt = candidate;
> - QLIST_INSERT_HEAD(&bus->current_devs, node, next);
> - if (!bus->broadcast) {
> - break;
> + /*
> + * If there are already devices in the list, that means we are in
> + * the middle of a transaction and we shouldn't rescan the bus.
> + */
> + if (QLIST_EMPTY(&bus->current_devs)) {
> + QTAILQ_FOREACH(kid, &bus->qbus.children, sibling) {
> + DeviceState *qdev = kid->child;
> + I2CSlave *candidate = I2C_SLAVE(qdev);
> + if ((candidate->address == address) || (bus->broadcast)) {
> + node = g_malloc(sizeof(struct I2CNode));
> + node->elt = candidate;
> + QLIST_INSERT_HEAD(&bus->current_devs, node, next);
> + if (!bus->broadcast) {
> + break;
> + }
> }
> }
> }
> @@ -134,10 +140,6 @@ void i2c_end_transfer(I2CBus *bus)
> I2CSlaveClass *sc;
> I2CNode *node, *next;
>
> - if (QLIST_EMPTY(&bus->current_devs)) {
> - return;
> - }
> -
> QLIST_FOREACH_SAFE(node, &bus->current_devs, next, next) {
> sc = I2C_SLAVE_GET_CLASS(node->elt);
> if (sc->event) {
>
