On 9/14/22 14:09, Richard Fitzgerald wrote:
> Only exit sdw_handle_slave_status() right after calling
> sdw_program_device_num() if it actually programmed an ID into at
> least one device.
>
> sdw_handle_slave_status() should protect itself against phantom
> device #0 ATTACHED indications. In that case there is no actual
> device still on #0. The early exit relies on there being a status
> change to ATTACHED on the reprogrammed device to trigger another
> call to sdw_handle_slave_status() which will then handle the status
> of all peripherals. If no device was actually programmed with an
> ID there won't be a new ATTACHED indication. This can lead to the
> status of other peripherals not being handled.
>
> The status passed to sdw_handle_slave_status() is obviously always
> from a point of time in the past, and may indicate accumulated
> unhandled events (depending how the bus manager operates). It's
> possible that a device ID is reprogrammed but the last PING status
> captured state just before that, when it was still reporting on
> ID #0. Then sdw_handle_slave_status() is called with this PING info,
> just before a new PING status is available showing it now on its new
> ID. So sdw_handle_slave_status() will receive a phantom report of a
> device on #0, but it will not find one.
>
> Signed-off-by: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx>
Nice work, thanks Richard
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
> ---
> drivers/soundwire/bus.c | 29 +++++++++++++++++++++--------
> 1 file changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
> index 6e569a875a9b..8eded1a55227 100644
> --- a/drivers/soundwire/bus.c
> +++ b/drivers/soundwire/bus.c
> @@ -729,7 +729,7 @@ void sdw_extract_slave_id(struct sdw_bus *bus,
> }
> EXPORT_SYMBOL(sdw_extract_slave_id);
>
> -static int sdw_program_device_num(struct sdw_bus *bus)
> +static int sdw_program_device_num(struct sdw_bus *bus, bool *programmed)
> {
> u8 buf[SDW_NUM_DEV_ID_REGISTERS] = {0};
> struct sdw_slave *slave, *_s;
> @@ -739,6 +739,8 @@ static int sdw_program_device_num(struct sdw_bus *bus)
> int count = 0, ret;
> u64 addr;
>
> + *programmed = false;
> +
> /* No Slave, so use raw xfer api */
> ret = sdw_fill_msg(&msg, NULL, SDW_SCP_DEVID_0,
> SDW_NUM_DEV_ID_REGISTERS, 0, SDW_MSG_FLAG_READ, buf);
> @@ -797,6 +799,8 @@ static int sdw_program_device_num(struct sdw_bus *bus)
> return ret;
> }
>
> + *programmed = true;
> +
> break;
> }
> }
> @@ -1756,7 +1760,7 @@ int sdw_handle_slave_status(struct sdw_bus *bus,
> {
> enum sdw_slave_status prev_status;
> struct sdw_slave *slave;
> - bool attached_initializing;
> + bool attached_initializing, id_programmed;
> int i, ret = 0;
>
> /* first check if any Slaves fell off the bus */
> @@ -1787,14 +1791,23 @@ int sdw_handle_slave_status(struct sdw_bus *bus,
>
> if (status[0] == SDW_SLAVE_ATTACHED) {
> dev_dbg(bus->dev, "Slave attached, programming device number\n");
> - ret = sdw_program_device_num(bus);
> - if (ret < 0)
> - dev_err(bus->dev, "Slave attach failed: %d\n", ret);
> +
> /*
> - * programming a device number will have side effects,
> - * so we deal with other devices at a later time
> + * Programming a device number will have side effects,
> + * so we deal with other devices at a later time.
> + * This relies on those devices reporting ATTACHED, which will
> + * trigger another call to this function. This will only
> + * happen if at least one device ID was programmed.
> + * Error returns from sdw_program_device_num() are currently
> + * ignored because there's no useful recovery that can be done.
> + * Returning the error here could result in the current status
> + * of other devices not being handled, because if no device IDs
> + * were programmed there's nothing to guarantee a status change
> + * to trigger another call to this function.
> */
> - return ret;
> + sdw_program_device_num(bus, &id_programmed);
> + if (id_programmed)
> + return 0;
> }
>
> /* Continue to check other slave statuses */
