On Tue, Dec 03, 2024 at 10:23:18AM +0000, Łukasz Bartosik wrote:
> OPM PPM LPM
> | 1.send cmd | |
> |-------------------------->| |
> | |-- |
> | | | 2.set busy bit in CCI |
> | |<- |
> | 3.notify the OPM | |
> |<--------------------------| |
> | | 4.send cmd to be executed |
> | |-------------------------->|
> | | |
> | | 5.cmd completed |
> | |<--------------------------|
> | | |
> | |-- |
> | | | 6.set cmd completed |
> | |<- bit in CCI |
> | | |
> | 7.notify the OPM | |
> |<--------------------------| |
> | | |
> | 8.handle notification | |
> | from point 3, read CCI | |
> |<--------------------------| |
> | | |
>
> When the PPM receives command from the OPM (p.1) it sets the busy bit
> in the CCI (p.2), sends notification to the OPM (p.3) and forwards the
> command to be executed by the LPM (p.4). When the PPM receives command
> completion from the LPM (p.5) it sets command completion bit in the CCI
> (p.6) and sends notification to the OPM (p.7). If command execution by
> the LPM is fast enough then when the OPM starts handling the notification
> from p.3 in p.8 and reads the CCI value it will see command completion bit
> set and will call complete(). Then complete() might be called again when
> the OPM handles notification from p.7.
>
> This fix replaces test_bit() with test_and_clear_bit()
> in ucsi_notify_common() in order to call complete() only
> once per request.
>
> This fix also reinitializes completion variable in
> ucsi_sync_control_common() before a command is sent.
>
> Fixes: 584e8df58942 ("usb: typec: ucsi: extract common code for command handling")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Łukasz Bartosik <ukaszb@xxxxxxxxxxxx>
Reviewed-by: Benson Leung <bleung@xxxxxxxxxxxx>
> ---
>
> Changes in v2:
> - Swapped points 7 and 8 in the commit description
> in order to make diagram more clear.
> - Added reinitialization of completion variable
> in the ucsi_sync_control_common().
> ---
>
> drivers/usb/typec/ucsi/ucsi.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> index c435c0835744..7a65a7672e18 100644
> --- a/drivers/usb/typec/ucsi/ucsi.c
> +++ b/drivers/usb/typec/ucsi/ucsi.c
> @@ -46,11 +46,11 @@ void ucsi_notify_common(struct ucsi *ucsi, u32 cci)
> ucsi_connector_change(ucsi, UCSI_CCI_CONNECTOR(cci));
>
> if (cci & UCSI_CCI_ACK_COMPLETE &&
> - test_bit(ACK_PENDING, &ucsi->flags))
> + test_and_clear_bit(ACK_PENDING, &ucsi->flags))
> complete(&ucsi->complete);
>
> if (cci & UCSI_CCI_COMMAND_COMPLETE &&
> - test_bit(COMMAND_PENDING, &ucsi->flags))
> + test_and_clear_bit(COMMAND_PENDING, &ucsi->flags))
> complete(&ucsi->complete);
> }
> EXPORT_SYMBOL_GPL(ucsi_notify_common);
> @@ -65,6 +65,8 @@ int ucsi_sync_control_common(struct ucsi *ucsi, u64 command)
> else
> set_bit(COMMAND_PENDING, &ucsi->flags);
>
> + reinit_completion(&ucsi->complete);
> +
> ret = ucsi->ops->async_control(ucsi, command);
> if (ret)
> goto out_clear_bit;
> --
> 2.47.0.338.g60cca15819-goog
>
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