On Mon, 2025-03-24 at 12:35 +0000, Tudor Ambarus wrote:
> When we're polling for responses and get a response that corresponds to
> another request, we save the RX data in order to drain the RX queue.
>
> If the response for the current request is not found in the request's
> iteration of the queue, or if the queue is empty, we must check whether
> the RX data was saved by a previous request when it drained the RX queue.
>
> We failed to check for already saved responses when the queue was empty,
> and requests could time out. Check saved RX before bailing out on empty
> RX queue.
>
> Fixes: a88927b534ba ("firmware: add Exynos ACPM protocol driver")
> Reported-by: André Draszik <andre.draszik@xxxxxxxxxx>
> Signed-off-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxx>
> ---
> on top of krzk/for-next
> ---
> drivers/firmware/samsung/exynos-acpm.c | 44 +++++++++++++++++++++++-----------
> 1 file changed, 30 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/firmware/samsung/exynos-acpm.c b/drivers/firmware/samsung/exynos-acpm.c
> index a85b2dbdd9f0d7b1f327f54a0a283e4f32587a98..15e991b99f5a384a299c1baf6b279fc93244bcf2 100644
> --- a/drivers/firmware/samsung/exynos-acpm.c
> +++ b/drivers/firmware/samsung/exynos-acpm.c
> @@ -184,6 +184,29 @@ struct acpm_match_data {
> #define client_to_acpm_chan(c) container_of(c, struct acpm_chan, cl)
> #define handle_to_acpm_info(h) container_of(h, struct acpm_info, handle)
>
> +/**
> + * acpm_get_saved_rx() - get the response if it was already saved.
> + * @achan: ACPM channel info.
> + * @xfer: reference to the transfer to get response for.
> + * @tx_seqnum: xfer TX sequence number.
> + */
> +static void acpm_get_saved_rx(struct acpm_chan *achan,
> + const struct acpm_xfer *xfer, u32 tx_seqnum)
> +{
> + const struct acpm_rx_data *rx_data = &achan->rx_data[tx_seqnum - 1];
> + u32 rx_seqnum;
> +
> + if (!rx_data->response)
> + return;
> +
> + rx_seqnum = FIELD_GET(ACPM_PROTOCOL_SEQNUM, rx_data->cmd[0]);
> +
> + if (rx_seqnum == tx_seqnum) {
To help the casual reader, maybe add a comment to say that this condition is true
if/when the response was received, and before reception rx_seqnum will be == 0,
because acpm_prepare_xfer() clears it - i.e. it is not ever supposed to be any
arbitrary number. It's kinda implied, but a comment like that would make this
more explicit. If I'm getting this all right.
Other that that;
Reviewed-by: André Draszik <andre.draszik@xxxxxxxxxx>
Tested-by: André Draszik <andre.draszik@xxxxxxxxxx>
> + memcpy(xfer->rxd, rx_data->cmd, xfer->rxlen);
> + clear_bit(rx_seqnum - 1, achan->bitmap_seqnum);
> + }
> +}
> +
> /**
> * acpm_get_rx() - get response from RX queue.
> * @achan: ACPM channel info.
> @@ -204,15 +227,16 @@ static int acpm_get_rx(struct acpm_chan *achan, const struct acpm_xfer *xfer)
> rx_front = readl(achan->rx.front);
> i = readl(achan->rx.rear);
>
> - /* Bail out if RX is empty. */
> - if (i == rx_front)
> + tx_seqnum = FIELD_GET(ACPM_PROTOCOL_SEQNUM, xfer->txd[0]);
> +
> + if (i == rx_front) {
> + acpm_get_saved_rx(achan, xfer, tx_seqnum);
> return 0;
> + }
>
> base = achan->rx.base;
> mlen = achan->mlen;
>
> - tx_seqnum = FIELD_GET(ACPM_PROTOCOL_SEQNUM, xfer->txd[0]);
> -
> /* Drain RX queue. */
> do {
> /* Read RX seqnum. */
> @@ -259,16 +283,8 @@ static int acpm_get_rx(struct acpm_chan *achan, const struct acpm_xfer *xfer)
> * If the response was not in this iteration of the queue, check if the
> * RX data was previously saved.
> */
> - rx_data = &achan->rx_data[tx_seqnum - 1];
> - if (!rx_set && rx_data->response) {
> - rx_seqnum = FIELD_GET(ACPM_PROTOCOL_SEQNUM,
> - rx_data->cmd[0]);
> -
> - if (rx_seqnum == tx_seqnum) {
> - memcpy(xfer->rxd, rx_data->cmd, xfer->rxlen);
> - clear_bit(rx_seqnum - 1, achan->bitmap_seqnum);
> - }
> - }
> + if (!rx_set)
> + acpm_get_saved_rx(achan, xfer, tx_seqnum);
>
> return 0;
> }
>
> ---
> base-commit: f0dbe0d40d08199109cb689849877694a8b91033
> change-id: 20250324-acpm-drained-rx-queue-ec316d4cbcdf
>
> Best regards,
