From: Mark Brown broonie@linaro.org

Client drivers such as the ChomeOS EC driver sometimes use transfers with no buffers and only a delay specified in order to allow a delay after the assertion of /CS. Rather than require controller drivers handle this noop case gracefully put checks in the core to ensure that we don't call into the controller for such transfers.

Reported-by: Addy Ke addy.ke@rock-chips.com Signed-off-by: Mark Brown broonie@linaro.org ---

Completely untested at this point.

drivers/spi/spi.c | 44 ++++++++++++++++++++++++++------------------ 1 file changed, 26 insertions(+), 18 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index ca935df..95cfe3b 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -789,27 +789,35 @@ static int spi_transfer_one_message(struct spi_master *master, list_for_each_entry(xfer, &msg->transfers, transfer_list) { trace_spi_transfer_start(msg, xfer);

- reinit_completion(&master->xfer_completion); - - ret = master->transfer_one(master, msg->spi, xfer); - if (ret < 0) { - dev_err(&msg->spi->dev, - "SPI transfer failed: %d\n", ret); - goto out; - } + if (xfer->tx_buf || xfer->rx_buf) { + reinit_completion(&master->xfer_completion); + + ret = master->transfer_one(master, msg->spi, xfer); + if (ret < 0) { + dev_err(&msg->spi->dev, + "SPI transfer failed: %d\n", ret); + goto out; + }

- if (ret > 0) { - ret = 0; - ms = xfer->len * 8 * 1000 / xfer->speed_hz; - ms += ms + 100; /* some tolerance */ + if (ret > 0) { + ret = 0; + ms = xfer->len * 8 * 1000 / xfer->speed_hz; + ms += ms + 100; /* some tolerance */

- ms = wait_for_completion_timeout(&master->xfer_completion, - msecs_to_jiffies(ms)); - } + ms = wait_for_completion_timeout(&master->xfer_completion, + msecs_to_jiffies(ms)); + }

- if (ms == 0) { - dev_err(&msg->spi->dev, "SPI transfer timed out\n"); - msg->status = -ETIMEDOUT; + if (ms == 0) { + dev_err(&msg->spi->dev, + "SPI transfer timed out\n"); + msg->status = -ETIMEDOUT; + } + } else { + if (xfer->len) + dev_err(&msg->spi->dev, + "Bufferless transfer has length %u\n", + xfer->len); }

trace_spi_transfer_stop(msg, xfer);