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spi: Only call transfer_one() if we have buffers to transfer 

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>
Tested-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Mark Brown <broonie@linaro.org>
hifive-unleashed-5.1
Mark Brown 2014-08-16 16:27:41 +01:00
parent 7d1311b93e
commit 38ec10f60d
1 changed files with 25 additions and 17 deletions
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42
drivers/spi/spi.c
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@ -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);
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;
}
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);