npcx: driver: SPI: extend driver to support concurrent mode

This CL extends the SPI controller driver to support the concurrent
transaction:
- if the parameter "rxlen" is set to SPI_READBACK_ALL when
spi_transaction() is called, the received data during the transmission
phase should be stored in the "rxdata" buffer.

BRANCH=none
BUG=b:268286582
TEST=Loopback test on the npcx9 EVB, make sure the received data in the
rxdata buffer is the same as that in the txdata buffer.

Change-Id: Ia5ae17fefb69ce18709ded87693b34ed861f4997
Signed-off-by: Jun Lin <CHLin56@nuvoton.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/4259466
Tested-by: CH Lin <chlin56@nuvoton.com>
Reviewed-by: CH Lin <chlin56@nuvoton.com>
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-by: David Cross <davidmcross@google.com>
Commit-Queue: David Cross <davidmcross@google.com>
Reviewed-by: Bobby Casey <bobbycasey@google.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/chip/npcx/spi.c b/chip/npcx/spi.c
index bbe6b33a9d..f152869bc5 100644
--- a/chip/npcx/spi.c
+++ b/chip/npcx/spi.c
@@ -148,9 +148,19 @@ int spi_transaction(const struct spi_device_t *spi_device,
 		/* Waiting till reading is finished */
 		while (!IS_BIT_SET(NPCX_SPI_STAT, NPCX_SPI_STAT_RBF))
 			;
-		/* Reading the (unused) data */
-		clear_databuf();
+
+		if (rxlen == SPI_READBACK_ALL) {
+			rxdata[i] = (uint8_t)NPCX_SPI_DATA;
+			CPRINTS("rxdata[i]=%x", rxdata[i]);
+		} else {
+			/* Reading the (unused) data to empty the read buffer */
+			clear_databuf();
+		}
 	}
+
+	if (rxlen == SPI_READBACK_ALL)
+		goto terminate;
+
 	CPRINTS("write end");
 	/* Reading the data */
 	for (i = 0; i < rxlen; ++i) {
@@ -166,6 +176,8 @@ int spi_transaction(const struct spi_device_t *spi_device,
 		rxdata[i] = (uint8_t)NPCX_SPI_DATA;
 		CPRINTS("rxdata[i]=%x", rxdata[i]);
 	}
+
+terminate:
 	/* Deassert CS# (high) to end transaction */
 	gpio_set_level(gpio, 1);
 	mutex_unlock(&spi_lock);