From: Alexandru Ardelean <alexandru.ardelean@analog.com>
To: <linux-spi@vger.kernel.org>, <devicetree@vger.kernel.org>,
<linux-kernel@vger.kernel.org>
Cc: <robh+dt@kernel.org>, <broonie@kernel.org>,
<andy.shevchenko@gmail.com>, <dragos.bogdan@analog.com>,
Alexandru Ardelean <alexandru.ardelean@analog.com>
Subject: [PATCH v3 2/3] spi: Add SPI_NO_TX/RX support
Date: Fri, 27 Nov 2020 15:08:33 +0200 [thread overview]
Message-ID: <20201127130834.136348-2-alexandru.ardelean@analog.com> (raw)
In-Reply-To: <20201127130834.136348-1-alexandru.ardelean@analog.com>
From: Dragos Bogdan <dragos.bogdan@analog.com>
Transmit/receive only is a valid SPI mode. For example, the MOSI/TX line
might be missing from an ADC while for a DAC the MISO/RX line may be
optional. This patch adds these two new modes: SPI_NO_TX and
SPI_NO_RX. This way, the drivers will be able to identify if any of
these two lines is missing and to adjust the transfers accordingly.
Signed-off-by: Dragos Bogdan <dragos.bogdan@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
drivers/spi/spi.c | 26 +++++++++++++++++++++-----
include/uapi/linux/spi/spi.h | 2 ++
2 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index cd3c395b4e90..17d4004bd2c6 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1941,6 +1941,9 @@ static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
/* Device DUAL/QUAD mode */
if (!of_property_read_u32(nc, "spi-tx-bus-width", &value)) {
switch (value) {
+ case 0:
+ spi->mode |= SPI_NO_TX;
+ break;
case 1:
break;
case 2:
@@ -1962,6 +1965,9 @@ static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
if (!of_property_read_u32(nc, "spi-rx-bus-width", &value)) {
switch (value) {
+ case 0:
+ spi->mode |= SPI_NO_RX;
+ break;
case 1:
break;
case 2:
@@ -3329,12 +3335,17 @@ int spi_setup(struct spi_device *spi)
unsigned bad_bits, ugly_bits;
int status;
- /* check mode to prevent that DUAL and QUAD set at the same time
+ /*
+ * check mode to prevent that any two of DUAL, QUAD and NO_MOSI/MISO
+ * are set at the same time
*/
- if (((spi->mode & SPI_TX_DUAL) && (spi->mode & SPI_TX_QUAD)) ||
- ((spi->mode & SPI_RX_DUAL) && (spi->mode & SPI_RX_QUAD))) {
+ if ((hweight_long(spi->mode &
+ (SPI_TX_DUAL | SPI_TX_QUAD | SPI_NO_TX)) > 1) ||
+ (hweight_long(spi->mode &
+ (SPI_RX_DUAL | SPI_RX_QUAD | SPI_NO_RX)) > 1)) {
dev_err(&spi->dev,
- "setup: can not select dual and quad at the same time\n");
+ "setup: can not select any two of dual, quad and no-rx/tx "
+ "at the same time\n");
return -EINVAL;
}
/* if it is SPI_3WIRE mode, DUAL and QUAD should be forbidden
@@ -3348,7 +3359,8 @@ int spi_setup(struct spi_device *spi)
* SPI_CS_WORD has a fallback software implementation,
* so it is ignored here.
*/
- bad_bits = spi->mode & ~(spi->controller->mode_bits | SPI_CS_WORD);
+ bad_bits = spi->mode & ~(spi->controller->mode_bits | SPI_CS_WORD |
+ SPI_NO_TX | SPI_NO_RX);
/* nothing prevents from working with active-high CS in case if it
* is driven by GPIO.
*/
@@ -3609,6 +3621,8 @@ static int __spi_validate(struct spi_device *spi, struct spi_message *message)
* 2. check tx/rx_nbits match the mode in spi_device
*/
if (xfer->tx_buf) {
+ if (spi->mode & SPI_NO_TX)
+ return -EINVAL;
if (xfer->tx_nbits != SPI_NBITS_SINGLE &&
xfer->tx_nbits != SPI_NBITS_DUAL &&
xfer->tx_nbits != SPI_NBITS_QUAD)
@@ -3622,6 +3636,8 @@ static int __spi_validate(struct spi_device *spi, struct spi_message *message)
}
/* check transfer rx_nbits */
if (xfer->rx_buf) {
+ if (spi->mode & SPI_NO_RX)
+ return -EINVAL;
if (xfer->rx_nbits != SPI_NBITS_SINGLE &&
xfer->rx_nbits != SPI_NBITS_DUAL &&
xfer->rx_nbits != SPI_NBITS_QUAD)
diff --git a/include/uapi/linux/spi/spi.h b/include/uapi/linux/spi/spi.h
index ae028d64c779..b504e46a6f18 100644
--- a/include/uapi/linux/spi/spi.h
+++ b/include/uapi/linux/spi/spi.h
@@ -43,5 +43,7 @@
#define SPI_TX_OCTAL 0x2000 /* transmit with 8 wires */
#define SPI_RX_OCTAL 0x4000 /* receive with 8 wires */
#define SPI_3WIRE_HIZ 0x8000 /* high impedance turnaround */
+#define SPI_NO_TX 0x10000 /* no transmit wire */
+#define SPI_NO_RX 0x20000 /* no receive wire */
#endif /* _UAPI_SPI_H */
--
2.27.0
next prev parent reply other threads:[~2020-11-27 13:08 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-27 13:08 [PATCH v3 1/3] spi: uapi: unify SPI modes into a single spi.h header Alexandru Ardelean
2020-11-27 13:08 ` Alexandru Ardelean [this message]
2020-11-27 14:22 ` [PATCH v3 2/3] spi: Add SPI_NO_TX/RX support Andy Shevchenko
2020-11-27 14:23 ` Andy Shevchenko
2020-12-03 8:20 ` Ardelean, Alexandru
2020-12-03 9:47 ` Mark Brown
2020-11-27 13:08 ` [PATCH v3 3/3] spi: dt-bindings: document zero value for spi-{rx,tx}-bus-width properties Alexandru Ardelean
2020-11-27 14:26 ` Andy Shevchenko
2020-12-03 13:35 ` Ardelean, Alexandru
2020-11-27 14:12 ` [PATCH v3 1/3] spi: uapi: unify SPI modes into a single spi.h header Andy Shevchenko
2020-12-03 8:15 ` Ardelean, Alexandru
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