spi: Add SPI_NO_TX/RX support

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>
Link: https://lore.kernel.org/r/20201221152936.53873-2-alexandru.ardelean@analog.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 51d7c00..ca75f40 100644 (file)
--- 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 +3335,16 @@ 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 +3358,8 @@ 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.
         */
@@ -3610,6 +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)
@@ -3623,6 +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/linux/spi/spi.h b/include/linux/spi/spi.h
index a08c3f3..9bfdfaf 100644 (file)
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -6,6 +6,7 @@
 #ifndef __LINUX_SPI_H
 #define __LINUX_SPI_H
 
+#include <linux/bits.h>
 #include <linux/device.h>
 #include <linux/mod_devicetable.h>
 #include <linux/slab.h>
@@ -166,6 +167,18 @@ struct spi_device {
        u8                      chip_select;
        u8                      bits_per_word;
        bool                    rt;
+#define SPI_NO_TX      BIT(31)         /* no transmit wire */
+#define SPI_NO_RX      BIT(30)         /* no receive wire */
+       /*
+        * All bits defined above should be covered by SPI_MODE_KERNEL_MASK.
+        * The SPI_MODE_KERNEL_MASK has the SPI_MODE_USER_MASK counterpart,
+        * which is defined in 'include/uapi/linux/spi/spi.h'.
+        * The bits defined here are from bit 31 downwards, while in
+        * SPI_MODE_USER_MASK are from 0 upwards.
+        * These bits must not overlap. A static assert check should make sure of that.
+        * If adding extra bits, make sure to decrease the bit index below as well.
+        */
+#define SPI_MODE_KERNEL_MASK   (~(BIT(30) - 1))
        u32                     mode;
        int                     irq;
        void                    *controller_state;
@@ -189,6 +202,10 @@ struct spi_device {
         */
 };
 
+/* Make sure that SPI_MODE_KERNEL_MASK & SPI_MODE_USER_MASK don't overlap */
+static_assert((SPI_MODE_KERNEL_MASK & SPI_MODE_USER_MASK) == 0,
+             "SPI_MODE_USER_MASK & SPI_MODE_KERNEL_MASK must not overlap");
+
 static inline struct spi_device *to_spi_device(struct device *dev)
 {
        return dev ? container_of(dev, struct spi_device, dev) : NULL;

diff --git a/include/uapi/linux/spi/spi.h b/include/uapi/linux/spi/spi.h
index 703b586..236a85f 100644 (file)
--- a/include/uapi/linux/spi/spi.h
+++ b/include/uapi/linux/spi/spi.h
@@ -28,4 +28,14 @@
 #define        SPI_RX_OCTAL            _BITUL(14)      /* receive with 8 wires */
 #define        SPI_3WIRE_HIZ           _BITUL(15)      /* high impedance turnaround */
 
+/*
+ * All the bits defined above should be covered by SPI_MODE_USER_MASK.
+ * The SPI_MODE_USER_MASK has the SPI_MODE_KERNEL_MASK counterpart in
+ * 'include/linux/spi/spi.h'. The bits defined here are from bit 0 upwards
+ * while in SPI_MODE_KERNEL_MASK they are from the other end downwards.
+ * These bits must not overlap. A static assert check should make sure of that.
+ * If adding extra bits, make sure to increase the bit index below as well.
+ */
+#define SPI_MODE_USER_MASK     (_BITUL(16) - 1)
+
 #endif /* _UAPI_SPI_H */