Add support for registering SPI slave controllers using the existing SPI
master framework:
- SPI slave controllers must set the SPI_MASTER_IS_SLAVE flag in
spi_master.flags,
- The "cs-gpios" property is ignored,
- The bus is described in DT as having a single slave node, "reg" and
"spi-max-frequency" properties are ignored.
>From the point of view of an SPI slave protocol handler, an SPI slave
controller looks exactly like an ordinary SPI master controller.
Signed-off-by: Geert Uytterhoeven <[email protected]>
---
Should we rename spi_master to spi_controller?
---
drivers/spi/Kconfig | 14 +++++++++++++-
drivers/spi/Makefile | 2 ++
drivers/spi/spi.c | 39 ++++++++++++++++++++++++---------------
include/linux/spi/spi.h | 5 +++--
4 files changed, 42 insertions(+), 18 deletions(-)
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 4b931ec8d90b610f..00e990d91a715c0e 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -736,6 +736,18 @@ config SPI_TLE62X0
endif # SPI_MASTER
-# (slave support would go here)
+#
+# SLAVE side ... listening to other SPI masters
+#
+
+config SPI_SLAVE
+ bool "SPI slave protocol handlers"
+ help
+ If your system has a slave-capable SPI controller, you can enable
+ slave protocol handlers.
+
+if SPI_SLAVE
+
+endif # SPI_SLAVE
endif # SPI
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 3c74d003535bb9fb..71d02939080fb747 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -97,3 +97,5 @@ obj-$(CONFIG_SPI_XILINX) += spi-xilinx.o
obj-$(CONFIG_SPI_XLP) += spi-xlp.o
obj-$(CONFIG_SPI_XTENSA_XTFPGA) += spi-xtensa-xtfpga.o
obj-$(CONFIG_SPI_ZYNQMP_GQSPI) += spi-zynqmp-gqspi.o
+
+# SPI slave protocol handlers
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 77e6e45951f4c5e1..6ea32255d6d9e780 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1462,6 +1462,7 @@ err_init_queue:
static struct spi_device *
of_register_spi_device(struct spi_master *master, struct device_node *nc)
{
+ bool slave = master->flags & SPI_MASTER_IS_SLAVE;
struct spi_device *spi;
int rc;
u32 value;
@@ -1485,13 +1486,16 @@ of_register_spi_device(struct spi_master *master,
struct device_node *nc)
}
/* Device address */
- rc = of_property_read_u32(nc, "reg", &value);
- if (rc) {
- dev_err(&master->dev, "%s has no valid 'reg' property (%d)\n",
- nc->full_name, rc);
- goto err_out;
+ if (!slave) {
+ rc = of_property_read_u32(nc, "reg", &value);
+ if (rc) {
+ dev_err(&master->dev,
+ "%s has no valid 'reg' property (%d)\n",
+ nc->full_name, rc);
+ goto err_out;
+ }
+ spi->chip_select = value;
}
- spi->chip_select = value;
/* Mode (clock phase/polarity/etc.) */
if (of_find_property(nc, "spi-cpha", NULL))
@@ -1543,13 +1547,16 @@ of_register_spi_device(struct spi_master *master,
struct device_node *nc)
}
/* Device speed */
- rc = of_property_read_u32(nc, "spi-max-frequency", &value);
- if (rc) {
- dev_err(&master->dev, "%s has no valid 'spi-max-frequency'
property (%d)\n",
- nc->full_name, rc);
- goto err_out;
+ if (!slave) {
+ rc = of_property_read_u32(nc, "spi-max-frequency", &value);
+ if (rc) {
+ dev_err(&master->dev,
+ "%s has no valid 'spi-max-frequency' property
(%d)\n",
+ nc->full_name, rc);
+ goto err_out;
+ }
+ spi->max_speed_hz = value;
}
- spi->max_speed_hz = value;
/* Store a pointer to the node in the device structure */
of_node_get(nc);
@@ -1779,7 +1786,7 @@ static int of_spi_register_master(struct spi_master
*master)
int nb, i, *cs;
struct device_node *np = master->dev.of_node;
- if (!np)
+ if (!np || master->flags & SPI_MASTER_IS_SLAVE)
return 0;
nb = of_gpio_named_count(np, "cs-gpios");
@@ -1885,8 +1892,10 @@ int spi_register_master(struct spi_master *master)
status = device_add(&master->dev);
if (status < 0)
goto done;
- dev_dbg(dev, "registered master %s%s\n", dev_name(&master->dev),
- dynamic ? " (dynamic)" : "");
+ dev_dbg(dev, "registered %s %s%s\n",
+ master->flags & SPI_MASTER_IS_SLAVE ? "slave"
+ : "master",
+ dev_name(&master->dev), dynamic ? " (dynamic)" : "");
/* If we're using a queued driver, start the queue */
if (master->transfer)
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 1f03483f61e5714b..0fbebaa7d93990a4 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -28,8 +28,8 @@ struct spi_transfer;
struct spi_flash_read_message;
/*
- * INTERFACES between SPI master-side drivers and SPI infrastructure.
- * (There's no SPI slave support for Linux yet...)
+ * INTERFACES between SPI master-side drivers and SPI slave protocol handers,
+ * and SPI infrastructure.
*/
extern struct bus_type spi_bus_type;
@@ -439,6 +439,7 @@ struct spi_master {
#define SPI_MASTER_NO_TX BIT(2) /* can't do buffer write */
#define SPI_MASTER_MUST_RX BIT(3) /* requires rx */
#define SPI_MASTER_MUST_TX BIT(4) /* requires tx */
+#define SPI_MASTER_IS_SLAVE BIT(5) /* SPI slave controller */
/*
* on some hardware transfer size may be constrained
--
1.9.1
