[PATCH v1 03/14] serial: port: Introduce a common helper to read properties

Andy Shevchenko
2024-02-21T18:34:58Z

Several serial drivers want to read the same or similar set of
the port properties. Make a common helper for them.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
drivers/tty/serial/serial_port.c | 135 +++++++++++++++++++++++++++++++
include/linux/serial_core.h | 1 +
2 files changed, 136 insertions(+)

diff --git a/drivers/tty/serial/serial_port.c b/drivers/tty/serial/serial_port.c
index 88975a4df306..111e1f25fbc6 100644
--- a/drivers/tty/serial/serial_port.c
+++ b/drivers/tty/serial/serial_port.c
@@ -8,7 +8,10 @@

#include <linux/device.h>
#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
+#include <linux/property.h>
#include <linux/serial_core.h>
#include <linux/spinlock.h>

@@ -82,6 +85,138 @@ void uart_remove_one_port(struct uart_driver *drv, struct uart_port *port)
}
EXPORT_SYMBOL(uart_remove_one_port);

+/**
+ * uart_read_port_properties - read firmware properties of the given UART port
+ * @port: corresponding port
+ * @use_defaults: apply defaults or validate the values
+ *
+ * The following device properties are supported:
+ * - clock-frequency (optional)
+ * - fifo-size (optional)
+ * - no-loopback-test (optional)
+ * - reg-shift (defaults may apply)
+ * - reg-offset (value may be validated)
+ * - reg-io-width (defaults may apply or value may be validated)
+ * - interrupts (OF only)
+ * - serial [alias ID] (OF only)
+ *
+ * If the port->dev is of struct platform_device type the interrupt line
+ * will be retrieved via platform_get_irq() call against that device.
+ * Otherwise it will be assigned by fwnode_irq_get() call. In both cases
+ * the index 0 of the resource is used.
+ *
+ * The caller is responsible to initialize the following fields of the @port
+ * ->dev (must be valid)
+ * ->flags
+ * ->iotype (if @use_defaults is false)
+ * ->mapbase
+ * ->mapsize
+ * ->regshift (if @use_defaults is false)
+ * before calling this function. Alternatively the above mentioned fields
+ * may be zeroed, in such case the only ones, that have associated properties
+ * found, will be set to the respective values.
+ *
+ * When @use_defaults is true and the respective property is not found
+ * the following values will be applied:
+ * ->iotype = UPIO_MEM
+ * ->regshift = 0
+ * In this case IRQ must be provided, otherwise an error will be returned.
+ *
+ * The ->irq, ->mapbase, ->mapsize are always altered if no error happened.
+ *
+ * When @use_defaults is false and the respective property is found
+ * the following values will be validated:
+ * - reg-io-width (->iotype)
+ * - reg-offset (->mapsize against ->mapbase)
+ *
+ * Returns: 0 on success or negative errno on failure
+ */
+int uart_read_port_properties(struct uart_port *port, bool use_defaults)
+{
+ struct device *dev = port->dev;
+ u32 value;
+ int ret;
+
+ /* Read optional UART functional clock frequency */
+ device_property_read_u32(dev, "clock-frequency", &port->uartclk);
+
+ /* Read the registers alignment (default: 8-bit) */
+ ret = device_property_read_u32(dev, "reg-shift", &value);
+ if (ret)
+ port->regshift = use_defaults ? 0 : port->regshift;
+ else
+ port->regshift = value;
+
+ /* Read the registers I/O access type (default: MMIO 8-bit) */
+ ret = device_property_read_u32(dev, "reg-io-width", &value);
+ if (ret) {
+ port->iotype = use_defaults ? UPIO_MEM : port->iotype;
+ } else {
+ switch (value) {
+ case 1:
+ port->iotype = UPIO_MEM;
+ break;
+ case 2:
+ port->iotype = UPIO_MEM16;
+ break;
+ case 4:
+ port->iotype = device_is_big_endian(dev) ? UPIO_MEM32BE : UPIO_MEM32;
+ break;
+ default:
+ if (!use_defaults) {
+ dev_err(dev, "Unsupported reg-io-width (%u)\n", value);
+ return -EINVAL;
+ }
+ port->iotype = UPIO_UNSET;
+ break;
+ }
+ }
+
+ /* Read the address mapping base offset (default: no offset) */
+ ret = device_property_read_u32(dev, "reg-offset", &value);
+ if (ret)
+ value = 0;
+
+ /* Check for shifted address mapping overflow */
+ if (!use_defaults && port->mapsize < value) {
+ dev_err(dev, "reg-offset %u exceeds region size %pa\n", value, &port->mapsize);
+ return -EINVAL;
+ }
+
+ port->mapbase += value;
+ port->mapsize -= value;
+
+ /* Read optional FIFO size */
+ device_property_read_u32(dev, "fifo-size", &port->fifosize);
+
+ if (device_property_read_bool(dev, "no-loopback-test"))
+ port->flags |= UPF_SKIP_TEST;
+
+ /* Get index of serial line, if found in DT aliases */
+ ret = of_alias_get_id(dev_of_node(dev), "serial");
+ if (ret >= 0)
+ port->line = ret;
+
+ if (dev_is_platform(dev))
+ ret = platform_get_irq(to_platform_device(dev), 0);
+ else
+ ret = fwnode_irq_get(dev_fwnode(dev), 0);
+ if (ret == -EPROBE_DEFER)
+ return ret;
+ if (ret > 0)
+ port->irq = ret;
+ else if (use_defaults)
+ /* By default IRQ support is mandatory */
+ return ret;
+ else
+ port->irq = 0;
+
+ port->flags |= UPF_SHARE_IRQ;
+
+ return 0;
+}
+EXPORT_SYMBOL(uart_read_port_properties);
+
static struct device_driver serial_port_driver = {
.name = "port",
.suppress_bind_attrs = true,
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 2b0526ae1fac..c93d775fc8a8 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -962,6 +962,7 @@ int uart_register_driver(struct uart_driver *uart);
void uart_unregister_driver(struct uart_driver *uart);
int uart_add_one_port(struct uart_driver *reg, struct uart_port *port);
void uart_remove_one_port(struct uart_driver *reg, struct uart_port *port);
+int uart_read_port_properties(struct uart_port *port, bool use_defaults);
bool uart_match_port(const struct uart_port *port1,
const struct uart_port *port2);

--
2.43.0.rc1.1.gbec44491f096