[PATCH 2/2] serial: 8250: Add support for 8250/16550 as MFD function

Esben Haabendal
2019-04-26T08:40:54Z

The serial8250-mfd driver is for adding 8250/16550 UART ports as functions
to an MFD driver.

When calling mfd_add_device(), platform_data should be a pointer to a
struct plat_serial8250_port, with proper settings like .flags, .type,
.iotype, .regshift and .uartclk. Memory (or ioport) and IRQ should be
passed as cell resources.

Do not include UPF_BOOT_AUTOCONF in platform_data.flags.

Signed-off-by: Esben Haabendal <esben@geanix.com>
---
drivers/tty/serial/8250/8250_mfd.c | 119 +++++++++++++++++++++++++++++++++++++
drivers/tty/serial/8250/Kconfig | 12 ++++
drivers/tty/serial/8250/Makefile | 1 +
3 files changed, 132 insertions(+)
create mode 100644 drivers/tty/serial/8250/8250_mfd.c

diff --git a/drivers/tty/serial/8250/8250_mfd.c b/drivers/tty/serial/8250/8250_mfd.c
new file mode 100644
index 0000000..eae1566
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_mfd.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Serial Port driver for 8250/16550-type MFD sub devices
+ *
+ * This mimics the serial8250_probe of 8250_core.c, while allowing
+ * use without UPF_BOOT_AUTOCONF, which is problematic for MFD, as
+ * the request_mem_region() will typically fail as the region is
+ * already requested by the MFD device.
+ *
+ * Memory and irq are passed as platform resources, which allows easy
+ * use together with (devm_)mfd_add_devices().
+ *
+ * Other parameters are passed as struct plat_serial8250_port in
+ * device platform_data.
+ */
+
+#include <linux/platform_device.h>
+#include <linux/module.h>
+#include <linux/io.h>
+#include <linux/serial_8250.h>
+
+struct serial8250_mfd_data {
+ int line;
+};
+
+static int serial8250_mfd_probe(struct platform_device *pdev)
+{
+ struct plat_serial8250_port *pdata = dev_get_platdata(&pdev->dev);
+ struct serial8250_mfd_data *data;
+ struct uart_8250_port up;
+ struct resource *r;
+ void __iomem *membase;
+
+ if (!pdata)
+ return -ENODEV;
+
+ memset(&up, 0, sizeof(up));
+
+ switch (pdata->iotype) {
+ case UPIO_AU:
+ case UPIO_TSI:
+ case UPIO_MEM32:
+ case UPIO_MEM32BE:
+ case UPIO_MEM16:
+ case UPIO_MEM:
+ r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!r)
+ return -ENODEV;
+ membase = devm_ioremap_nocache(&pdev->dev,
+ r->start, resource_size(r));
+ if (!membase)
+ return -ENOMEM;
+ up.port.mapbase = r->start;
+ up.port.membase = membase;
+ break;
+ case UPIO_HUB6:
+ case UPIO_PORT:
+ r = platform_get_resource(pdev, IORESOURCE_IO, 0);
+ if (!r)
+ return -ENODEV;
+ up.port.iobase = r->start;
+ break;
+ }
+
+ data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ up.port.irq = platform_get_irq(pdev, 0);
+ if (up.port.irq < 0)
+ up.port.irq = 0; /* no interrupt -> use polling */
+
+ /* Register with 8250_core.c */
+ up.port.irqflags = pdata->irqflags;
+ up.port.uartclk = pdata->uartclk;
+ up.port.regshift = pdata->regshift;
+ up.port.iotype = pdata->iotype;
+ up.port.flags = pdata->flags;
+ up.port.hub6 = pdata->hub6;
+ up.port.private_data = pdata->private_data;
+ up.port.type = pdata->type;
+ up.port.serial_in = pdata->serial_in;
+ up.port.serial_out = pdata->serial_out;
+ up.port.handle_irq = pdata->handle_irq;
+ up.port.handle_break = pdata->handle_break;
+ up.port.set_termios = pdata->set_termios;
+ up.port.set_ldisc = pdata->set_ldisc;
+ up.port.get_mctrl = pdata->get_mctrl;
+ up.port.pm = pdata->pm;
+ up.port.dev = &pdev->dev;
+ data->line = __serial8250_register_8250_port(&up, 0);
+ if (data->line < 0)
+ return data->line;
+
+ platform_set_drvdata(pdev, data);
+ return 0;
+}
+
+static int serial8250_mfd_remove(struct platform_device *pdev)
+{
+ struct serial8250_mfd_data *data = platform_get_drvdata(pdev);
+
+ serial8250_unregister_port(data->line);
+ return 0;
+}
+
+static struct platform_driver serial8250_mfd_driver = {
+ .probe = serial8250_mfd_probe,
+ .remove = serial8250_mfd_remove,
+ .driver = {
+ .name = "serial8250-mfd",
+ },
+};
+
+module_platform_driver(serial8250_mfd_driver);
+
+MODULE_AUTHOR("Esben Haabendal <esben@geanix.com>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Driver for 8250/16550-type MFD sub devices");
diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index 15c2c54..ef1572b 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -58,6 +58,18 @@ config SERIAL_8250_PNP
This builds standard PNP serial support. You may be able to
disable this feature if you only need legacy serial support.

+config SERIAL_8250_MFD
+ bool "8250/16550 MFD function support"
+ depends on SERIAL_8250 && MFD_CORE
+ default n
+ help
+ This builds support for using 8250/16550-type UARTs as MFD
+ functions.
+
+ MFD drivers needing this should select it automatically.
+
+ If unsure, say N.
+
config SERIAL_8250_FINTEK
bool "Support for Fintek F81216A LPC to 4 UART RS485 API"
depends on SERIAL_8250
diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
index 18751bc..da8e139 100644
--- a/drivers/tty/serial/8250/Makefile
+++ b/drivers/tty/serial/8250/Makefile
@@ -6,6 +6,7 @@
obj-$(CONFIG_SERIAL_8250) += 8250.o 8250_base.o
8250-y := 8250_core.o
8250-$(CONFIG_SERIAL_8250_PNP) += 8250_pnp.o
+8250-$(CONFIG_SERIAL_8250_MFD) += 8250_mfd.o
8250_base-y := 8250_port.o
8250_base-$(CONFIG_SERIAL_8250_DMA) += 8250_dma.o
8250_base-$(CONFIG_SERIAL_8250_FINTEK) += 8250_fintek.o
--
2.4.11