tty: serial: 8250: add DFL bus driver for Altera 16550.

Add a Device Feature List (DFL) bus driver for the Altera
16550 implementation of UART.

Signed-off-by: Matthew Gerlach <[e-mail]>
Reviewed-by: Ilpo Järvinen <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
Reviewed-by: Marco Pagani <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/8250/8250_dfl.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for FPGA UART
+ *
+ * Copyright (C) 2022 Intel Corporation.
+ *
+ * Authors:
+ *   Ananda Ravuri <[e-mail]>
+ *   Matthew Gerlach <[e-mail]>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/device.h>
+#include <linux/dfl.h>
+#include <linux/errno.h>
+#include <linux/ioport.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/types.h>
+
+#include <linux/serial.h>
+#include <linux/serial_8250.h>
+
+#define DFHv1_PARAM_ID_CLK_FRQ    0x2
+#define DFHv1_PARAM_ID_FIFO_LEN   0x3
+
+#define DFHv1_PARAM_ID_REG_LAYOUT	0x4
+#define DFHv1_PARAM_REG_LAYOUT_WIDTH	GENMASK_ULL(63, 32)
+#define DFHv1_PARAM_REG_LAYOUT_SHIFT	GENMASK_ULL(31, 0)
+
+struct dfl_uart {
+	int line;
+};
+
+static int dfh_get_u64_param_val(struct dfl_device *dfl_dev, int param_id, u64 *pval)
+{
+	size_t psize;
+	u64 *p;
+
+	p = dfh_find_param(dfl_dev, param_id, &psize);
+	if (IS_ERR(p))
+		return PTR_ERR(p);
+
+	if (psize != sizeof(*pval))
+		return -EINVAL;
+
+	*pval = *p;
+
+	return 0;
+}
+
+static int dfl_uart_get_params(struct dfl_device *dfl_dev, struct uart_8250_port *uart)
+{
+	struct device *dev = &dfl_dev->dev;
+	u64 fifo_len, clk_freq, reg_layout;
+	u32 reg_width;
+	int ret;
+
+	ret = dfh_get_u64_param_val(dfl_dev, DFHv1_PARAM_ID_CLK_FRQ, &clk_freq);
+	if (ret)
+		return dev_err_probe(dev, ret, "missing CLK_FRQ param\n");
+
+	uart->port.uartclk = clk_freq;
+
+	ret = dfh_get_u64_param_val(dfl_dev, DFHv1_PARAM_ID_FIFO_LEN, &fifo_len);
+	if (ret)
+		return dev_err_probe(dev, ret, "missing FIFO_LEN param\n");
+
+	switch (fifo_len) {
+	case 32:
+		uart->port.type = PORT_ALTR_16550_F32;
+		break;
+
+	case 64:
+		uart->port.type = PORT_ALTR_16550_F64;
+		break;
+
+	case 128:
+		uart->port.type = PORT_ALTR_16550_F128;
+		break;
+
+	default:
+		return dev_err_probe(dev, -EINVAL, "unsupported FIFO_LEN %llu\n", fifo_len);
+	}
+
+	ret = dfh_get_u64_param_val(dfl_dev, DFHv1_PARAM_ID_REG_LAYOUT, &reg_layout);
+	if (ret)
+		return dev_err_probe(dev, ret, "missing REG_LAYOUT param\n");
+
+	uart->port.regshift = FIELD_GET(DFHv1_PARAM_REG_LAYOUT_SHIFT, reg_layout);
+	reg_width = FIELD_GET(DFHv1_PARAM_REG_LAYOUT_WIDTH, reg_layout);
+	switch (reg_width) {
+	case 4:
+		uart->port.iotype = UPIO_MEM32;
+		break;
+
+	case 2:
+		uart->port.iotype = UPIO_MEM16;
+		break;
+
+	default:
+		return dev_err_probe(dev, -EINVAL, "unsupported reg-width %u\n", reg_width);
+
+	}
+
+	return 0;
+}
+
+static int dfl_uart_probe(struct dfl_device *dfl_dev)
+{
+	struct device *dev = &dfl_dev->dev;
+	struct uart_8250_port uart = { };
+	struct dfl_uart *dfluart;
+	int ret;
+
+	uart.port.flags = UPF_IOREMAP;
+	uart.port.mapbase = dfl_dev->mmio_res.start;
+	uart.port.mapsize = resource_size(&dfl_dev->mmio_res);
+
+	ret = dfl_uart_get_params(dfl_dev, &uart);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "failed uart feature walk\n");
+
+	if (dfl_dev->num_irqs == 1)
+		uart.port.irq = dfl_dev->irqs[0];
+
+	dfluart = devm_kzalloc(dev, sizeof(*dfluart), GFP_KERNEL);
+	if (!dfluart)
+		return -ENOMEM;
+
+	dfluart->line = serial8250_register_8250_port(&uart);
+	if (dfluart->line < 0)
+		return dev_err_probe(dev, dfluart->line, "unable to register 8250 port.\n");
+
+	dev_set_drvdata(dev, dfluart);
+
+	return 0;
+}
+
+static void dfl_uart_remove(struct dfl_device *dfl_dev)
+{
+	struct dfl_uart *dfluart = dev_get_drvdata(&dfl_dev->dev);
+
+	serial8250_unregister_port(dfluart->line);
+}
+
+#define FME_FEATURE_ID_UART 0x24
+
+static const struct dfl_device_id dfl_uart_ids[] = {
+	{ FME_ID, FME_FEATURE_ID_UART },
+	{ }
+};
+MODULE_DEVICE_TABLE(dfl, dfl_uart_ids);
+
+static struct dfl_driver dfl_uart_driver = {
+	.drv = {
+		.name = "dfl-uart",
+	},
+	.id_table = dfl_uart_ids,
+	.probe = dfl_uart_probe,
+	.remove = dfl_uart_remove,
+};
+module_dfl_driver(dfl_uart_driver);
+
+MODULE_DESCRIPTION("DFL Intel UART driver");
+MODULE_AUTHOR("Intel Corporation");
+MODULE_LICENSE("GPL");

drivers/tty/serial/8250/Kconfig

···
 	  erratum for Freescale 16550 UARTs in the 8250 driver. It also
 	  enables support for ACPI enumeration.
 
+config SERIAL_8250_DFL
+	tristate "DFL bus driver for Altera 16550 UART"
+	depends on SERIAL_8250 && FPGA_DFL
+	help
+	  This option enables support for a Device Feature List (DFL) bus
+	  driver for the Altera 16550 UART. One or more Altera 16550 UARTs
+	  can be instantiated in a FPGA and then be discovered during
+	  enumeration of the DFL bus.
+
+	  To compile this driver as a module, chose M here: the
+	  module will be called 8250_dfl.
+
 config SERIAL_8250_DW
 	tristate "Support for Synopsys DesignWare 8250 quirks"
 	depends on SERIAL_8250

drivers/tty/serial/8250/Makefile

···
 obj-$(CONFIG_SERIAL_8250_HUB6)		+= 8250_hub6.o
 obj-$(CONFIG_SERIAL_8250_FSL)		+= 8250_fsl.o
 obj-$(CONFIG_SERIAL_8250_MEN_MCB)	+= 8250_men_mcb.o
+obj-$(CONFIG_SERIAL_8250_DFL)		+= 8250_dfl.o
 obj-$(CONFIG_SERIAL_8250_DW)		+= 8250_dw.o
 obj-$(CONFIG_SERIAL_8250_EM)		+= 8250_em.o
 obj-$(CONFIG_SERIAL_8250_IOC3)		+= 8250_ioc3.o