From 53a3befb692a34ef84047a0fe3320a0ec04d8d9d Mon Sep 17 00:00:00 2001
From: Michael Brown <mcb30@ipxe.org>
Date: Sat, 21 Jun 2025 23:13:58 +0100
Subject: [PATCH] [dwuart] Add a basic driver for the Synopsys DesignWare UART

Signed-off-by: Michael Brown <mcb30@ipxe.org>
---
 src/drivers/uart/dwuart.c  | 120 +++++++++++++++++++++++++++++++++++++
 src/include/ipxe/errfile.h |   1 +
 2 files changed, 121 insertions(+)
 create mode 100644 src/drivers/uart/dwuart.c

diff --git a/src/drivers/uart/dwuart.c b/src/drivers/uart/dwuart.c
new file mode 100644
index 000000000..bf83afd80
--- /dev/null
+++ b/src/drivers/uart/dwuart.c
@@ -0,0 +1,120 @@
+/*
+ * Copyright (C) 2025 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/** @file
+ *
+ * DesignWare UART
+ *
+ */
+
+#include <errno.h>
+#include <ipxe/uart.h>
+#include <ipxe/ns16550.h>
+#include <ipxe/devtree.h>
+#include <ipxe/fdt.h>
+
+/**
+ * Probe devicetree device
+ *
+ * @v dt		Devicetree device
+ * @v offset		Starting node offset
+ * @ret rc		Return status code
+ */
+static int dwuart_probe ( struct dt_device *dt, unsigned int offset ) {
+	struct ns16550_uart *ns16550;
+	struct uart *uart;
+	uint32_t shift;
+	int rc;
+
+	/* Allocate and initialise UART */
+	uart = alloc_uart ( sizeof ( *ns16550 ) );
+	if ( ! uart ) {
+		rc = -ENOMEM;
+		goto err_alloc;
+	}
+	uart->name = dt->name;
+	uart->op = &ns16550_operations;
+	ns16550 = uart->priv;
+	dt_set_drvdata ( dt, uart );
+
+	/* Map registers */
+	ns16550->base = dt_ioremap ( dt, offset, 0, 0 );
+	if ( ! ns16550->base ) {
+		rc = -ENODEV;
+		goto err_ioremap;
+	}
+
+	/* Get register shift */
+	if ( ( rc = fdt_u32 ( &sysfdt, offset, "reg-shift", &shift ) ) != 0 )
+		shift = 0;
+	ns16550->shift = shift;
+
+	/* Register UART */
+	if ( ( rc = uart_register ( uart ) ) != 0 )
+		goto err_register;
+
+	return 0;
+
+	uart_unregister ( uart );
+ err_register:
+	iounmap ( ns16550->base );
+ err_ioremap:
+	uart_nullify ( uart );
+	uart_put ( uart );
+ err_alloc:
+	return rc;
+}
+
+/**
+ * Remove devicetree device
+ *
+ * @v dt		Devicetree device
+ */
+static void dwuart_remove ( struct dt_device *dt ) {
+	struct uart *uart = dt_get_drvdata ( dt );
+	struct ns16550_uart *ns16550 = uart->priv;
+
+	/* Unregister UART */
+	uart_unregister ( uart );
+
+	/* Free UART */
+	iounmap ( ns16550->base );
+	uart_nullify ( uart );
+	uart_put ( uart );
+}
+
+/** DesignWare UART compatible model identifiers */
+static const char * dwuart_ids[] = {
+	"snps,dw-apb-uart",
+};
+
+/** DesignWare UART devicetree driver */
+struct dt_driver dwuart_driver __dt_driver = {
+	.name = "dwuart",
+	.ids = dwuart_ids,
+	.id_count = ( sizeof ( dwuart_ids ) / sizeof ( dwuart_ids[0] ) ),
+	.probe = dwuart_probe,
+	.remove = dwuart_remove,
+};
diff --git a/src/include/ipxe/errfile.h b/src/include/ipxe/errfile.h
index 1a39af43f..9eaa784fc 100644
--- a/src/include/ipxe/errfile.h
+++ b/src/include/ipxe/errfile.h
@@ -110,6 +110,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_nvsvpd		     ( ERRFILE_DRIVER | 0x00140000 )
 #define ERRFILE_uart		     ( ERRFILE_DRIVER | 0x00150000 )
 #define ERRFILE_ns16550		     ( ERRFILE_DRIVER | 0x00160000 )
+#define ERRFILE_dwuart		     ( ERRFILE_DRIVER | 0x00170000 )
 
 #define ERRFILE_3c509		     ( ERRFILE_DRIVER | 0x00200000 )
 #define ERRFILE_bnx2		     ( ERRFILE_DRIVER | 0x00210000 )