serial: serial_xen: Add Xen PV serial driver

Add support for Xen para-virtualized serial driver. This
driver fully supports serial console for the virtual machine.

Please note that as the driver is initialized late, so no banner
nor memory size is visible.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Anastasiia Lukianenko <anastasiia_lukianenko@epam.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

3 files changed, 190 insertions, 0 deletions

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index e146ffc5f8..e344677f91 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -822,6 +822,13 @@ config MPC8XX_CONS
 	depends on MPC8xx
 	default y
 
+config XEN_SERIAL
+	bool "XEN serial support"
+	depends on XEN
+	help
+	  If built without DM support, then requires Xen
+	  to be built with CONFIG_VERBOSE_DEBUG.
+
 choice
 	prompt "Console port"
 	default 8xx_CONS_SMC1
diff --git a/drivers/serial/Makefile b/drivers/serial/Makefile
index e4a92bbbb7..25f7f8d342 100644
--- a/drivers/serial/Makefile
+++ b/drivers/serial/Makefile
@@ -70,6 +70,7 @@ obj-$(CONFIG_OWL_SERIAL) += serial_owl.o
 obj-$(CONFIG_OMAP_SERIAL) += serial_omap.o
 obj-$(CONFIG_MTK_SERIAL) += serial_mtk.o
 obj-$(CONFIG_SIFIVE_SERIAL) += serial_sifive.o
+obj-$(CONFIG_XEN_SERIAL) += serial_xen.o
 
 ifndef CONFIG_SPL_BUILD
 obj-$(CONFIG_USB_TTY) += usbtty.o
diff --git a/drivers/serial/serial_xen.c b/drivers/serial/serial_xen.c
new file mode 100644
index 0000000000..ba6504b947
--- /dev/null
+++ b/drivers/serial/serial_xen.c
@@ -0,0 +1,182 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * (C) 2018 NXP
+ * (C) 2020 EPAM Systems Inc.
+ */
+#include <common.h>
+#include <cpu_func.h>
+#include <dm.h>
+#include <serial.h>
+#include <watchdog.h>
+
+#include <linux/bug.h>
+
+#include <xen/hvm.h>
+#include <xen/events.h>
+
+#include <xen/interface/sched.h>
+#include <xen/interface/hvm/hvm_op.h>
+#include <xen/interface/hvm/params.h>
+#include <xen/interface/io/console.h>
+#include <xen/interface/io/ring.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+u32 console_evtchn;
+
+/*
+ * struct xen_uart_priv - Structure representing a Xen UART info
+ * @intf:    Console I/O interface for Xen guest OSes
+ * @evtchn:  Console event channel
+ */
+struct xen_uart_priv {
+	struct xencons_interface *intf;
+	u32 evtchn;
+};
+
+int xen_serial_setbrg(struct udevice *dev, int baudrate)
+{
+	return 0;
+}
+
+static int xen_serial_probe(struct udevice *dev)
+{
+	struct xen_uart_priv *priv = dev_get_priv(dev);
+	u64 val = 0;
+	unsigned long gfn;
+	int ret;
+
+	ret = hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN, &val);
+	if (ret < 0 || val == 0)
+		return ret;
+
+	priv->evtchn = val;
+	console_evtchn = val;
+
+	ret = hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &val);
+	if (ret < 0)
+		return ret;
+
+	if (!val)
+		return -EINVAL;
+
+	gfn = val;
+	priv->intf = (struct xencons_interface *)(gfn << XEN_PAGE_SHIFT);
+
+	return 0;
+}
+
+static int xen_serial_pending(struct udevice *dev, bool input)
+{
+	struct xen_uart_priv *priv = dev_get_priv(dev);
+	struct xencons_interface *intf = priv->intf;
+
+	if (!input || intf->in_cons == intf->in_prod)
+		return 0;
+
+	return 1;
+}
+
+static int xen_serial_getc(struct udevice *dev)
+{
+	struct xen_uart_priv *priv = dev_get_priv(dev);
+	struct xencons_interface *intf = priv->intf;
+	XENCONS_RING_IDX cons;
+	char c;
+
+	while (intf->in_cons == intf->in_prod)
+		mb(); /* wait */
+
+	cons = intf->in_cons;
+	mb();			/* get pointers before reading ring */
+
+	c = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];
+
+	mb();			/* read ring before consuming */
+	intf->in_cons = cons;
+
+	notify_remote_via_evtchn(priv->evtchn);
+
+	return c;
+}
+
+static int __write_console(struct udevice *dev, const char *data, int len)
+{
+	struct xen_uart_priv *priv = dev_get_priv(dev);
+	struct xencons_interface *intf = priv->intf;
+	XENCONS_RING_IDX cons, prod;
+	int sent = 0;
+
+	cons = intf->out_cons;
+	prod = intf->out_prod;
+	mb(); /* Update pointer */
+
+	WARN_ON((prod - cons) > sizeof(intf->out));
+
+	while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
+		intf->out[MASK_XENCONS_IDX(prod++, intf->out)] = data[sent++];
+
+	mb(); /* Update data before pointer */
+	intf->out_prod = prod;
+
+	if (sent)
+		notify_remote_via_evtchn(priv->evtchn);
+
+	return sent;
+}
+
+static int write_console(struct udevice *dev, const char *data, int len)
+{
+	/*
+	 * Make sure the whole buffer is emitted, polling if
+	 * necessary.  We don't ever want to rely on the hvc daemon
+	 * because the most interesting console output is when the
+	 * kernel is crippled.
+	 */
+	while (len) {
+		int sent = __write_console(dev, data, len);
+
+		data += sent;
+		len -= sent;
+
+		if (unlikely(len))
+			HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
+	}
+
+	return 0;
+}
+
+static int xen_serial_putc(struct udevice *dev, const char ch)
+{
+	write_console(dev, &ch, 1);
+
+	return 0;
+}
+
+static const struct dm_serial_ops xen_serial_ops = {
+	.putc = xen_serial_putc,
+	.getc = xen_serial_getc,
+	.pending = xen_serial_pending,
+};
+
+#if CONFIG_IS_ENABLED(OF_CONTROL)
+static const struct udevice_id xen_serial_ids[] = {
+	{ .compatible = "xen,xen" },
+	{ }
+};
+#endif
+
+U_BOOT_DRIVER(serial_xen) = {
+	.name			= "serial_xen",
+	.id			= UCLASS_SERIAL,
+#if CONFIG_IS_ENABLED(OF_CONTROL)
+	.of_match		= xen_serial_ids,
+#endif
+	.priv_auto_alloc_size	= sizeof(struct xen_uart_priv),
+	.probe			= xen_serial_probe,
+	.ops			= &xen_serial_ops,
+#if !CONFIG_IS_ENABLED(OF_CONTROL)
+	.flags			= DM_FLAG_PRE_RELOC,
+#endif
+};
+